MAX6650 MAX6651
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Fan-Speed Regulators Monitors with SMBus/I2C-Compatible Interface
MAX6650/MAX6651 controllers SMBusTM/I2C*-compatible interface regulate monitor speed 5VDC/12VDC brushless fans with built-in tachometers. They automatically force fan's tachometer frequency (fan speed) match preprogrammed value Fan-Speed Register using external MOSFET bipolar transistor linearly regulate voltage across fan. MAX6650 regulates speed single monitoring tachometer output. MAX6651 also regulates speed single fan, contains additional tachometer inputs monitor four fans control them single unit when they used parallel. MAX6650/MAX6651 provide general-purpose input/output (GPIO) pins that serve digital inputs, digital outputs, various hardware interfaces. Capable sinking 10mA, these open-drain inputs/outputs drive LED. additional hardware control, configure GPIO1 fully turn case software failure. generate interrupt when fault condition detected, configure GPIO0 behave activelow alert output. Synchronize multiple devices setting GPIO2 (MAX6651 only) internal clock output external clock input. MAX6650 available space-saving 10-pin µMAX package, MAX6651 available small 16-pin QSOP package.
_Features
Closed/Open-Loop Fan-Speed Control 5V/12V Fans 2-Wire SMBus/I2C-Compatible Interface Monitors Tachometer Output Single Tachometer (MAX6650) Four Tachometers (MAX6651) Programmable Alert Output GPIOs Hardware Full-On Override Synchronize Multiple Fans Four Selectable Slave Addresses 5.5V Supply Voltage Small Packages 10-Pin µMAX (MAX6650) 16-Pin QSOP (MAX6651)
MAX6650/MAX6651
Ordering Information
PART MAX6650EUB TEMP RANGE -40°C +85°C PINPACKAGE µMAX QSOP CODE U10-2 E16-1
MAX6651EEE -40°C +85°C SMBus trademark Intel Corp.
_Applications
RAID Servers Workstations Desktop Computers Networking Telecommunications
*Purchase components from Maxim Integrated Products, Inc., sublicensed Associated Companies, conveys license under Philips Patent Rights these components system, provided that system conforms Standard Specification defined Philips. Configurations appear data sheet.
Typical Operating Circuit
VFAN 5.5V
MAX6650
SMBus/I2C INTERFACE TACH0
ALERT FULL GPIO0 GPIO1 CCOMP 10µF
Maxim Integrated Products
pricing, delivery, ordering information, please contact Maxim/Dallas Direct! 1-888-629-4642, visit Maxim's website www.maxim-ic.com.
Fan-Speed Regulators Monitors with SMBus/I2C-Compatible Interface MAX6650/MAX6651
ABSOLUTE MAXIMUM RATINGS
.-0.3V TACH_ .-0.3V +13.2V Other Pins.-0.3V (VCC 0.3V) Output Voltages.-0.3V (VCC 0.3V) Maximum Current Into VCC, GND, VOUT .100mA Into Other Pins .50mA Continuous Power Dissipation +70°C) 10-Pin µMAX (derate 5.6mW/°C above +70°C) .444mW 16-Pin QSOP (derate 8.3mW/°C above +70°C).667mW Operating Temperature Range .-40°C +85°C Junction Temperature .+150°C Storage Temperature Range .-65°C +150°C Lead Temperature (soldering, 10s) .+300°C
Stresses beyond those listed under "Absolute Maximum Ratings" cause permanent damage device. These stress ratings only, functional operation device these other conditions beyond those indicated operational sections specifications implied. Exposure absolute maximum rating conditions extended periods affect device reliability.
ELECTRICAL CHARACTERISTICS
(VCC 3.0V 5.5V, -40°C +85°C, unless otherwise noted. Typical values +25°C 5V.) PARAMETER POWER SUPPLY (VCC) Supply Voltage Supply Current OUTPUT (OUT) Output Voltage Range Output Sink Current Output Source Current TACHOMETER INPUTS (TACH_) Tachometer Threshold Tachometer Input Impedance FEEDBACK (FB) Differential Nonlinearity Useful Resolution Feedback Input Impedance Input Voltage Input High Voltage Input Hysteresis Pullup Resistor Output Sink Current VIL(GPIO_) VIH(GPIO_) VHYS RGPIO_ IGPIO_ VGPIO_ 0.4V 3.6V 3.6V Guaranteed monotonicity (Note Measured (Note bits VTACH_ RTACH_ fan, 4.5V fan, VTACH +1.5 VOUT ISINK ISOURCE IOUT ±100µA VOUT 0.5V VOUT 1.8V Full-on mode, IOUT SYMBOL CONDITIONS UNITS
GENERAL-PURPOSE INPUTS/OUTPUTS (GPIO_) (Note
Fan-Speed Regulators Monitors with SMBus/I2C-Compatible Interface
ELECTRICAL CHARACTERISTICS (continued)
(VCC 3.0V 5.5V, -40°C +85°C, unless otherwise noted. Typical values +25°C 5V.) PARAMETER ADDRESS SELECT (ADD) Input Voltage Input High Voltage External Pulldown Resistor Open Resistance Pullup Current SMBus/I2C INTERFACE (SDA, SCL) Data Output Sink Current Input Leakage Current Input Voltage Input High Voltage Input Hysteresis VHYS 3.6V 3.6V ISDA VSDA 0.6V VIL(ADD) VIH(ADD) RADD ROPEN IADD Selects slave address 1001 (Table Selects slave address 1001 (Table Selects slave address 0011 (Table Minimum resistance GND, selects slave address 0011 (Table VADD 0.5V 0.05V 10.5 SYMBOL CONDITIONS UNITS
MAX6650/MAX6651
TIMING CHARACTERISTICS
(VCC 3.0V 5.5V, -40°C +85°C, unless otherwise noted. Typical values +25°C 5V.) PARAMETER TACHOMETERS Glitch Rejection GPIO2 (Note Clock Frequency Clock Frequency Uncertainty SMBus/I2C fCLK fCLK (Note (Note (Note ISINK (Note 0.1CB(pf) 0.1CB(pf) 0.1CB(pf) Minimum pulse duration SYMBOL CONDITIONS UNITS
INTERFACE (Figures Clock Frequency fSCL Free Time Between Stop Start Condition Hold-Time Start Condition Period Clock High Period Clock Data Hold Time Data Setup Time Rise-Time SDA/SCL Signal (Receiving) Fall-Time SDA/SCL Signal (Receiving) Fall-Time Signal (Transmitting) tBUF tHD:STA tLOW tHIGH tHD:DAT tSU:DAT
Fan-Speed Regulators Monitors with SMBus/I2C-Compatible Interface MAX6650/MAX6651
TIMING CHARACTERISTICS (continued)
(VCC 3.0V 5.5V, -40°C +85°C, unless otherwise noted. Typical values +25°C 5V.) PARAMETER Setup Time Stop Condition Pulse Width Spike Suppressed SYMBOL tSU:STO tSPIKE CONDITIONS UNITS
Note proper measurement VFB, connect shown Typical Operating Circuit. Note GPIO2, GPIO3, GPIO4 only MAX6651. Note Note that transition must internally provide least hold time bridge undefined region (300ns max) SCL's falling edge. Note total capacitance line Tested with 400pF. Rise fall times measured between VCC.
