Sean Gold Design Techniques Electrostatic Discharge Protection Se
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THIS ISSUE COVER ARTICLE Design Techniques Electrostatic Discharge Protection.
Sean Gold
Design Techniques Electrostatic Discharge Protection Sean Gold
Since their infancy, integratedcircuit manufacturers have been concerned about circuit damage caused electrostatic discharge (ESD). Assembly packaging procedures often proved fatal early stone-knife bearskin ICs. Design processing techniques improved, device geometries shrank, perpetuating problems. Today, interest protection goes beyond handling assembly considerations. Portable computers instrumentation often subjected severe electrical stresses, imposing stringent demands exposed circuitry. Digitalcommunication interfaces input amplifiers must tolerate repetitive pulses because cable connections frequently come contact with humans other charged bodies. addition, products sold European markets must conform standards forth European Committee Electrotechnical Standardization (CENELEC). standard ESD, IEC-801-2, under review will become mandatory 1996. Inductively, when surface becomes polarized nearby electric fields Capacitively, when capacitance body fixed potential increases Triboelectrically, when materials exchange charge result friction separated.1 third generation mechanism, triboelectricity, usually most troublesome because human body acquire substantial charge, 35kV some cases, depending upon relative humidity electrical properties materials involved. Walking across wool carpet with leather shoes winter generate charge 10kV 15kV, whereas same action humid summer produce less than 2kV.
Editor's Page
Richard Markell
DESIGN FEATURES LT1190 Family Ultra-High-Speed Amps Eclipse Prior
John Wright Mitchell
LTC1196/1198 ADCs Beat Half-Flashes Supplies
William Rempfer Marco
DESIGN INFORMATION LT1112/LT1114 Dual/Quad Precision Amps have Universal Appeal
George Erdi
LTC1157 Dual 3.3V Micropower MOSFET Driver
Skovmand
World's Lowest-Noise Available UnityGain Stable Versions
George Erdi Alexander Strong
Charge Transfer
charge affect circuitry, must transferred from generator. Electrostatic charge transferred between bodies different potentials directly, physical contact, inductively, electrostatic field.
DESIGN IDEAS Temperature-Compensated, Voltage-Controlled-Gain Amplifier Using LT1228
Frank
UNDERSTANDING
Even though most modern have some form protection, basic understanding electrostatic discharge, causes remedies, helpful when designing circuits electrically harsh environments.
Flash-Memory Generator
Sean Gold
Bias Supply.
Steve Pietkiewicz
Charge Generation
Both conductors insulators support charge, which build three ways:
Device Cameos
OMPL
90ANT
continued page
EDITOR'S PAGE DESIGN FEATURES
Protection, High-Speed Precision Amps, Fast Serial ADCs Highlight this Issue Richard Markell
This issue, last year, spotlights many different topics. (electrostatic discharge) critical issue most RS232 designs. lead article presents careful study causes, cures, prevention electrostatic-discharge damage RS232 circuitry. article presents method virtually assure that your RS232 design best expended time resources intensive program ensure that RS232 devices resistant make them. Laboratory testing proven that RS232 devices withstand multiple 10kV strikes. Line drivers line receivers must more resistant than other types devices since their inputs outputs connect directly outside world. Other devices hidden inside instrumentation boxes, boards, otherwise shielded from rigors experienced DB25 (RS232) connector. Making LTC's RS232 parts more rugged tune 10kV another engineering triumph from designers LTC. This issue includes articles high-speed operational amplifiers. first collection circuits designed around cost LT1190 video amplifier. second shows temperature compensation LT1228 electronic gain control amplifier. Both these components whole list other video amplifiers products from LTC's 600MHz complementary bipolar process. This proprietary process allows designers combine precision specifications with high speed, resulting some best video amplifiers industry. Watch more video amplifiers other high-speed products from LTC. Precision operational amplifiers also well represented this issue with articles LT1112/1114 dual quad surface-mountable amps. Also world amps surface-mount version industry's lowest noise amp, LT1028. addition, LT1128 unitygain-stable version LT1028, which also available packages. LT1028 LT1128 featured short article herein. Last described here, certainly least performance, converters. These converters, LT1196/1198, challenge half-flash converters speed, cost, power consumption, size, ease use.
Issue Highlights
Sean Gold leads this issue with article techniques staving horrors ESD. Sean been four years, during which time designed LT1134, LT1137, LT1237, LT1330, LT1026 LT1116. avid cyclist, urban adventurer, alpine skier, regularly attends Foothill College electronics flea market. Sean's collection mid-60's oscilloscopes instrumentation made extremely popular with ladies. Mitchell John Wright describe number applications LTC's LT1190 high-speed amp. Mitchell been years Applications Engineer. worked semiconductor applications arena (and certainly arena) more than years total. Mitchell's hobbies include fourth-sea2
mountaineering music. Unlike John, Mitchell doesn't fish Creek. Frank newest member Applications Group. Frank describes LT1228 100MHz current-feedback amplifier with gain control. been involved video systems past eight years. Frank been only four months already developing many video circuits using LTC's high-speed operational amplifiers. Frank's outside interests include fishing audio systems. Alexander Strong George Erdi describe some offerings amps, LT1128 LT1028 packaging. Alex been more than years. worked semiconductor industry more than years, primarily designing
amps converters. Alex Vermont native whose interests include camping, hiking, racing diesel Mercedes Laguna Seca. Alex another loyal patron Foothill flea market. Marco designer coauthor article LTC1196/ 1198 serial 8-bit converters that convert speeds 1.3MHz. Marco been five years been industry total eight years. designed LTC690 series microprocessor supervisory circuits, LTC1096, LTC1098, LTC1196 LTC1198. Marco's outside interests include family, gardening, home improvement. Short biographies John Wright, Willie Rempfer, George Erdi appeared previous issues.
Linear Technology Magazine October 1992
DESIGN FEATURES
LT1190 Family Ultra-High-Speed Amps Eclipse Prior John Wright
Mitchell
Introduction
LT1190 series amps combine bandwidth, slew rate, output-drive capability satisfy demands many high-speed applications. This family offers 350MHz gain-bandwidth product, slew rates 450V/µs, drives (75, double-terminated) load. systems, LT1190 family deliver +13.5dBm doubleterminated load. These parts based familiar, easy-to-use, voltagemode feedback topology. Characteristics three members LT1190 series shown Table
Table Characteristics LT1190 family
2dB/DIV
2dB/DIV
LT1191 LM118 100M 100k LM118 LT1190 LT1191
100k LT1190
TIME
TIME
100M
Figure Small-signal response 1190_1.= 130MHz peaking socket bypass components
Figure Small-signal response 1190_2.=
Small-Signal Performance
Settling Time (V/µs) Gain (0.1%,
Part LT1190 LT1191 LT1192
GBWP (MHz)
LT1190 series devices operate single supplies, split supplies ±8V. Output current capability ±50mA. Careful chip design made LT1190 family quite tolerant supplyrail bypassing. many applications, simple 100nF disc ceramic capacitor from each supply ground that needed. Where settling time issue, 4.7µF tantalum capacitor should added each supply pin. Such cavalier attitude toward supply bypassing radical departure from industry norm. Another unusual feature common LT1190 family shutdown. This allows user multiplex outputs, gate signals, conserve power when idle.
