Ivan Duzevik National Semiconductor, South Portland, Maine Abstract Th
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Preliminary Results Passive Component Measurement Methods Using IEEE 1149.4 Compliant Device
Ivan Duzevik National Semiconductor, South Portland, Maine Abstract This paper demonstrates several methods measurement passive components using IEEE 1149.4 compliant device cost laboratory measurement equipment. will briefly describe IEEE 1149.4 mixed signal test standard features, will describe device that used prove concepts virtual probing, measurements data acquisition possibilities. order demonstrate these capabilities quantities were measured: resistance, capacitive impedance. unknown resistor values calculated simple Ohm's equations, unknown capacitance calculated using methods: roll-off point method method. real-time nature analog measurements demands search fast simple measurement techniques. Common passive components were chosen these measurements, cost instrumentation (voltmeters function generators) used emphasize capabilities IEEE 1149.4 standard. methods described full results presented end. Introduction Printed circuit boards assemblies increasingly difficult test; therefore test technologies such boundary -scan have emerged tackle these problems. IEEE 1149.1 become prevalent solution board debug, manufacturing test, remote test diagnostics. standard very successful with digital devices; however, analog mixed signal testing left IEEE 1149.4 Standard. IEEE 1149.4 Standard, "dot constructed superset IEEE 1149.1 Std. objective offer solutions testing analog signals components environments that suffering from high congestion devices, board layers, remote shielded access. other words, provides possibility probing node voltages data acquisition unknown expected values passive components. standards very similar, both include (Test Access Port) controller, mandatory 1149.1 instructions apply well, they both include optional user defined instruction sets. features following: -Analog test pins have four-bit analog boundary module (ABM), bits 1149.1 control, control analog switches. -Dot devices have internal analog buses (AB1 AB2), which connected external (on-board) analog buses (AT1 AT2) respectively. typically used stimulus (current drive path), typically used voltage sense path (measurement). -The internal external analog buses connected through Test Interface Circuit (TBIC) switches. -PROBE instruction used real time voltage monitoring while device mission circuit active. There have been several test demo chips designed over years. used this paper National Semiconductor /LogicVision SCANSTA400. SCANSTA400 Description SCANSTA400 20-pin device; IEEE 1149.1 pins (TCK, TDI, TDO, TMS, TRST*), analog test pins (AT1 AT2), mission circuit control pins (CE, CEI, Mode, C0), analog multiplexer pins (A0, A01, A23) (Figure used monitoring analog signals, well assisting measurement passive components. mission circuit contains analog multiplexers, which configured SCANSTA400 fully 1149.1 1149.4 compliant, supports HIGHZ CLAMP instructions. truth table setting mission mode circuit
operation given (Table CEI, Mode pins also pins. When chip analog test mode, those used pins. This makes device capable reaching total eleven (11) nodes measurement monitoring.