Typical Operating Characteristics
+25°C, unless otherwise noted.)
INTERNAL OSCILLATOR FREQUENCY SUPPLY VOLTAGE
MAX6650/51-01
INTERNAL OSCILLATOR FREQUENCY TEMPERATURE
MAX6650/51-02
FEEDBACK VOLTAGE TEMPERATURE
MAX6650/51-03
FEEDBACK VOLTAGE VFAN 12.0V, VFAN 5.5V 3.0V 5.5V, VFAN 5.5V, VFAN 12.0V
FREQUENCY (kHz)
FREQUENCY (kHz) 5.5V
3.0V
SUPPLY VOLTAGE
TEMPERATURE (°C)
TEMPERATURE (°C)
FEEDBACK VOLTAGE SUPPLY VOLTAGE (DAC
MAX6650/51-04
SUPPLY CURRENT SUPPLY VOLTAGE
MAX6650/51-05
SUPPLY CURRENT TEMPERATURE
5.5V SUPPLY CURRENT (mA)
MAX6650/51-06
2.20 2.15 FEEDBACK VOLTAGE 2.10 2.05 2.00 1.95 1.90 1.85 1.80 VFAN 12.0V VFAN 5.5V
SUPPLY CURRENT (mA)
SUPPLY VOLTAGE TEMPERATURE (°C)
SUPPLY VOLTAGE
Fan-Speed Regulators Monitors with SMBus/I2C-Compatible Interface
Description
MAX6650 NAME MAX6651 TACH0 TACH2, TACH3, TACH1 GPIO4, GPIO3 GPIO1 GPIO0 GPIO2 Tachometer Input. Used close loop around tachometer. Tachometer Inputs. Used monitor tachometers only. Ground 2-Wire Serial-Data Input/Output (open drain) 2-Wire Serial Clock Input Slave Address Select Input (Table General-Purpose Input/Output (open drain) General-Purpose Input/Output (open drain). Configurable either output input (FULL general purpose). General-Purpose Input/Output (open drain). Configurable general input/output line active-low ALERT output. General-Purpose Input/Output (open drain). Configurable general input/output line, internal clock output, external clock input. Output. Drives external MOSFET bipolar transistor. +3.0V +5.5V Power Supply Feedback Input. Closes loop around external MOSFET bipolar transistor. FUNCTION
MAX6650/MAX6651
Detailed Description
MAX6650/MAX6651 SMBus/I2C-Compatible interface regulate monitor speed 5VDC/12VDC brush-less fans with built-in open-collector/drain tachometers. Regulating speed proportionally with temperature saves power, increases life, reduces acoustic noise. Since speed proportional voltage across fan, MAX6650/MAX6651 control speed regulating voltage side with external MOSFET bipolar transistor. MAX6650/MAX6651 each contain internal control loops. first loop controls voltage across fan. internal digital-to-analog converter (DAC) sets reference voltage internal amplifier (Figure which then drives gate external N-channel MOSFET base bipolar transistor) regulate voltage side fan. reference voltage provided changes, feedback amplifier automatically adjusts feedback voltage, which changes voltage across fan.
second control loop consists internal digital logic that controls fan's speed. MAX6650/ MAX6651 control speed forcing tachometer frequency equal reference frequency Fan-Speed Register, prescaler, internal oscillator (see Fan-Speed Register section). When tachometer frequency high, value DAC's input register increased regulator. Once voltage increases, analog control loop forces feedback voltage rise, which reduces voltage across fan. Since speed proportional voltage across fan, slows down.
2-Wire SMBus/I2C-Compatible Digital Interface
From software perspective, MAX6650/MAX6651 appear byte-wide registers that contain speed control, tachometer count, alarm conditions, configuration bits. These devices standard SMBus/I2C-compatible 2-wire serial interface access internal registers.
Fan-Speed Regulators Monitors with SMBus/I2C-Compatible Interface MAX6650/MAX6651
VFAN
5.5V
SMBus/I2C INTERFACE SPEED
MAX6650 MAX6651
TACH0
SMBus/I2C INTERFACE
CONFIGURE ALARM ENABLE ALARM STATUS TACH COUNT COUNT TIME GPIO GPIO STATUS CONTROL LOGIC TACHOMETER COUNT
VOFFSET
ADDRESS DECODE
8-BIT VREF GPIO BLOCKS (FIGURE
GPIO0 GPIO1
ALERT FULL
Figure Block Diagram
MAX6650/MAX6651 employ three standard SMBus protocols: write byte, read byte, receive byte (Figure shorter protocol (receive) allows quicker transfers, provided that correct data register previously selected write read byte instruction. caution with shorter protocol multimaster systems, since second master could overwrite command byte without informing first master.