Figures show smallsignal performance LT1190 LT1191 when configured gains non-inverting plots show peaking 130MHz, which characteristic socketed test fixture supply bypass components. tight PC-board layout would reduce LT1190 peaking 2dB. smallsignal performance LM118 shown comparison.
must deliver large currents into capacitive load detector. Other problems include amplifier instability with large capacitive loads preservation output-voltage accuracy.
Detecting Sine Waves
LT1190 ideal candidate this application, with 450V/µs slew rate, 50mA output current, phase margin. closed-loop peak detector circuit Figure uses Schottky diode inside feedback loop obtain good accuracy. resistor (RO) isolates 10nF load prevents oscillation. error with sine-wave input plotted Figure various input amplitudes. value read with DVM. frequencies, error small dominated decay detector capacitor between cycles.
Applications
Fast peak detectors place unusual demands amplifiers. output stage must have high slew rate order keep with intermediate stages amplifier. This condition causes either long overload DCaccuracy errors. maintain high slew rate output, amplifier
LT1190
1N5712 10nF
1190_3.A
Figure Closed-loop peak detector
Linear Technology Magazine October 1992
DESIGN FEATURES
LM118 2VP-P SLEW RATE LIMIT LT1190 4VP-P LT1190 2VP-P
DETECTOR ERROR
LT1190 1N5712
1N5712
10nF
LT1190 6VP-P 100k
1190_4.
1190_5.
Figure Open-loop, high-speed peak detector
20pF
FREQUENCY (Hz)
Figure Closed-loop peak-detector error frequency
LT1190
1N5712
SCHOTTKY 2VP-P
LM118 2VP-P
1N5712
DETECTOR ERROR
LT1190 SCHOTTKY 4VP-P 2VP-P 4VP-P SCHOTTKY 6VP-P 6VP-P
1190_7.
Figure Fast pulse detector
FREQUENCY (Hz)
1190_6.
100M
Figure Open-loop peak-detector error frequency
frequency rises, error increases because capacitor charging time decreases. During this time overdrive becomes very small portion sine wave cycle. Finally, approximately 4MHz, error rises rapidly owing slew-rate limitation amp. comparison purposes, error LM118 also plotted 2VP-P. Schottky-diode peak detector built with capacitor pulldown. Although this simple circuit very fast, limited usefulness owing error diode threshold input impedance. accuracy this simple detector improved with LT1190 circuit Figure this open-loop design, detector diode levelshifting compensating diode. load resistor, connected -5V, identical bias resistor, used bias compensating diode. Equal-
value resistors ensure that diode drops equal. values 10k) provide fast response, expense poor low-frequency accuracy. High values provide good lowfrequency accuracy cause amplifier slew-rate limit, resulting poor high-frequency accuracy. good compromise made adding feedback capacitor, CFB, which enhances negative slew rate input. error with sine-wave input, read with DVM, plotted Figure comparison purposes LM118 error plotted, well error simple Schottky detector.
80ns wide. maximum output slew rate photo 70V/µs. This rate 70mA current limit driving 1nF. performance benchmark, LM118 takes 1.2µs peak detect settle, given same amplitude input. This slower response due, part, much lower slew rate lower phase margin LM118.
Instrumentation Amplifier Rejects High Voltage
Instrumentation amplifiers normally used process slowly varying outputs from transducers, rather than
4VP-P dV/dt LIMITING 20pF
DETECTOR ERROR
Pulse Detector
fast pulse detector made with circuit Figure very fast input pulse will exceed amplifier's slew rate cause long overload recovery time. Some amount dV/dt limiting input help this overload condition; however, will delay response. Figure shows detector error versus pulse width. Figure response 4VP-P input pulse that
1190_8.
PULSE WIDTH (ns)
Figure Detector error pulse width
Linear Technology Magazine October 1992
DESIGN FEATURES
(1V/DIV)
120VP-P
LT1192
(1V/DIV)
1190_10.
Figure 3.5MHz instrumentation amplifier rejects 120VP-P
20ns/DIV
1190_9. Figure Open-loop peak detector responseeps Trace output Volt/division) Trace input Volt/division)
75pF 3.579545MHz 75pF 100k LT1190
NETWORK ANALYZER (ZIN
2V/DIV
330pF 1N5711
1N5711
1190_12.
200ns/DIV
Figure High-frequency Colpitts oscillator
1190_11.
Figure Output instrumentation amplifier with 1MHz square wave riding 120VP-P input
fast signals. However, possible make instrumentation amplifier that responds very quickly, with good common mode rejection. circuit Figure LT1192 used obtain 50dB CMRR from 120VP-P signal. this application, CMRR limited matching resistors, which should match better than 0.01%. LT1192 used this application because circuit noise gain 100, because higher gain bandwidth LT1192 allows -3dB bandwidth 3.5MHz. Note also that 100:1 attenuation common-mode signal presents common-mode voltage amplifier only 1.2VP-P. Figure shows amplifier output 1MHz square wave riding 120VP-P, 60Hz signal. circuit exhibits 50dB rejection common-mode signal.
Crystal Oscillator
amps have found wide low-frequency (100kHz) crystal oscillator circuits, just haven't bandwidth operate successfully higher frequencies. LT1190 LT1191 make excellent gain stages high-frequency Colpitts oscillators. practical implementation shown Figure Gain limiting provided Schottky diodes, which maintain output approximately +11dBm- sufficient directly drive +10dBm diode-ring mixers. Output-stage clipping recommended means gain limiting, this increases distortion allows internal nodes overdriven. recovery time would excessive phase shift oscillator loop, degrading frequency stability. Distortion performance good, considering that oscillator consists stage deliver useful output power. Figure shows spectral
plot oscillator's output. second harmonic approximately 37dB down, limited primarily clipping action Schottky diodes. Powersupply rejection excellent, showing frequency sensitivity approximately 0.1ppm/V. LT1190 gives acceptable performance 10MHz, while LT1191 extends circuit's operating range 20MHz.
OUTPUT POWER (dBm)
1190_13.
FREQUENCY (MHz)
Figure Oscillator output spectrum
Linear Technology Magazine October 1992
DESIGN FEATURES
LTC1196/1198 SO-8 Packaged ADCs Beat Half-Flashes Arena Supplies William Rempfer
Marco
INTRODUCTION
LTC1196/1198 600ns, 1.2MHz sampling 8-bit converters packaged tiny 8-pin packages operating supplies. on-chip sample-andholds have full-accuracy input bandwidths 1MHz. ADCs draw only 10mW from supply 50mW from supply LTC1198 powers down leakage current between conversions. LTC1196 differential inputs offers highest sample rate (1.2MHz). LTC1198 converts input channels, single ended differentially. These converters provide system designers with previously impossible levels performance extremely small space. This article will discuss ADCs' advantages, design techniques, performance, application considerations. times wider input-sampling bandwidths than well known half-flash products such AD7821, ADC08061, ML2261. With 600ns conversion times, 1.2MHz sampling rates, 1MHz full-accuracy input bandwidths, LTC1196/1198 more than match half-flash ADCs.