stimulus source node under test established through SCANSTA400. used measurement path. closing TBIC switches switch interest, path established through inside chip node interest. This high impedance path, voltage measurement considered node". other words, serves voltmeter probe measured node. resistor being measured, terminals connected pins. resistance calculated subtracting terminal voltages from each other dividing result current stimulus value. conclude, attaching stimulus source AT1, measurement instrument AT2, while using SCANSTA400 geometry switch, voltages observed passive component values between nodes calculated. Resistor measurements this case resistor ground measured. Three values were used current stimulus: 100, analog switch configuration measurement setup presented Figure
Fig. SCANSTA400 block diagram
Mode connected connected connected connected connected connected
TBIC switches
equal
Switches
measured
equal
Voltmeter STA400
Table SCANSTA400 Truth Table switch configuration function ABM's TBIC fully controlled user 1149.1 capabilities. Serial vector format (SVF) been used vector delivery format experiments presented this paper. Please refer manufacturer BSDL file datasheet SCANSTA400. measurements Analog voltage probing core measurement capability this device IEEE 1149.4 standard. pin, connected internal bus, used current stimulus path. path switched through TBIC switches desired pin. switch that particular turned therefore current path between Figure Measurement setup switch configuration simplified internal switch structure SCANSTA400 represented inside dotted line, where AT1, three SCANSTA400's pins. switches IEEE 1149.1-controlled SCANSTA400 PROBE instruction mode. Figure shows equivalent circuit which switch resistances taken into consideration. measurement path high impedance path. unknown resistance calculated using formula:
Vnode Istimulus
TBIC
NODE
measured
stimulus
Voltmeter
Figure Equivalent circuit Results from resistor measurements Three values were used stimulus: 100, 500uA. Before measurements, current source calibrated using high precision 1Kohm resistor. current values were then used calculate unknown resistors. Full results three different current values represented Table paper. unknown resistors were measured with HP3478A voltmeter results were considered nominal values. last column value obtained measuring resistors with conventional HP3478A voltmeter. first, third fifth columns contain values measured with SCANSTA400. arithmetic difference between IEEE 1149.4 measured values nominal values were then divided nominal value multiplied 100%, which represents error percentage measurement setup. Second, fourth sixth columns show resistance measurement error values respective current stimulus values. accuracy illustrated Figure graph shows areas values that were measured within nominal value, areas where current source compliance right area), instrument resolution left area), allow better accuracy.
Source compliance
understand range accuracy this method. current source operates 3.3V power supply; needs precision resistor parallel desired current, also needs minimum 0.9V drop within desired accuracy. Therefore, maximum voltage that current source supply 2.4V, which means that resistor values that exceed
Iset measured with this setup. other hand, very resistor values were measured because limit resolution HP3478A digital voltmeter. Only measured voltage values greater than 0.001V were trusted this experiment. measuring wider range resistor values recommended high precision measurement device high precision current source. switch setup remains same.
case resistor between nodes network, same measurement performed using pins SCANSTA400 device (Figure node voltages measured resistor value will obtained from following equation
Istimulus
NODE (V1)
stimulus
measured NODE (V2)
STA400
Vmeas
Source compliance
Resistance (ohms)
Vmeas
Source
Figure Resistor network Another possible method resistor measurement resistor network following: Rather than probing actual node voltage second terminal resistor, virtual ground introduced that node using EXTEST instruction (Figure virtual ground sinks current from stimulus, through measured resistor. terms digital operation, this controlled using
2.4K
100K 19.9K 259K
Figure Accuracy Discussion resistor measurements current source LM334 from National Semiconductor used stimulus. Several constraints must examined order better
IEEE 1149.1 compliance ABM's. logic zero driven used current sink. voltage connected second node still needs measured AT2, however virtual ground value approximately 0.2V. This important cases where second terminal's voltage drop higher than desired cause problems with compliance functionality.
stimulus
Voltmeter
Figure Additional measurement would have done determine phase measured voltage (given phase current known from source). With those values, nature impedance obtained (capacitive inductive). real world applications high precision instruments expensive always available. This paper will discuss cases where accurate sophisticated instruments used measurement setup. test community's objective researching capability IEEE 1149.4 further simplify process testing, lower cost, provide alternative ways probing values remote circuits shielded areas. Therefore, important assumption must considered before next paragraphs, that Only off-theshelf equipment that found moderately equipped laboratories used following measurement experiments. Instrumentation includes: digital voltmeter, function generator, oscilloscope (although oscilloscope required). second assumption that expected values capacitive, passives that measured this paper common capacitor values. Roll-off point method This method requires tunable function generator digital voltmeter. setup shown Figure pass filter circuit formed with internal SCANSTA400 TBIC switch resistance external unknown capacitor.