Table Slave Address Decoding (ADD)
ADDRESS BINARY connection (high-Z) resistor 1001 1001 0011 0011
Slave Addresses
device address four different values. Accomplish this pin-strapping that more than MAX6650/MAX6651 reside same without address conflicts (Table
Fan-Speed Regulators Monitors with SMBus/I2C-Compatible Interface MAX6650/MAX6651
ADDRESS bits Slave Address COMMAND bits Command byte: Selects which register writing DATA bits Data byte: Data goes into register command byte thresholds, configuration masks, sampling rate).
Figure SMBus Protocol: Write Byte Format
ADDRESS bits Slave Address
COMMAND bits Command byte: Selects which register reading from.
ADDRESS bits Slave Address. Repeated change data-flow direction
DATA bits Data byte: Reads from register command byte.
Figure SMBus Protocol: Read Byte Format
ADDRESS bits Slave Address
DATA bits Data byte: Reads data from register commanded last read-byte write-byte transmission; also used SMBus alert response return address.
Figure SMBus Protocol: Receive Byte Format Start condition Stop condition Shaded Slave transmission Acknowledged acknowledged Write Read
Fan-Speed Regulators Monitors with SMBus/I2C-Compatible Interface MAX6650/MAX6651
tLOW tHIGH
SMBCLK
SMBDATA
tSU:STA
tHD:STA
tSU:DAT
tHD:DAT ACKNOWLEDGE CLOCKED INTO MASTER DATA CLOCKED INTO SLAVE DATA CLOCKED INTO SLAVE SLAVE PULLS SMBDATA LINE
tSU:STO tBUF ACKNOWLEDGE CLOCKED INTO MASTER ACKNOWLEDGE CLOCK PULSE STOP CONDITION, DATA EXECUTED SLAVE START CONDITION
START CONDITION ADDRESS CLOCKED INTO SLAVE ADDRESS CLOCKED INTO SLAVE CLOCKED INTO SLAVE SLAVE PULLS SMBDATA LINE
Figure SMBus Write Timing Diagram
tLOW
tHIGH
SMBCLK
SMBDATA
tSU:STA tHD:STA START CONDITION ADDRESS CLOCKED INTO SLAVE ADDRESS CLOCKED INTO SLAVE CLOCKED INTO SLAVE
tSU:DAT SLAVE PULLS SMBDATA LINE ACKNOWLEDGE CLOCKED INTO MASTER DATA CLOCKED INTO MASTER DATA CLOCKED INTO MASTER
tSU:STO ACKNOWLEDGE CLOCK PULSE STOP CONDITION START CONDITION
tBUF
Figure SMBus Read Timing Diagram
Command-Byte Functions
8-bit Command-Byte Register (Table master index that points various other registers within MAX6650/MAX6651. register's power-on reset (POR) state 0000 0000, that receive-byte transmission protocol that lacks command byte) occurring immediately after returns current speed setting.
tachometer pulses, required Fan-Speed Register value (KTACH) calculated tTACH Speed) KTACH [tTACH KSCALE (fCLK 128)] where speed rotations second (RPS), tTACH period tachometer signal, fCLK internal oscillator frequency (254kHz ±10%), KSCALE prescaler value (see Configuration-Byte Register). Since speed inversely proportional tachometer period, Fan-Speed Register value (KTACH) does linearly control speed (Table Select prescaler value fan's full speed achieved with register value approximately (0100 0000) optimize speed range resolution. MAX6651 controlled external oscilla-
Fan-Speed Register
closed-loop mode, MAX6650/MAX6651 Fan-Speed Register period tachometer signal that controls speed. Fan-Speed Register ignored other modes operation. MAX6650/MAX6651 regulate speed forcing tachometer period (tTACH) equal scaled register value. revolution generates
Fan-Speed Regulators Monitors with SMBus/I2C-Compatible Interface MAX6650/MAX6651
Table Command-Byte Assignments
REGISTER SPEED CONFIG GPIO ALARM ENABLE ALARM TACH0 TACH1 TACH2 TACH3 GPIO STAT COUNT COMMAND 0000 0000 0000 0010 0000 0100 0000 0110 0000 1000 0000 1010 0000 1100 0000 1110 0001 0000 0001 0010 0001 0100 0001 0110 READ WRITE (DEFAULT) STATE h1Fh FUNCTION speed Configuration GPIO definition Alarm enable Alarm status Tachometer count Tachometer count Tachometer count Tachometer count GPIO status Tachometer count time
Table Speed
tTACH KTACH 0000 0000 0000 0001 0000 0010 0001 1110 0001 1111 0010 0000 0100 0000 1111 1000 KSCALE (ms) 15.3 SPEED (RPS) KSCALE 61.1 15.9 30,000 30,000 20,000 1900 1900 1800 SPEED (RPM) KSCALE 7700 7400 7200 3700 30,000 29,000 15,000 3830
*The minimum allowed tachometer period 1ms.
that overrides internal oscillator (see GeneralPurpose Input/Output). When using external oscillator (fOSC), calculate Fan-Speed Register value with fCLK equal Codes above (1111 1000) allowed, will significantly decrease frequency.