Cost
LTC1196/1198 reduce system cost relative half-flash ADCs number ways. First, they offer tremendous price/performance advantages when their sticker prices compared those half-flash converters this speed range. Second, savings board space translate into cheaper system system that wasn't even possible with older technology. Third, operation eliminate cost regulated supply battery systems cost generating separate supply systems. Fourth, reduced-span operation reduce cost signalconditioning circuitry. Finally, reduced power consumption power shutdown reduce cost system power supply batteries.
Figure LTC1196/1198 (right) provide considerable space savings over half-flash ADCs (left)
SIZE, SPEED, COST, POWER ADVANTAGES
LTC1196/1198 offer smaller size, better speed, lower cost, much lower power dissipation than half-flash converters.
space allows located close signal source, making physical configuration more flexible smaller than 11-wire-I/O halfflash alternatives. With LTC1196/ 1198, extremely small configuration implemented, shown Figure system powered 100% surface mountable.
Speed
LTC1196 LTC1198 beat half-flash ADCs speed. They offer equivalent sample rates three
LTC1196 SUPPLY CURRENT, (mA)
Size
LTC1196/1198 provide considerable space savings over half-flash ADCs three reasons: First, tiny SO-8 package minimum number external components makes ADCs' configuration small compared those 20-pin alternatives. Second, power dissipation high-impedance inputs space requirements power supply signal-conditioning circuitry. Third, serial interface processor, digital ASIC, logic system requires only three wires only three pins receiving system. This saves board
Power
power savings ADCs, especially LTC1198, very large. Their power consumption when operating rail equal that half-flash converter. Power consumption reduced ways. Using supply lowers power consumption both devices factor five, 10mW. LTC1198 reduce power even more because shuts down whenever converting. Figure shows supply current versus sample rate LTC1196 LTC1198
LTC1196 2.7V
LTC1198
0.01
LTC1198 2.7V
0.001
100k
1196_2.
SAMPLE RATE (Hz)
Figure sample rate LTC1196 LTC1198 operating 2.7V supplies
Linear Technology Magazine October 1992
DESIGN FEATURES
30ns SETTLES 20ns COMPARATOR LATCHES VALUE 70ns
1196_3.
20ns UPDATES
Figure Bit-test timing sequence
INTERNAL DESIGN: GETTING HALF-FLASH SPEEDS WITH CONVERTER
LTC1196/1198 design uses successive-approximation technique achieve remarkable speed from low-cost n-well CMOS process. achieve 600ns conversion time 1.2MHz sample rate, tests performed every 70ns. digitize 1MHz input signals full accuracy, sample-and-hold bandwidth 10MHz acquires settles less than 100ns. partitioning 70ns bit-test time shown Figure cycle consists switching settling, comparator making decision, latching value updating DAC. capacitive design settles 0.02% 30ns. design layout critical achieving this speed. settling time constant must less than 3.5ns. comparator ultra-fast, auto-zeroed, sampled-data comparator. redesign comparator used LTC1272 12-bit, sampling ADC. design includes cascaded stages gain extremely wide (200MHz) small-signal bandwidth. designed minimize disturbance power supply lines
responds 0.5mV overdrive 20ns. Figure shows conversion timing LTC1196. conversion takes clock cycles total cycle time clock cycles. These correspond conversion time 600ns sample rate 1.2MHz maximum 14.3MHz clock frequency. sampleand-hold acquires analog input from conversion start next. that time goes into hold mode conversion starts.
APPLICATION CONSIDERATIONS
Analog Considerations
LTC1196/1198 remarkably easy use. They will yield excellent performance some simple rules followed board layout, bypassing, driving reference analog inputs. (For more detailed discussion Linear Technology Volume Number 9-10 LTC1196/ 1198 data sheet.) Board layout should include analog ground plane which analog circuitry referenced. Low-inductance ground supply lines recommended. Also, input signal should routed away from digital circuitry. power supply clean, bypassing requires only 0.1µF capacitor, because power-supply transients produced within chip have been minimized. surface-mount chip cap. ceramic cap. with short leads will give very good results.
continued page
VERSUS PERFORMANCE COMPARISON
performance comparison Table shows that using supply gives great savings power with only modest reductions speed. power dissipation drops factor five when supply reduced converter slows down somewhat still gives excellent performance rail. converts 1.6µs, samples 450kHz, provides 500kHz linear-input bandwidth, making fastest market. Getting power loss makes operation very attractive. Dynamic accuracy excellent both ADCs typically provide 49.3dB 7.9ENOBs (Effective Number Bits) dynamic accuracy both noise floor extremely low, corresponding transition noise less than 0.1LSB. accuracy includes ±0.5LSB total unadjusted error linearity error ±0.5LSB while total unadjusted error increases ±1LSB.
tCYC CLKs)
Table 5V/3V performance comparison
LTC1196/1198 PDISS fSAMPLE tCONV (Max) Typical ENOBs Linear Input Bandwidth (ENOBs
50mW 10mW 1.2MHz 450kHz 600ns 1.6µs 0.5LSB 0.5LSB 300kHz 100kHz 1MHz 500kHz
NULL
DOUT
Hi-Z tSMPL
NULL
Hi-Z tSMPL (3.5 CLKs)
tCONV (8.5 CLKs)
1196_4.
Figure LTC1196 conversion timing
Linear Technology Magazine October 1992
DESIGN FEATURES
1kV/DIV
5ms/DIV
esd_1.eps Figure 3.5kV pulse. (Photo taken with low-capacitance voltage divider type P6103 high-voltage probe)
Figure damage results resistive short from bond thin oxide region unprotected bipolar
ESD, continued from page
human body store millijoules energy, but, because body's relatively high source impedance, that energy transferred during discharge. pulses exhibit slowly decaying exponential response, rise time extremely fast. (Figure often contains frequency components well into range. such frequencies, nearby cables circuit-board traces look like receiving antennas that pick noise.
Damage
Early were especially susceptible ESD-induced oxide damage voltages. Discharges less than 500V, which were commonly generated during assembly handling, were sufficient cause damage. Damage often occurred where oxide's dielectric strength weakest. trouble spots were usually regions where metal from passed over
thin oxide-often diffusion. Recognition this problem improved processing techniques have eliminated this type damage. Damage from fundamentally result transfer energy. Heat destroy junctions metallization when excessive energy dissipates within chip. Intense electrostatic fields also break down junctions thin oxide preceding destructive energy transfer. Figures show some typical examples damage. noise also drive circuitry into invalid locked-up states that necessarily destructive. definition, such "soft errors" corrected cycling power supply forcing circuit back into valid operating state. soft error induces high-current condition, prolonged heating destroy unprotected device. Systems made resilient soft errors using digital control detect invalid states reset circuit.
ment circuit model based charge storage characteristics human body. switching circuit shown Figure consists 100pF high-voltage capacitor discharged through 1.5k resistor. energy delivered load each pulse (1/2)CV L/RS RL). Test equipment based this circuit model used determine tolerances quoted here.