TBIC
virtual STA400
measured
Figure Sinking current from second terminal Rmeasured measurements Methods approach Having accomplished successful resistor measurements using stimulus measurement device, next challenge determine method impedance measurements using IEEE 1149.4. find impedance device necessary measure least values because edance complex quantity. methodology impedance measurement field study own. There many instruments capable measuring real imaginary parts impedance, phase absolute value. However when IEEE 1149.4 considered challenge find relatively inexpensive fast method utilizing analog buses, AT2. theory, high precision current source will provide stimulus through AT1, accurate voltmeter would measure voltage drop across unknown impedance through (Figure providing values Ohm's equation:
Function generator
Voltmeter
Figure circuit formed from internal resistances measured Capacitor
roll-off -3dB) frequency filter found tuning input frequency monitoring output value. input frequency comes from function generator voltage output measured bus. IEEE 1149.4 implementation shown Figure unknown capacitance calculated
Method absence high precision current source, sinusoidal voltage function used stimulus determine current flowing through series impedances where components known value. voltages terminals impedances measured using IEEE 1149.4 device; therefore three values (current voltage) obtained find final -the impedance. this paper, impedances capacitors were measured, therefore phase angle assumed degrees (ideal capacitor). Figure shows equivalent schematic figure shows SCANSTA400 switch setup.
Function generator
TBIC switches
Switches
STA400 Voltmeter
Figure IEEE 1149.4 implementation circuit from figure Results Discussion
Within Accuracy Measured Value 1000 10000 100000 1000000 1E+07 (pF)
Function generator
Voltmeter
Figure method voltage function generator, following complex (Figure 11a) diagram drawn:
Figure Roll-off method accuracy Figure shows obtained accuracy function capacitor values measured. accuracy deteriorates measured capacitance decreases. This fact that SCANSTA400 itself parasitic capacitance, which combined with stray capacitance measurement environment (PCB board this case) results value order tens Pico farads. This underlines need calibration IEEE 1149.4 device measurement environment. stray capacitance calculated, characterized, known prior tests, accuracy will significantly improved.
Figure 11a. Complex diagram Where voltages across resistor capacitor, respectively. This IEEE 1149.4 setup allows measure complex values Vfg; therefore assuming true capacitor with degrees, calculate using:
(Vfg
Knowing value allows calculate capacitor value using following equations:
Where
capacitor's value, circuit must specific frequency range capacitor have impact circuit. Namely, circuit pass filter, which means that frequencies below above roll-off (-3dB) region output voltage either equal input voltage (Va1=Va23) zero, regions figure respectively. Therefore, value must frequency region (0.2f-3dB 20f-3dB). Correct measurements accurate results dependent three variables: known resistor value, frequency measurement, expected capacitor value. illustration relationship between three values given Figure where expected capacitance value
IEEE 1149.4 implementation shown Figure
Switches
Function generator
Vout (dB)
TBIC switches
Switches
Voltmeter
1000 10000 100000 1000000
frequency
STA400
Figure Frequency response example filter.
Resistor value (ohms)
0.00001 0.000001 1000 10000 100000 1000000
Figure IEEE 1149.4 implementation method this case, equations rewritten represent actual circuit. voltage becomes vector difference between voltage measured voltage measured pin, VA23 respectively. voltage becomes VA23 equation voltage becomes therefore calculated following expression:
Capacitance
1E-07 1E-08 1E-09 1E-10 1E-11 1E-12
Figure Relationship between different frequencies measurement that measured y-axis known resistor x-axis. When specific capacitor value expected, frequency resistor chosen directly from graph. However, figure shows that whole range (region from 0.2f-3dB 20f-3dB) frequencies could used same product. example, roll-off frequency circuit 1000 frequencies that used accurate measurements between 10,000
(VA1 VA23
VA23
Results Discussion frequency measurement inversely proportional product measured capacitance known resistor. bandwidth limitations IEEE 1149.4 device circuit board, frequency must chosen carefully. order calculate