fan's full speed achieved with register value approximately (0100 0000) optimize speed range resolution (see Speed Register section). fourth selects operating voltage. fifth sixth bits configure operating mode. MAX6650/MAX6651 have four modes operation: full-on, full-off (shutdown), closed-loop, open-loop. closed-loop operation, external microcontroller (µC) sets desired speed writing 8-bit word Fan-Speed Register (see Fan-Speed Register section). MAX6650/MAX6651 monitor fan's tachometer output automatically adjust voltage
Configuration-Byte Register
Configuration-Byte Register (Table adjusts prescaler, changes tachometer threshold voltage, sets mode operation. three least-significant bits configure prescaler division used scale tachometer period. Select prescaler value
Fan-Speed Regulators Monitors with SMBus/I2C-Compatible Interface MAX6650/MAX6651
Table Configuration Byte Register
(MSB) NAME (DEFAULT) STATE Always Operating Mode: Software full-on (default) Software (shutdown) Closed-loop operation Open-loop operation Fan/Tachometer Voltage: (default) Prescaler Division: Divide Divide Divide (default) Divide Divide FUNCTION
MODE
5/12V
(LSB)
SCALE
General-Purpose Input/Output
3.0V 5.5V CBYPASS
MAX6650 MAX6651 100k
GPIO STATUS REGISTER GPIO_
GPIO DEFINITION REGISTER
Figure General-Purpose Input/Output Structure
across until desired speed reached. Openloop operation allows regulate speed directly. reads speed from Tachometer-Count Register. Based tachometer count, decides speed requires adjustment, changes voltage across writing 8-bit word Register. Full-on mode applies maximum voltage across fan, forcing spin full speed. Configuring GPIO1 (see General-Purpose Input/Output section) active-low input provides additional hardware control that fully turns overrides software commands.
GPIO pins connect drain internal Nchannel MOSFET pullup resistor (Figure When N-channel MOSFET (Table pullup resistor provides logic-level high output. However, with MOSFET off, GPIO serve input state read from GPIO Status Register (Table MAX6650/MAX6651 power with MOSFET off, input signals safely connected GPIO pins. When using GPIO general-purpose output, change output writing GPIO Definition Register. GPIO0 configured ALERT output that will whenever fault-condition detected (see Alarm-Enable Status Registers section). GPIO1 configured FULL input allow hardware control fully turn case software failure. GPIO2 (MAX6651 only) configured internal clock output external clock input allow synchronization multiple devices.
Alarm-Enable Status Registers
alarms enabled only when appropriate bits Alarm-Enable Register (Table maximum minimum output level alarms function only when device configured operate closedloop mode (see Configuration-Byte Register section). Alarm Status Register allows system determine which alarm caused alert output (Table set-alarm alert outputs clear after reading
Fan-Speed Regulators Monitors with SMBus/I2C-Compatible Interface MAX6650/MAX6651
Table GPIO Definition Register
(DEFAULT) STATE STATE FUNCTION
(MSB)
GPIO4 (MAX6651 only) GPIO3 (MAX6651 only) GPIO2 (MAX6651 only)
GPIO4 outputs logic-level low. GPIO4 outputs logic-level high serves input. GPIO3 outputs logic-level low. GPIO3 outputs logic-level high serves input. GPIO2 serves external clock input. GPIO2 serves internal clock output. GPIO2 outputs logic-level low. GPIO2 outputs logic-level high serves input. GPIO1 outputs logic-level high serves input. GPIO1 serves FULL input. GPIO1 outputs logic-level low. GPIO1 outputs logic-level high serves input. GPIO0 outputs logic-level high serves input. GPIO0 serves ALERT output. GPIO0 outputs logic-level low. GPIO0 outputs logic-level high serves input.
GPIO1
GPIO0
Table GPIO Status Register
(MSB) (LSB) NAME Always GPIO4 (MAX6651 only) GPIO3 (MAX6651 only) GPIO2 (MAX6651 only) GPIO1 GPIO0 (DEFAULT) STATE
Alarm Status Register condition that caused alarm removed.
Tachometer
Tachometer Count Registers record number pulses corresponding tachometer input during period defined Tachometer Count-Time Register.
MAX6651 contains three additional tachometer inputs, which used monitor additional fans. accurate control multiple fans, identical fans. Tachometer Count-Time Register sets integration time over which MAX6650/MAX6651 count tachometer pulses. devices count (FFh) pulses during selected count time. more than pulses occur, sets overflow alarm Tachometer Count Register reports maximum value 255. time register count register will overflow under worst-case conditions (maximum speed) while maximizing resolution. Calculate maximum measurable speed minimum resolution with following equations: Speed RPS) tCOUNT) Resolution RPS) tCOUNT) where tCOUNT tachometer count time; 1kHz maximum allowable tachometer input frequency MAX6650/MAX6651.
Fan-Speed Regulators Monitors with SMBus/I2C-Compatible Interface MAX6650/MAX6651
Table Alarm-Enable Register Masks
(MSB) (LSB) Enabled NAME GPIO2 (MAX6651 only) GPIO1 TACH (DEFAULT) STATE Always GPIO2 Alarm Enable/Disable (MAX6651 only) GPIO1 Alarm Enable/Disable Tachometer Overflow Alarm Enable/Disable Minimum Output Level Alarm Enable/Disable Maximum Output Level Alarm Enable/Disable FUNCTION
Table Alarm Status Register Assignments
(MSB) (LSB) Alarm condition NAME GPIO2 (MAX6651 only) GPIO1 TACH (DEFAULT) STATE Always GPIO2 Alarm. when GPIO2 (MAX6651 only). GPIO1 Alarm. when GPIO1 low. Tachometer Overflow Alarm Minimum Output Level Alarm Maximum Output Level Alarm FUNCTION
Table Tachometer Count-Time Register
(Assumes pulses revolution) REGISTER VALUE (KCOUNT) 0000 0000 0000 0001 0000 0010 0000 0011 COUNT TIME 0.25 MAXIMUM SPEED (RPS) MINIMUM RESOLUTION (Hz/COUNT) 0.25
Upon power-up, Tachometer Count Registers reset Tachometer Count-Time Register sets integration time.