PROTECTION TECHNIQUES
action that eliminates charge generator, circumvents charge transfer, enhances circuit's ability absorb energy will increase circuit's tolerance ESD. Eliminating ubiquitous charge generators disrupting charge transfer difficult tasks because they demand strict control circuit's operating environment. more practical approach limit entry points shielding circuit's enclosure covering exposed connectors when they use. Another practical remedy increase circuit's ability absorb energy clamping exposed pins
1.5k DISCHARGE DISCHARGE SWITCH
Circuit Models
need generate pulses test purposes prompted developRC 100M
HIGH-VOLTAGE SUPPLY
100pF
DISCHARGE RETURN CONNECTION
Figure Removing metallization reveals junction damage between emitter collector lateral transistor
esd_4.eps
Figure Human-body model circuit pulses
Linear Technology Magazine October 1992
DESIGN FEATURES
RS232 TRANSMITTER RS232 RECEIVER
CLAMP
CLAMP
COUPLING CAPACITORS
esd_5.eps
Figure Older interface designs used external clamps
turned powered down. When transceiver significant discharge occurs, resulting current de-bias internal circuitry cause nondestructive soft errors. Observations have shown these errors highly dependent upon logical state transceiver.
RS232 RECEIVER RS232 LINE LOGIC OUTPUT 50pF FERRITE BEADS RS232 DRIVER RS232 LINE LOGIC INPUT 50pF
Filters
ground with fast-acting avalanche diodes dedicated transient suppressors (Figure Discrete suppressors widely available extremely effective. Designers often reluctant discrete suppressors because they expensive-at $0.40/ they sometimes exceed cost Transient suppressors also introduce stray capacitance, which prohibit their high-speed circuits. When extremely high levels protection required, external filter used additional protection. circuit Figure 10MHz cutoff frequency with 40dB/ decade rolloff, which sufficient drop energy into range that safely dissipated within transceiver.
esd_6.eps
Figure External filters provide protection from very high levels ESD, cost less than discrete suppressors
Board Layout
Energy shunted through clamp still cause problems ground path's return inductance large enough create sizable voltage drop. Such voltage drops damage unprotected components that share common ground line. Consider circuit model shown Figure Suppose return path ground presents impedance frequencies. voltage local ground approximately (RG/ RG+RS) VP/1500. there poor common-mode coupling VCC, digital sharing common ground will damaged when exceeds VCC+0.7V. This condition occurs when peak voltage greater than 8.55kV. Using low-inductance ground plane, preferably, isolating return path impedance ground, therefore essential good protection.
Designers often reluctant discrete suppressors because they expensive. they sometimes exceed cost
LT1237 RS232 transceiver incorporates clamps diverting energy chip. These active structures quickly respond positive negative signals threshold voltages higher than RS232 signals below destructive levels device. path high current flow through large junctions, which increase device's capacity absorb energy. LT1237's structures absorb human-body-model discharges >10kV. resulting current flow insignificant when transceiver
Sometimes high current path directly ground. example with LT1237, currents flow through device's substrate, which connected negative charge pump output, coupled ground through 0.1µF storage capacitor, which must have effective series resistance (ESR) prevent damaging voltage drops. Adding hundred picofarads capacitance parallel with primary storage capacitor effectively reduces frequencies. When using discrete transient suppressors filters, place components close possible connector with short paths return plane. Increasing distance, series resistance, between entry point sensitive device diminishes energy transferred. pulses easily from trace another when spacing between traces narrow. Increasing spacing between circuit board traces surrounding signal lines with separate return plane helpful preventing energy from arcing between pins. Arcing occurs slowly compared with rise time, spark gaps
1.5k CLAMP HIGH-VOLTAGE SUPPLY DIGITAL CIRCUITS
EQUIVALENT DECOUPLING NETWORK
PREFERRED RETURN PATH
esd_7.eps
Figure Circuit model current flow
Linear Technology Magazine October 1992
DESIGN FEATURES
this! Instead, couple grounds they shorted frequencies.
Triboelectric charging should confused with primal creatures worship Tektronix oscilloscope, often referred "tribe-o-electricals." References: Linear Technology 1990 Databook, pp.15-23 15-34. Clarke, Neill, "Electrical-Transient Immunity: Growing Imperative System Design," Electronic Design, 1992, 83-98. Boxleitner, "How defeat electrostatic discharge," IEEE Spectrum, August 1989, 36-40. Matisoff, Handbook Electrostatic Discharge Controls, Nostrand Reinhold, 1986.
Isolation
transients should confused with lowfrequency ground faults that occur when circuits with large differences ground poten tial connected together. amount energy transferred during ground fault 0.5ms/DIV vastly greater than Figure 10-mil spark limits duration energy pulse. alone will protect circuitry from guard against ground faults requires ESD. Spark gaps are, fact, useful circuit with true isolation. fully limiting energy. Figure isolated RS232 transceiver design shows 300µs delay between described Linear Technology's initial rise activation Design Note spark gap. connections cable shield CONCLUSION techniques described here canaffect noise performance. Designers feel inclined float entirely eliminate problems, cable shield with respect local understanding ESD's nature ground avoid circulating currents using careful circuit design will help differences ground potential. protect against intrusion.
1kV/DIV
esd_8.eps
Anatomy LT1237 RS232 Port
LT1237 complete RS232 port, designed specifically battery-powered computers instrumentation. device contains three drivers, five receivers, regulated charge pump reduce supply current. Supply current typically 6mA, device shut down with separate logic controls. driver-disable shuts charge pump drivers, leaving receivers active, ISUPPLY 4mA. ON/OFF shuts down circuitry except micropower receiver, ISUPPLY 60µA. active receiver useful detecting start-up signals. LT1237 operates 120kbaud, fully compliant with RS232 specifications fault conditions. flow-through pinout LT1237's ability small surface-mount capacitors helps reduce interface's overall footprint. Connections RS232 cable protected with internal structures that withstand repetitive ±10kV human-body-model pulses.
Linear Technology Magazine October 1992
1.0µF 0.1µF
0.1µF
LT1237
0.1µF 0.1µF
DRIVER DRIVER DRIVER (LOW-Q) DRIVER DISABLE LOGIC
DRIVER DRIVER LINE DRIVER (LOW-Q) ON/OFF
RING DETECT RECEIVE ONLY MODE CONTROLLER SHUTDOWN CONTROL
esd_box.eps
Figure typical application circuit LT1237 under digital control
DESIGN INFORMATION
12/LT1 Dual/Quad Precision Amps have Universal Appeal George Erdi
LT1112 LT1114 dual quad universal precision amps. universal description justified fact that important precision specifications have been optimized: Microvolt offset voltage: cost grades (including smalloutline, 8-pin surface-mount package) guaranteed 75µV Drift guaranteed 0.5µV/°C (0.75µV/°C cost grades) Bias offset currents picoampere range, even 125°C noise: 0.32µV peak-to-peak, 0.1Hz 10Hz Supply current 400µA max. amplifier Voltage gain excess million Therefore, there very precision op-amp applications, where LT1112/LT1114 will dual quad choice. They stocked universal dual quad used without time-consuming error-budget calculations. Table lists guaranteed specifications.