Table shows results obtained with method. total parasitic capacitance open-socket measurement setup order hundred Pico farads; which made measurement small capacitors difficult. compensate this parasitic, open-socket capacitance measurement performed every combination frequency resistance used. difference between open-socket capacitance value measured capacitor value presented final calculated capacitor value. simplification another possible version method should mentioned here well. very small resistor, order tens ohms, used method, possible avoid errors phase angle capacitive voltage That accomplished introducing small error equation assume that voltage phase with voltage, that degrees, relatively good measurement accuracy achieved. This having known resistor very value compared total impedance capacitor resistor series. Because expect passive (discrete) capacitor with unknown expected) value, this assumption helps determine capacitor value very elegant way. Conclusion order measure resistors capacitors circuit board, their values must expected prior tests. "force sense" methods require familiarity with system under test. case resistor measurements current stimulus value must optimized actual board IEEE 1149.4 device. capacitor measurement, external resistor frequency measurement influence accuracy reliability results, therefore must carefully calculated taking characteristics environment into consideration. methods this paper just many possibilities that IEEE 1149.4 Standard SCANSTA400 device offer passive component measurement. results presented this paper order accuracy resistors capacitors. measurements were performed using common digital voltmeter (HP3478A) common function generator (HP8116A). accuracy will significantly improve with
more expensive instrumentation, however goal this research demonstrate capability IEEE 1149.4 device measure passive components using inexpensive equipment. Although current absence automated test pattern generation (ATPG) tools IEEE 1149.4 Standard makes process creating vectors test patterns cumbersome prone errors, test community working overcome this obstacle. results this paper, other research efforts done this field, clearly show significance IEEE 1149.4 Standard, provide appropriate incentive continue "dot4" ATPG development efforts. SCANSTA400 proven concept voltage probing passive component measurement. versatility methods, results obtained, justify future efforts fill existing gaps automation implementation IEEE 1149.4. IEEE 1149.4 Standard promises solve analog test issues inexpensive highly reliable fashion. References IEEE Standard 1149.4-1999, "Standard Mixed Signal Test Bus", IEEE, USA, 2000. IEEE Standard 1149.1-2001, "Standard Test Access Port Boundary Scan Architecture", IEEE, USA, 2001 Sunter, Filliter, Woo, McHugh, General Purpose 1149.4 with Analog Test Capabilities", Proceedings IEEE International Test Conference, Oct. 2001. Analog Mixed-Signal Boundary Scan, Osseiran, Kluwer Academic, USA, 1998. Impedance Measurement Handbook, Agilent Technologies ww.agilent.com), USA, 2000.
Resistance measurement results
accuracy accuracy accuracy Value measured 500µA) 100µA) with HP3478A 5.66 -0.8 10.39 10.31 24.36 24.2 33.90 33.8 50.93 50.7 52.16 51.9 76.32 100.42 100.36 99.96 138.18 138.50 137.5 317.07 316.33 315.6 480.81 480.80 605.05 603.70 606.00 603.2 1003.23 1001.60 1000.00 999.8 2014.34 2010.00 2016.00 2008.3 2234.34 2233.00 2240.00 2230 2430.30 2432.00 2438.00 2430 3238.00 3245.00 3238 3563.00 3570.00 3562 6181.00 6186.00 6178 10004.00 10020.00 9990 19970.00 -0.1 20020.00 19981 26660.00 26644 30120.00 30084 30189.00 30175 62120.00 62123 75290.00 75220 100170.00 100041 Table Resistor measurement results
Column resistor value measured with current stimulus Column accuracy calculated with formula: 3478 value measured value) accuracy 3478 value Column current stimulus value Column current stimulus value Column value resistors measured with HP3478A voltmeter.
Capacitance measurement results
(Hz) 10000 20000 10000 80000 10000 10000 50000 20000 40000 10000 20000 50000 80000 1000 2000 5000 10000 20000 50000 1000 2000 1000 (ohms) 440000 440000 440000 440000 1000000 440000 440000 20000 20000 1150 1150 1150 1150 20000 20000 20000 20000 20000 20000 440000 440000 1000000 15.5 15.5 actual calculated accuracy capacitor value capacitor value 4.69 4.33 9.74 9.27 9.16 191.36 197.00 182.57 181.88 10.64 10.36 10.16 10.10 10.80 10.59 10.44 10.34 10.25 10.27 10.41 9.99 9.80 22.49 22.06 20.45 23.48
Table Capacitor measurement results
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