Digital-to-Analog Converter
When using open-loop mode operation, Register sets voltage side fan. internal operational amplifier compares feedback voltage (VFB) with reference voltage 8-bit DAC, adjusts output voltage (VOUT) until input voltages equal. voltage determined following equation: VREF KDAC) voltage across KDAC VFAN VREF where KDAC numerical value Register VREF 1.5V. minimum feedback voltage limited voltage drop across external MOSFET (RON IFAN), maximum voltage limited fan's supply voltage (VFAN). linear opera-
first bits Tachometer Count-Time Register always zero, last bits count time (Table count time determined from following equation: tCOUNT 0.25s 2KCOUNT
where KCOUNT numerical value 2LSBs. 0.25 factor ±10% uncertainty.
Fan-Speed Regulators Monitors with SMBus/I2C-Compatible Interface MAX6650/MAX6651
VFAN 5.5V
MAX6650
SMBus/I2C INTERFACE TACH0
ALERT FULL
GPIO0 GPIO1
CCOMP 10µF
Figure Control with Bipolar Transistor
tion, values between TB0h (see Typical Operating Characteristics). When using closed-loop mode operation, contents Register ignored. When writing DAC, wait least 500µs before attempting read back.
Power-on Reset (POR)
MAX6650/MAX6651 have volatile memory. prevent ambiguous power-supply conditions from corrupting data memory causing erratic behavior, voltage detector monitors clears memory falls below 1.6V. When power first applied rises above 1.6V, logic blocks begin operating (though reads writes levels below recommended). Power-up defaults include following: alarms disabled. Prescale divider speed full-on mode. Table default states registers.
breakdown voltage, current rating, drain-to-source on-resistance DS(ON)). Gate-to-source conduction threshold must compatible with available VCC. maximum gate-to-source voltage drain-tosource breakdown voltage rating should both least volts higher than supply voltage (VFAN). Choose MOSFET with maximum continuous drain current rating higher than maximum current. RDS(ON) should practical maximize feedback voltage range. Maximum power dissipation power transistor approximated (VFAN IFAN(MAX)) Bipolar power transistors practical driving small midsize fans (Figure Very-high-current fans require output transistor base current greater than MAX6650's 50mA drive capability. Bipolar Darlington transistors will work have poor saturation characteristics could lose drive voltage.
Resistor Selection
tachometer input voltages (VTACH_) feedback voltage cannot exceed 13.2V (see Absolute Maximum Ratings). When using powered 13.2V greater supply (VFAN), protect these inputs from overvoltage conditions with series resistors. resistance required protect these pins calculated from following equation: RPROTECT [(VFAN(MAX) 13.2V) RIN] 13.2V where VFAN(MAX) worst-case maximum supply voltage used power input
Applications Information
MOSFET Bipolar Transistor Selection
MAX6650/MAX6651 drive external N-channel MOSFET that requires five important parameters proper selection: gate-to-source conduction threshold, maximum gate-to-source voltage, drain-to-source
Fan-Speed Regulators Monitors with SMBus/I2C-Compatible Interface MAX6650/MAX6651
impedance tachometer input (150k max) feedback input (150k max).
Selection
closed-loop operation monitoring, MAX6650/MAX6651 require fans with tachometer outputs. tachometer output typically specified option many models from variety manufacturers. Verify nature tachometer output (open collector, totempole) resultant levels, configure connection MAX6650/MAX6651 accordingly. Note many pulses revolution generated tachometer output (this varies from model model among manufacturers, though pulses revolution most common). Table lists representative manufacturers models they make available with tachometer outputs.
Compensation Capacitor
compensation capacitor needed from fan's side ground stabilize analog control loop. Typically, this capacitor should 10µF, depending type being used, value between 100µF required. proper value been selected when ringing present voltage fan's side.
Table Manufacturers
MANUFACTURER Comair Rotron MODEL OPTION brushless models ordered with optional tachometer output. Tachometer output optional some models. brushless models ordered with optional tachometer output. Panaflo flat unidirectional miniature fans ordered with tachometer output. Tachometer output optional some models.
Low-Speed Operation
Brushless fans increase reliability replacing mechanical commutation with electronic commutation. lowering voltage across reduce speed, MAX6650/MAX6651 also lowering supply voltage electronic commutation tachometer electronics. voltage supplied lowered far, internal electronics longer function properly. Some following symptoms possible: stop spinning. tachometer output stop generating signal. tachometer output generate more than pulses revolution. problems that occur, supply voltages which they occur, depend which used.
EBM-Papst
Panasonic
Sunon
VFAN 5.5V TACH0 TACH2 ALERT FULL GPIO0 GPIO1 CCOMP
MAX6651 TACH1
SMBus/I2C INTERFACE
Figure Using MAX6651 Control Parallel Fans
Fan-Speed Regulators Monitors with SMBus/I2C-Compatible Interface MAX6650/MAX6651
5.5V
TACH0 TACH1 TACH2
TACH TACH TACH
VOLTAGE
MAX6651
TACH3
TACH TACH TACH TACH TACH TACH TACH TACH
MAX4051
GPIO2 GPIO3 GPIO4 ADDA ADDB ADDC
Figure Monitoring Multiple Fans
very rough rule thumb, fans expected experience problems somewhere around their rated speed.
Predicting Future Failure
systems that require maximum reliability, such servers network equipment, advantageous predict failure before actually happens, alert system operator before fails, minimizing down time. MAX6650 allows user monitor fan's condition through following modes. Full-On Mode occasionally (over period days weeks) turning full measuring resultant speed, failing detected trend decreasing speeds given power-supply voltage. Power-up convenient time measure maximum speed. Open-Loop Mode fan's condition also monitored using openloop mode. characterizing while new, failure determined writing predetermined value measuring resultant speed. decrease over time resultant speed indication future failure.
Closed-Loop Mode MAX6650 allows system read value used regulate speed. given speed, significant change required value indicate future problems.