Table LT1112 dual, LT1114 quad low-cost grades, guaranteed specifications ±15V, 25°C
VIEW PACKAGE 8-LEAD PLASTIC SOIC LT1112S8 PACKAGE 8-LEAD PLASTIC SOIC LT1013DS8 LT1057S8 LT1078S8 LT1124CS8 LT1126CS8
1112_1.eps
VIEW
Figure Standard configuration proprietary configuration
Standard Dual-Pin Configuration
LT1112 first dual offered Linear Technology with standard configuration (Figure i.e., locations identical plastic CERDIP packages. Note that industry-standard package called package. order this package type, part number, illustrated Figure
Table Guaranteed matching specifications low-cost grades, ±15V, 25°C
Matching Specifications
addition outstanding specs Table LT1112 LT1114 also provide full matching specifications, facilitating their such matching-dependent applications three instrumentation amplifiers (Table performance these instrumentation amplifiers will limited matching parameters only-not specifications individual amplifiers (Figure
Parameter Typical Min/Max Offset Voltage Match Drift with Temperature Plastic/CERDIP SO-8 Non-Inverting Bias Current Match Common-Mode Rejection Match Power-Supply Rejection Match
Units µV/°C µV/°C
Parameter Typical Min/Max Units Offset Voltage Drift with Temperature Plastic/CERDIP 0.75 µV/°C SO-8 µV/°C Offset Current Bias Current Noise 10Hz 0.32 µVP-P 1kHz nV/Hz Supply Current/Amp Gain 5000 V/mV CMRR
Table Specifications low-cost grades with ±1.0V supplies, 25°C
Parameter
Typical Min/Max
Units µV/°C µV/°C
Guaranteed Specs ±1.0V Supplies
Another specifications furnished supplies. This, combined with 320µA supply current amplifier, allows
Offset Voltage Drift with Temperature Plastic/CERDIP 0.25 SO-8 0.45 Supply Current/Amp Common-Mode Range +250, -320 Swing (Light Load) ±270
Linear Technology Magazine October 1992
DESIGN INFORMATION
+1.5V
INPUT
LT1112 LT1114
0.5% 2.1k 0.5% 9.88k 0.5% 33pF
0.5%
(OPTIONAL)
LT1112 +0.617V
LT1097 LT1114
LT1004-1.2
OUTPUT
100pF
0.1%
GAIN 1000 TYPICAL PERFORMANCE INSTRUMENTATION AMPLIFIER: INPUT OFFSET VOLTAGE 40µV OFFSET VOLTAGE DRIFT 0.3µV/°C INPUT BIAS CURRENT 80pA INPUT OFFSET CURRENT 100pA INPUT RESISTANCE 800G INPUT NOISE 0.5µVP-P
1112_2.eps
LT1112 (OPTIONAL) -1.5V
INPUT
LT1112 LT1114
0.1% 0.617V
TRIM GAIN TRIM COMMON MODE REJECTION TRIM COMMON MODE REJECTION
TOTAL SUPPLY CURRENT 700µA. WORKS WITH BATTERIES DISCHARGED ±1.3V. ±1.5V: MAXIMUM LOAD CURRENT 800µA; INCREASED WITH OPTIONAL LOAD CURRENT 2mA. TEMPERATURE COEFFICIENT LIMITED REFERENCE 20ppm/°C.
1112_4.eps
Figure Three instrumentation with gain
Figure Dual-output reference operates cells
LT1112/LT1114 powered nearly discharged cells (Table dual-output, buffered reference application shown Figure
LTC1196/1198, continued from page
Figure works batteries, which discharged ±1.3V. With equal resistors, equal opposite-sign reference voltages
available. Changing ratio 0.1% resistors allows other values: positive negative.
Digital Considerations
reference input driven with standard voltage references. Bypassing reference with least 0.1µF recommended keep high-frequency impedance low. Some references require small resistor series with bypass frequency stability. individual reference data sheets details. achieve full sampling rate, analog input should driven with low-impedance source (<100) high-speed (e.g., LT1223, LT1191, LT1226). Higher-impedance sources slower amps easily accommodated allowing more time between conversions analog input settle. LTC1196/1198 will interface three four wires ASICs, PLDs, microprocessors, DSPs, shift registers. fastest conversion rate (600ns) must clocked 14.3MHz. logic families high speed ASIC will easily interface that speed. Connection microprocessor serial port very easy. requires additional hardware, speed will limited clock rate microprocessor DSP. TMS320 family's 7MHz serial-port clock rate fastest available present time. This limits conversion time LTC1196/1198 about 1µs. Fullspeed operation still achieved with ASICs, PLDs logic circuits. Check clock frequency timing specifications your particular ASIC PLD.
CONCLUSION
LTC1196 LTC1198 must considered alternative half-flash ADCs high-speed data acquisition systems because their high conversion speeds, small size, cost, power consumption, their ability operate both power supplies.
EFFECTIVE NUMBER BITS, ENOBs 100k
1196_5.
fSAMPLE 450kHz fSAMPLE 1.2MHz
INPUT FREQUENCY, (Hz)
Figure LTC1196/1198 ENOBs input frequency
Linear Technology Magazine October 1992
DESIGN INFORMATION
LTC1157 Dual 3.3V Micropower MOSFET Driver
3.3V-powered MOSFET driver available. LTC1157 dual micropower MOSFET driver makes possible switch either supply- ground-referenced loads through RDS(ON), N-channel switch. N-channel switches required 3.3V because P-channel MOSFETs have guaranteed RDS(ON) with 3.3V. LTC1157's internal charge pump boosts gate-drive voltage 5.4V above positive rail (8.7V above ground), fully enhancing logic-level, N-channel MOSFET 3.3V highside switching applications.
DRAIN-TO-SOURCE RESISTANCE
Skovmand
LTC1157 SUPPLY VOLTAGE 3.0V, 3.3V, 3.6V
voltage drive logic-level, high-side N-channel switch into full enhancement. This combination RDS(ON) MOSFET switch micropower gate drive produces maximum switch efficiency 3.3V high-side switch applications.
Typical Applications
Figure illustrates surface-mount MOSFETs LTC1157 (also available 8-pin packaging) used switch 3.3V loads. gate rise fall times typically tens microseconds, slowed adding resistors capacitor, shown second channel. Slower rise fall times sometimes required reduce start-up current demands large supply capacitors, which might otherwise glitch main supply.