Monitoring More than Fans
MAX6651 monitor four fans time (Figure systems requiring more than four fans, Figure shows application using analog multiplexer (mux) monitor fans. GPIO2, GPIO3, GPIO4 connected mux's address pins. writing appropriate value GPIO pins, desired tachometer gets selected counted TACH3 input. Because TACH inputs doublebuffered, only sampled every other time slot, important wait least times tachometer count time before reading register after changing address. extreme case, total fans monitored using three multiplexers connected TACH1, TACH2, TACH3. connect TACH0 MAX6651 under closed-loop mode.
Application
shown Figure MAX6650 cannot maintain speed regulation, other fans will automatically turned full. This useful high-reliability systems where single failure should cause
Fan-Speed Regulators Monitors with SMBus/I2C-Compatible Interface MAX6650/MAX6651
ALERT GPIO0
MAX6650
FULL ALERT
GPIO1 GPIO0
MAX6650
FULL ALERT
GPIO1 GPIO0
MAX6650
FULL ALERT
GPIO1 GPIO0
MAX6650
FULL
GPIO1
Figure Application
downtime. system should designed that number fans used more than actually needed. This way, there sufficient cooling even fails. With fans operating correctly, unnecessary fans their maximum speed. Reducing speed reduce noise increase life fans. However, once fails, important that remaining fans spin their maximum speed. Figure GPIO0s configured ALERT outputs, GPIO1s configured FULL inputs. MAX6650 generates ALERT (indicating failure), remaining MAX6650s will automatically turn their fans full.
ured FULL input. MAX6501 TOVER goes whenever temperature goes above preset value. This pulls FULL (GPIO1) low, forcing spin maximum speed. Figure shows multiple MAX6501s. MAX6501 open-drain output, allowing multiple devices wire ORed FULL input. This configuration allows fail-safe monitoring multiple locations around system.
Hot-Swap Application
swapping detected using circuit Figure where GPIO2 configured generate alert whenever pulled low. long card connected, GPIO2 high. However, when card removed, 2.2k resistor pulls GPIO2 low, causing interrupt. This signals system that swap occurring.
Temperature Monitoring Control
circuit shown Figure provides complete temperature monitoring control. MAX1617A remote/local temperature serial interface with SMBus) monitors temperature with diode-connected transistor. Based temperature readings provided MAX1617A, adjust speed proportionally with temperature. Connecting ALERT output MAX1617A FULL input MAX6650/MAX6651 (see General-Purpose Input/ Output section) allows turn fully MAX1617A detects overtemperature condition. MAX6501 Hardware Fail-Safe Figure shows application using MAX6501 hardware fail-safe. MAX6650 GPIO1 config16
Step-by-Step Part Selection Software Setup
Determining System Topology
MAX6650/MAX6651 support three system topologies. These single control, parallel control, synchronized control. Single Control simplest configuration single MAX6650 each fan. more fans required system, then additional MAX6650 controllers used (one fan). advantage this configuration ability
Fan-Speed Regulators Monitors with SMBus/I2C-Compatible Interface MAX6650/MAX6651
ADD1
ADD0 STBY
MAX1617A
TEMPERATURE SENSOR
INTERRUPT ALERT
GPIO0
ALERT
GPIO1
FULL
MAX6650 MAX6651
VFAN
TACH0
Figure Temperature Monitoring Control
Fan-Speed Regulators Monitors with SMBus/I2C-Compatible Interface MAX6650/MAX6651
VFAN 5.5V VCCIN
MAX6650
SMBus/I2C INTERFACE ALERT GPIO0 CCOMP 10µF TACH0
MAX6501
FULL
TOVER
GPIO1
Figure MAX6501 Hardware Fail-Safe
VFAN 5.5V VCCIN
MAX6650
SMBus/I2C INTERFACE ALERT
MAX6501
GPIO0
TACH0
TOVER FULL
MAX6501
GPIO1
CCOMP 10µF
TOVER
MAX6501
TOVER
Figure MAX6501 Hardware Fail-Safe
independently control each fan. disadvantage cost, size, complexity. single control, MAX6650 (unless additional GPIOs needed). Parallel Control multiple fans required independent control not, then single MAX6650/MAX6651 connected more fans parallel make sense (Figure obvious advantage simplicity, size, cost
savings. fans connected parallel same type, they will tend similar speeds. However, more fans wearing out, speed mismatches occur. MAX6651 allows system monitor four fans, ensuring significant speed mismatches detected. parallel control while monitoring four speeds, select MAX6651.
Fan-Speed Regulators Monitors with SMBus/I2C-Compatible Interface MAX6650/MAX6651
VFAN 5.5V VCCIN HOT-SWAP SECTION
MAX6651
SMBus/I2C INTERFACE ALERT GPIO0 CCOMP 10µF TACH0
FULL GPIO1
GPIO2 2.2k
Figure Hot-Swap Application
parallel control while monitoring only single fan, select MAX6650. Synchronized Control (MAX6651 Only) systems with multiple fans, audible beat frequency sometimes detected speed mismatch. This happens systems where fans connected parallel systems with MAX6650 controlling each fan. parallel systems, speed mismatches occur because fans identical. Slight mechanical variations loading differences result enough speed mismatch cause audible beat. Even systems where there MAX6650/MAX6651 each fan, there still speed mismatches. This primarily oscillator tolerance. MAX6650/MAX6651 oscillator tolerance specified ±10%. worst case, this could result (one high, low) speed mismatch. solution single MAX6651 each fan, configure parts shared clock. shared clock either external system clock MAX6651's internal clocks. external clock used, frequency range from approximately 50kHz 500kHz.
synchronized control, select MAX6651. Combination more complex systems, combination some above control types needed.
Choosing
Once topology chosen, next step choose fan. appropriate section. Enter zero configuration register fan. Configuring this also adjusts tachometer input threshold voltage. This optimizes operation MAX6650/MAX6651 operating voltage being used.
Setting Mode Operation
MAX6650/MAX6651 have four modes operation determined bits configuration register: full full off, open loop, closed loop. Full-On full-on mode applies maximum available voltage across fan, guaranteeing maximum cooling. Full-on mode entered through software hard-
Fan-Speed Regulators Monitors with SMBus/I2C-Compatible Interface MAX6650/MAX6651
ware control. enter full-on mode through hardware, Setting GPIOs section. Note that hardware full-on overrides other modes. Configure MAX6650/MAX6651 software full-on mode entering into bits configuration register. Full-Off full-off mode removes voltage across fan, causing stop. Because MAX6650/ MAX6651 work controlling voltage side fan, either will both leads. Enter full-off mode entering into bits configuration register. Open Loop open-loop mode, MAX6650/MAX6651 actually regulate speed. Speed regulation requires external Although open-loop mode allows maximum flexibility, also requires most software/processor overhead. open-loop mode, MAX6650/MAX6651 SMB/I2C-controlled voltage regulator. adjusts voltage across writing 8-bit value register. This gives direct control voltage across fan. Speed regulation accomplished periodically reading tachometer register(s) adjusting register appropriately. value controls voltage across according following equation: VFAN VFAN_SUPPLY [((R2) VREF KDAC where VFAN voltage across fan, VFAN_SUPPLY supply voltage 12V), (typ), (typ), VREF 1.5V (typ), KDAC value register. Note several important things this equation. First, voltage across moves opposite direction value. other words, values correspond higher voltages across therefore higher speeds. Second, values greater than will result across fan. Similarly, values greater than will produce across fan. This limits useful range from fans fans. Remember that device tolerances cause output voltage value vary significantly from unit unit over temperature. However, because this voltage within closed speed-control loop, such errors corrected loop. Below possible strategy controlling under open-loop mode: power-up, device open-loop mode with value (full speed). Allow speed settle. Read TACH register determine speed. Gradually increase register value steps until desired speed obtained. open-loop mode, four tachometer registers (MAX6651) used measure regulate fan's speed. This especially useful parallel systems where four fans will controlled unit. Care must taken with this mode prevent instability, which caused trying update speed often increments that large. Instability result speeding slowing down repeatedly. Determining proper update rate, shown following steps, depends largely fan's mechanical time constant system's loop gain (DAC step sizes): Enter open-loop mode setting bits control register Determine speed fan(s) reading TACH register(s). Increase decrease register decrease increase voltage across fan, thereby adjusting speed. Closed Loop closed-loop mode, SMBus/I2C master (usually writes desired speed MAX6650/ MAX6651, device automatically adjusts voltage across maintain this speed. This operation mode requires less software/processor overhead than open-loop mode. Once desired speed been written, MAX6650/MAX6651 control fan's speed independently, with intervention required from master. desired, MAX6650/ MAX6651 configured generate interrupt unable regulate fan's speed desired value (see Setting Alarms). MAX6650/MAX6651 regulate only speed connected TACH0 input. Fans connected parallel TACH0 will tend similar speeds (assuming similar fans). When going from full-off closed-loop-mode, recommended following this sequence: Full-off mode Full-on mode (with sufficient pause initiate movement) Closed-loop mode
Fan-Speed Regulators Monitors with SMBus/I2C-Compatible Interface MAX6650/MAX6651
MAX6650 regulates speed following manner. output internal 254kHz oscillator divided 128, generating roughly 2kHz signal. This signal divided plus value speed register used reference frequency. example, speed register will result 667Hz [2kHz (02h+1)] reference frequency, which then compared against frequency tachometer input divided prescaler value. MAX6650/MAX6651 attempt keep tachometer frequency divided prescaler equal reference frequency adjusting voltage across fan. tachometer frequency divided prescaler value less than reference frequency, voltage across increased. Remember that tachometer will give pulses revolution fan. following equations describe operation. When regulation: [fCLK (128 (KTACH 1))] FanSpeed KSCALE where fCLK oscillator frequency (either 254kHz internal oscillator externally applied clock), KTACH value speed register, FanSpeed speed revolutions second (Hz), KSCALE prescaler value 16). Solving four variables: KTACH [(fCLK KSCALE) (256 FanSpeed)] KSCALE [256 FanSpeed (KTACH fCLK FanSpeed KSCALE fCLK [256 (KTACH fCLK FanSpeed (KTACH KSCALE internal oscillator used, setting fCLK 254kHz further reduce equations: Equation KSCALE FanSpeed (KTACH Equation KTACH (992 KSCALE FanSpeed) Equation FanSpeed KSCALE (KTACH Enter closed-loop mode entering into bits configuration register. Note that equation speed inversely proportional (KTACH This means regulated speed nonlinear function value written speed register. values written speed register result large relative changes speed. best results, design system that small values (such 02h) needed. This easily accomplished because 8-bit speed register used, fan-speed control should rarely need more than speeds. good compromise design system selecting appropriate prescaler value) that maximum-rated speed occurs when speed register equals approximately (decimal). Although good target value, values between will work fine. prescaler value also affects response time stability speed-control loop. Adjusting prescaler value effectively adjusts loop gain. larger prescaler value will slow response time increase stability, while smaller prescaler value will yield quicker response time. optimum prescaler value response time stability depends fan's mechanical time constant. Small, fast-spinning fans will tend have small mechanical time constants benefit from smaller prescaler values. good rule thumb selected prescaler value target system. KTACH around full scale, watch overshoot oscillation speed. Also look overshoot oscillation when KTACH changed from value another (e.g., from full-scale speed full scale). there unacceptable overshoot speeds slows down with KTACH constant value; increase prescaler value. Enter appropriate prescaler value bits zero configuration register. speed trade-off between cooling requirements, noise, power, wear. general, desirable (within limits) slowest speed that will accomplish cooling goals. This will reduce power consumption, increase life, minimize noise. When calculating desired speed, remember that above equations written rotations second (RPS), where most fans specified rotations minute (RPM). Write desired speed speed register. Example: Assume following: rated 2000RPM 12V. internal oscillator (fCLK 254kHz). Desired speed 1500RPM (25RPS). First, calculate appropriate prescaler value (KSCALE) using equation Attempt KTACH close possible maximum speed 2000RPM. FanSpeed 33.3RPS (2000RPM/60). KTACH Solving equation gives KSCALE 2.18.