0.01 GATE-TO-SOURCE VOLTAGE
1157_2.eps
Figure RDS(ON) typical logic level, N-channel MOSFET switch
On-Chip Charge Pump
charge pump completely onchip therefore requires external components generate higher gate voltage. Figure graph gate voltage above supply versus supply voltage. charge pump been designed very efficient, requiring only microamps standby mode microamps while delivering 8.7V power MOSFET gate. This makes LTC1157 particularly well suited battery-powered applications, which benefit from micropower operation.
Logic Level MOSFET Switches
Figure graph RDS(ON) versus typical logic-level, N-channel MOSFET switch. RDS(ON) drops dramatically gate voltage taken above threshold voltage (1-2V) begins flatten about 3.5V. Further gate drive does significantly reduce RDS(ON), because MOSFET channel already fully enhanced. mapping LTC1157 supply voltage onto Figure seen that on-chip charge pump produces ample gate
3.3V
10µF
VGATE
CONTROL LOGIC LTC1157
IRLR024 3.3V LOAD 100k IRLR024 0.1µF 3.3V LOAD
1157_1.eps
LARGE SUPPLY CAPACITOR
1157_3.eps
SUPPLY VOLTAGE
Figure LTC1157 used switch 3.3V loads
Figure Gate voltage above supply supply voltage
Linear Technology Magazine October 1992
DESIGN INFORMATION
World's Lowest-Noise Available 8-pin Unity-Gain Stable Version George Erdi
Alexander Strong
LT1128
1028_2.eps
Figure Driving heavy capacitive load
LT1028 introduced 1986. With 0.85nV/Hz noise (less than that resistor) became lowest voltage-noise amp, wresting title from LT1007, which features noise 2.5nV/Hz. LT1028 combined minuscule noise with excellent precision high-speed specifications (Table years later, LT1028 still reigning low-noise champion. addition, LT1028 available 8-pin small-outline surfacemount package-designated LT1028CS8. many amps, assembly shifts surface-mount packages necessitate loosening specifications compared other packages. LT1028CS8, spec
relaxation necessary. designation indicates that LT1028CS8's specifications identical LT1028CH, LT1028CJ8, LT1028CN8. LT1028 stable closed-loop gains voltage follower. first glance, this should never problem, since proper LT1028 always involves amplification microvolt-level signals take advantage noise. However, optimize noise, bandwidth amplifier should limited bandwidth signal being processed. many applications, only convenient means limiting bandwidth connect capacitor (CF) parallel with feedback resistor. high frequencies this capacitor becomes short, requiring unity-gain-stable amplifier.
Enter LT1128
LT1028 stable many combinations LT1128, however, unconditionally stable values Another example which requires unity-gain stability shown
Figure Here, heavy capacitive load, isolated from amp's output resistor extra phase shift caused pole eliminated from consideration presence which shorts amp's output input high frequencies. instrumentation amplifiers usually have amps with fixed gain greater than input stage (Figure frequencies, decompensated amps work well, high frequencies with input grounded, virtual ground begins lose integrity. frequency input signal increases, amplitude virtual ground increases, making virtual ground look inductive, eventually requiring unitygain-stable amplifier. LT1028 made stable under these conditions with bypass capacitors little experimenting, LT1128 unconditionally stable. LT1028/LT1128 team offers user excellent performance, unconditional stability, lowest noise available amp. these features available surface mount package.
Table LT1028/LT1128 Comparison
LT1028A/ LT1028C/ 1128A 1128C TCVOS 0.85 11.0 ±180 11.0
LT1128
Units µV/°C nV/Hz nV/Hz nV/Hz V/µV V/µs V/µs
LT1037
SIGNAL INCREASES WITH FREQUENCY THIS NODE
GAIN 1000
AVOL
10kHz 1kHz 1kHz (100% tested) 1028 1128 1028 20kHz 1128 200kHz
LT1128
INPUT REFERRED NOISE 1.5nV/Hz 1kHz WIDE BAND NOISE 1.4µVRMS BAND LIMITED 100kHz 0.6µVRMS GAIN BANDWIDTH PRODUCT 400MHz
1028_3.eps
Figure Three amp, ultra-low noise instrumentation amplifier
Linear Technology Magazine October 1992
DESIGN IDEAS
Temperature-Compensated, Voltage-Controlled-Gain Amplifier Using LT1228 Frank
often convenient control gain video intermediate frequency (IF) circuit with voltage. LT1228, along with suitable voltageto-current converter circuit, forms versatile gain-control building block ideal many these applications. addition gain control over video bandwidths, this circuit differential input sufficient output drive systems. transconductance LT1228 inversely proportional absolute temperature rate 0.33%/°C. circuits using closedloop gain control (i.e., video automatic gain control) this temperature coefficient does present problem. However, open-loop gain-control circuits that require accurate gains require some compensation. circuit described here uses simple thermistor network voltage-tocurrent converter achieve this compensation. Table summarizes circuit's performance.
Table Characteristics example
+15V 4.7µF 10.7k
10.7k
ROUT RLOAD
-15V
VCON
Figure Differential-input, variable-gain amplifier
GAIN
ERROR
GAIN
Input Signal Range 0.5V 3.0V Desired Output Voltage 1.0V Frequency Range 5MHz Operating Temperature Range 50°C Supply Voltages ±15V Output Load Control Voltage Gain Relationship Gain Gain Variation Over Temperature from Gain 25°C
GAIN -12.5 12.5 37.5 TEMPERATURE (°C)
1228_5.
62.5
Figure Gain error circuit Figure plus temperature compensation circuit shown Figure (normalized gain 25°C)
Figure shows complete schematic gain-control amplifier. Please note that these component choices only ones that will work they necessarily best. This circuit intended demonstrate approach many this very versatile part and, always, designer's engineering judgment must
Linear Technology Magazine October 1992
fully engaged. Selection values input attenuator, gain-set resistor, current-feedbackamplifier resistors relatively straightforward, although some iteration usually necessary. best bandwidth, remember keep gain-set resistor, small possible, current large possible
4.7µF
ISET
82.5
1228_1.
(with regard gain compression). voltage-controlled current source (ISET) detailed boxed section. Several these circuits have been built tested using various gain options different thermistor values. Test results these circuits shown Figure gain error versus temperature this circuit well within limit ±3%. Compensation over much wider range temperatures tighter tolerances possible, would generally require more sophisticated methods, such multiple thermistor networks. VCCS standard circuit with exception current-set resistor which made have temperature coefficient -0.33%/°C. sets overall gain made adjustable trim initial tolerance LT1228 gain characteristic. resistor (RP) parallel with thermistor will tend, over relatively small range, linearize change resistance combination with temperature. trims temperature coefficient network desired value.
DESIGN IDEAS
Voltage-Controlled Current Source (VCCS) with Compensating Temperature Coefficient
266k 2.2k3A1 50pF 1780 LT1006 2N3906 ISET ISET (MIN) ISET VoHoge
1228_2.
ISET (MAX)
2.26M VCON
4320
150k
ISET
VCON
1228_4.
Figure Voltage-controlled current source (VCCS) with compensating temperature coefficient
Figure Voltage control ISET with temperature compensation
VCCS Design Steps
Measure obtain from data sheet thermistor resistance three equally spaced temperatures this case 0°C, 25°C, 50°C). Find from:
R50) R25)
(temp. RP||RT) )-(R (0.33) contributes resultant temp made large with respect other resistors calculated give desired range ISET. This procedure performed using variety thermistors (one possible source BetaTHERM corporation-phone 508-842-0516). Figure shows typical results reported errors normalized resistance with -0.33%/°C temperature coefficient. practical matter, thermistor need only have about tolerance this gain accuracy. sensitivity gain accuracy thermistor tolerance decreased linearization network, same ratio temperature coefficient; room temperature gain trimmed with course, particular applications require analysis aging stability, interchangeability, package style, cost, contributions tolerances other components circuit.
RESISTANCE
THERMISTOR COMPENSATED NETWORK
where thermistor resistance thermistor resistance 25°C thermistor resistance 50°C Resistor placed parallel with thermistor. This network temperature dependence that approximately linear over range given (0°C-50°C). parallel combination thermistor (RP||RT) temperature coefficient resistance (temp. co.) given
R0||RP R50||RP temp. RP||RT R25||RP
TEMPERATURE (°C)
1228_3a.
Figure Thermistor thermistor network resistance temperature
ERROR
THIGH TLOW
where THIGH high temperature TLOW temperature thermistor desired temp. compensate LT1228 gain temperature dependence -0.33%/°C. series resistance (RS) added parallel network trim temp. proper value. given
TEMPERATURE (°C)
1228_3b.
Figure Thermistor-network resistance normalized resistor with exact -0.33%/°C temp.
Linear Technology Magazine October 1992
DESIGN IDEAS
Flash-Memory Generator Shuts Down with Output
Nonvolatile "flash" memories require well-controlled bias (VPP) programming. tolerance memories. Excursions above below -0.3V destructive. often generated with boost regulator whose output follows input supply when shut down. sometimes desirable force when memory read-only mode. circuit Figure generates smoothly rising 12V, 60mA supply that drops under logic control. Shortly after driving SHUTDOWN high, LT1109-12 switching regulator drives producing high-voltage pulses device's switch (Figure 1N5818 Schottky diode rectifies these pulses charges reservoir capacitor functions low-on-resistance pass element. 1N4148 diode clamps reverse voltage protection. circuit does overshoot display unruly dynamics, because regulator gets feedback directly from output Q1's collector. Minor slew aberrations Q1's switching characteristics.
Sean Gold
Even with additional losses introduced efficiency with 60mA load. Line load regulation both less than Output ripple about 100mV under light loads. Quiescent current drops 400µA when shut down. components shown Figure available surface mount packages, making circuit well suited flash memory cards other applications where minimizing pc-board space critical.
1N4148 33µH 22µF LT1109A-12 SHUTDOWN SENSE SHUTDOWN PROGRAM
1109a_1.eps
1N5818
SHUTDOWN 5V/DIV
22µF 2N4403 60mA
5V/DIV
Figure Boost-mode switching regulator with R-on pass transistor flash-memory programming
Figure Input output waveforms flash-memory programming circuit
Bias Supply
requires bias supply contrast control. supply's variable negative output permits adjustment display contrast. Relatively little power involved, easing radiation efficiency requirements. bias generator shown Figure this circuit, LT1173 micropower DC-to-DC converter. input converted +24V U1's switch, switch (SW1) also drives charge pump composed generate -24V. Line regulation less than 0.2% from 3.3V inputs. Although load regulation suffers somewhat because -24V output directly regulated, measures loads from 7mA. circuit will deliver from input efficiency.
ILIM
Steve Pietkiewicz
100µH 1N5818 OUTPUT +12V +24V
LT1173
2.21M
4.7µF
0.1µF 100k
1N5818 1N5818 1N4148
CELL
120k
OPERATE SHUTDOWN TOKO 262LYF-0092K
22µF OUTPUT -12V
1173_1.eps
Figure Converter Generates Bias
Linear Technology Magazine October 1992
DEVICE CAMEOS
Device Cameos
LT1201/LT1202: High-Speed, Low-Power, Dual Quad Operational Amplifiers
LT1201 dual version LT1200 high-speed, low-power operational amplifier; LT1202 quad version. Each unity-gain-stable amplifier 11MHz gain bandwidth, 50V/µs slew rate, 430ns settling time 0.1% (10V step), draws only quiescent supply current. LT1201/1202 ideal choices applications where power consumption board space must minimized. With maximum offset voltage, 100nA maximum offset current, 8V/mV open-loop gain combined with fast settling, LT1201/ 1202 excellent choices fast data-acquisition systems. Each amplifier drive load ±12V from ±15V supply drive supplies. amplifiers stable with capacitive loads, which makes them useful buffers driving A-to-D converters. Wideband active filters another excellent application, especially where power consumption critical battery operation. LT1201 comes industrystandard pinout 8-lead plastic mini-DIP 8-lead, small-outline surface-mount package. LT1202 comes 14-lead plastic DIP. 7V/mV open-loop gain. outputs drive load ±12V with ±15V supply drive supply. amplifiers stable with capacitive loads, which makes them useful buffers cable-driving applications. excellent settling time lends itself data-acquisition applications, such current-to-voltage converters A-to-D input buffers. Other applications include wide-band active filters, amplification, video amplifiers. LT1208 comes industrystandard pinout 8-lead plastic mini-DIP 8-lead small-outline surface-mount package. LT1209 comes 14-lead plastic DIP.
LTC1154 High-Side, Microprocessor-Compatible, Micropower MOSFET Driver
LTC1154 single micropower gate driver designed drive standard N-channel power MOSFET highside switch configuration. LTC1154 contains on-chip charge pump that less expensive, lower RDS(ON) Nchannel MOSFETs used place P-channel switches. charge pump requires external components been designed very efficient, requiring only microamps operate. circuitry drive, control, protect power MOSFET load, interface host microprocessor, provided LTC1154. input compatible with both CMOS logic families standby current with input switched only microamps from supply. quiescent current rises microamps when switch turned charge pump producing from supply. active-low enable input provided control multiple LTC1154 switches banks. open-drain status output provided advise microprocessor when fault condition exists output switch. over-current condition detected drain power MOSFET, output latched status pulled low. built-in 10-microsecond delay ensures that LTC1154 protection circuitry false triggered transient load power-supply conditions. longer delay added externally accommodate loads with large transient start-up current requirements, such lamps motors. versatile microprocessor interface, coupled with comprehensive protection features micropower operation, make LTC1154 ideal choice applications that require maximum efficiency protection lean power budget. 8-lead packaging makes ideal choice applications with lean boardspace budget.
Linear Technology Magazine October 1992
LTC1250 Very-Low-Noise Bridge
LTC1250 zero-drift optimized with bridge transducers. features typical 0.1Hz-10Hz noise 0.65µVP-P 0.1Hz-1Hz noise 0.2µVP-P, making ideal with noise, frequency signals. LTC1250's 10µV maximum offset, 50nV/°C maximum drift, ±150pA maximum bias currents keep errors negligible. zero-drift loop samples input 5kHz, allowing signals 2.5kHz amplified with aliasing. zero-drift circuitry integrated on-chip, allowing LTC1250 plug into standard op-amp sockets with additional external components. LTC1250 enhanced CMOS output stage capable swinging into with supplies; will swing within millivolts rail into lighter loads. 10V/µs slew rate 1.5MHz gain bandwidth allow LTC1250 track input transients. inputs recover from overload 1.5ms, many times faster than standard zero-drift amps with external capacitors. LTC1250 ideally suited electronic scales, pressure transducers, low-frequency digitizing applications.
LT1208/LT1209: 50MHz, 400V/µs Dual Quad Operational Amplifiers
LT1208 dual version LT1224 high-speed operational amplifier; LT1209 quad version. Each amplifier unity-gain stable with 50MHz gain bandwidth, 400V/µs slew rate, 90ns settling time 0.1% (10V step), supply current. LT1208 LT1209 ideal choices applications where high speed essential board space must minimized. LT1208/1209 specifications include maximum offset voltage, 400nA maximum offset current,
DEVICE CAMEOS
LT1269: 100kHz, Highregulators buck mode, while using portable instruments computers. Efficiency Switching Regulator LT1432-3.3 feedback signal dimly environments some form
integrated switching regulator LT1269, allows highefficiency converters constructed using smaller inductors than were required with previous devices. Similar LT1271 other members LTC's 5-pin integrated switching-regulator family, LT1269 contains 100kHz current-mode control section, fully integrated high-efficiency switch, fault protection single chip. operated standard switching configurations, including buck (stepdown), boost (step-up), flyback, inverting, others. Used with companion control chip, LT1432, LT1269 used make very-high-efficiency stepdown regulator with typical NiCad Nickel-Hydride battery packs used portable computers. addition providing high efficiency 90%) load currents beyond, device, when used with LT1432, accomplishes difficult task maintaining high efficiency under power-demand conditions. Such conditions encountered portable computers when power-management schemes such "suspend-mode" employed. 3.3V version LT1432 that allows LT1269 used generate 3.3V logic supplies with high efficiency available (see below). LT1269 comes 5-lead TO-220 5-lead surface-mount package planned future release. conditioning. Portable, battery-powered systems achieve significant power savings increased battery life using idle "suspend" mode when system actively use. Notebook computers typically employ such power-saving scheme. suspend mode, when output load demand light, LT1432-3.3 place main regulator into "burst" mode maintain high efficiency load currents 50mA). logic-compatible shutdown included that, when taken high, shuts entire regulator down. LT1432-3.3 offered 8-lead SOIC package 8-pin mini-DIP. backlighting required make panel readable. preferred light source cold-cathode fluorescent lamp, otherwise known "CCFL." CCFLs relatively efficient light sources, they require special power supplies develop high starting running voltages 1kV). AN49 explains nature CCFL load, tells design suitable power supply. circuits described AN49 preserve overall efficiency CCFL extend battery life portable systems eliminate "hot spots" inside product. AN51: Power Conditioning Notebook Palmtop Systems Notebook palmtop systems need multiplicity regulated voltages developed from single battery. Small size, light weight, high efficiency mandatory competitive solutions this area. Small increases efficiency extend battery life, making final product much more usable with increase weight. Additionally, high efficiency minimizes heat sinks needed power-regulating components, further reducing system weight size. AN51 presents collection twenty circuits that represent state-of-the-art solutions power-supply problems portable computing products. These circuits were designed high efficiency small size, cover every requirement from battery charging LCD-bias generation. further information above other devices mentioned this issue Linear Technology, reader service card call literatureservice number: (800) 637-5545. pertinent data sheets application notes.
Information furnished Linear Technology Corporation believed accurate reliable. However, responsibility assumed use. Linear Technology makes representation that circuits described herein will infringe existing patent rights.
LT1129: 700mA Low-Iq, Low-Dropout Regulator
LT1129 low-dropout regulator with ultra-low quiescent current shutdown current. device supply over 700mA output current with dropout voltage 0.4V maximum output. 50µA quiescent current operating mode 30µA shutdown mode perfect battery powered operation. This quiescent current does rise dropout region does with other low-dropout regulators. Other features LT1129 include ability operate with small output capacitors. Stability guaranteed with only 3.3µF output capacitance, whereas other low-dropout regulators require much 100µF. input LT1129 connected ground, reverse input voltages applied without current flow from output input. This makes LT1129 ideal back-up power applications where output held high while input ground. device available 5-lead TO220 surface mount packages.
LT1432: High-Efficiency, Step-Down SwitchingRegulator Controller
LT1432-3.3 8-pin control chip designed work conjunction with LTC's family 5-pin integrated switching regulators make very-high-efficiency 3.3V switching regulators with advanced power-management capability. High efficiency nominal output currents from 0.1A over achieved employing LTC's LT1070 family low-loss switching
Linear Technology Magazine October 1992
Publications
AN49: Illumination Circuitry Liquid Crystal Displays (Tripping Light Fantastic.) Liquid crystal displays have become almost universal
DESIGN TOOLS
Applications Disk
NOISE DISK This IBM-PC compatible) progam allows user calculate circuit noise using amps, determine best noise application, display noise data amps, calculate resistor noise, calculate noise using specs amp. Available charge. SPICE MACROMODEL DISK This IBM-PC compatible) high density diskette contains library SPICE macromodels. models used with version SPICE general analog circuit simulations. diskette also contains working circuit examples using models, demonstration copy PSPICEby MicroSim. Available charge.
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Technical Books
1990 Linear Databook This 1,440 page collection data sheets covers amps, voltage regulators, references, comparators, filters, PWMs, data conversion interface products (bipolar CMOS), both commercial military grades. catalog features well over devices. $10.00 1992 Linear Databook Supplement This 1248 page supplement 1990 Linear Databook collection products introduced since then. catalog contains full data sheets over devices. 1992 Linear Databook Supplement companion 1990 Linear Databook which should discarded. $10.00 Linear Applications Handbook pages full application ideas covered depth Application Notes Design Notes. This catalog covers broad range "real world" linear circuitry. addition detailed, systemsoriented circuits, this handbook contains broad tutorial content together with liberal schematics scope photography. special feature this edition includes 22page section SPICE macromodels. $20.00 Monolithic Filter Handbook This page book comes with disk which runs PCs. Together, book disk assist selection, design implementation right switched capacitor filter circuit. disk contains standard filter responses well custom mode. handbook contains over data sheets, Design Notes Application Notes. $40.00 SwitcherCAD Handbook This page manual, including disk, guides user through SwitcherCAD powerful software tool which aids design optimization switching regulators. program days design cycle selecting topologies, calculating operating points specifying component values manufacturer's part numbers. $20.00
LINEAR TECHNOLOGY CORPORATION
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1992 Linear Technology Corporation/ Printed U.S.A./20K
Linear Technology Magazine October 1992
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