Fan-Speed Regulators Monitors with SMBus/I2C-Compatible Interface MAX6650/MAX6651
will start with KSCALE increase stability, could tried, improve response time, could tried). Second, calculate appropriate value Speed Register (KTACH) using equation FanSpeed 25RPS (1500PRM/60). Solving equation gives KTACH KSCALE KTACH KSCALE KTACH Digital GPIOs configured output logic-level low. MAX6650/MAX6651 designed sink 10mA. This high sink current especially useful driving LEDs. GPIO3 GPIO4, write zero appropriate location GPIO definition register. GPIO0, GPIO1, GPIO2, write appropriate location GPIO definition register. Digital High GPIOs configured generate logic-level high. output high generated using open-drain output stage with internal pullup resistor nominally 100k. MAX6650/MAX6651 power-up default state with GPIOs configured output highs. GPIO3 GPIO4, write appropriate location GPIO definition register. GPIO0, GPIO1, GPIO2, write appropriate location GPIO definition register. Digital Input Since logic-level high output open drain with internal pullup, external device actively pull this low. MAX6650/MAX6651 allow user read GPIO value through GPIO status register. Configure GPIO output logic level high (see above). Read state GPIO reading GPIO status register. Alert Output GPIO0 also serve ALERT output. ALERT output designed drive interrupt ALERT output goes whenever enabled alarm condition occurs (see Setting Alarms). Configure GPIO0 ALERT output writing bits GPIO definition register. Full-On Input GPIO1 also configured full-on input. When full-on pulled low, MAX6650/MAX6651 apply full available voltage across fan. This happens independently software mode operation. This particularly valuable feature high-reliability systems, designed prevent software malfunctions from causing system overheating. Configure GPIO1 full-on input writing bits GPIO definition register.
Determining Tachometer Count Time
monitor speed using SMBus/I2C, next step determine tachometer count time. systems running open-loop mode, this necessary. closed-loop full-speed mode, reading tachometer serve valuable check ensure control loop operating properly. MAX6650/MAX6651 8-bit counter count tachometer pulses. This means device count from tachometer pulses before overflowing. MAX6650/MAX6651 accommodate large range speeds allowing counting interval programmed. Smaller/faster fans should smaller count times. Although larger fans could also smaller count times, resolution would suffer. Choose slowest count time that will overflow under worstcase conditions. Fans mechanical devices, their speeds subject large tolerance variations. overflow does occur, counter will read 255. MAX6650/MAX6651 configured generate alert overflow encountered (see Setting Alarms). Note that prescaler value effect TACH0 register. Enter appropriate count-time value tachometer count-time register. Example: Assume rated 2000 RPM. accommodate large tolerance variations, choose count time appropriate maximum speed 3000RPM; 3000RPM 50RPS generates 100Hz pulses/revolution) tachometer signal. Table indicates count time will optimize resolution. With count time, speeds fast 3825RPM monitored without overflow. minimum resolution will 15RPM 0.75% rated speed 2000RPM.
Setting GPIOs
increase versatility, MAX6650/MAX6651 have five general-purpose digital inputs/outputs, respectively. These GPIOs configured through SMBus/I2C.
Fan-Speed Regulators Monitors with SMBus/I2C-Compatible Interface
Synchronizing Fans GPIO2 configured allow multiple MAX6651s synchronize speeds fans they driving (Figure 14). Synchronization accomplished having MAX6651s external clock) serve clock master configuring GPIO2s system clock output. remaining GPIO2s system need configured clock inputs: Electrically connect MAX6651 GPIO2s together. Configure MAX6651's GPIO2s clock output, using GPIO Definition Register (set bits 01). Configure rest GPIO2s clock inputs, using GPIO Definition Register (set bits 00). Configure MAX6651s closed-loop mode. Configure prescaler values equal. Write identical values speed registers.
MAX6650/MAX6651
MAX6501
CLOCK
GPIO2
MAX6501
CLOCK
GPIO2
MAX6501
CLOCK
Setting Alarms
MAX6650/MAX6651 configured generate ALERT output GPIO0 whenever certain events, such control loop regulation, tachometer overflow, GPI01/GPI02 being driven low, occur. This designed enhance "set forget" functionality control system. Configure GPIO0 ALERT output (see above). Minimum/Maximum Output Level Alarm minimum/maximum output level alarms designed warn system when MAX6650/ MAX6651 unable maintain speed regulation closed-loop mode. MAX6650/MAX6651 maintain speed regulation adjusting voltage across fan. desired speed can't attained, these alarms will generated. Possible causes failure attain desired speed include system programming problems, incipient failure, programmed speed that cannot support. minimum output alarm occurs when output 00h. value means that MAX6650/MAX6651 have applied largest available voltage across fan. This typically means unable spin fast desired speed. maximum output alarm occurs when value FFh. value means MAX6650/MAX6651 have tried reduce voltage across Although this would seem indicate spinning faster than desired speed, this should rarely happen. this alarm occurs, probably indicates some type system error.
GPIO2
Figure Synchronizing Fans
Enable minimum/maximum output level alarm setting bits alarm enable register Tachometer Overflow Alarm tachometer counter overflows (reaches count 255), this alarm will set. Enable overflow output level alarm setting alarm enable register GPIO1/2 Pulled Enabling this alarm causes ALERT output whenever GPIO1 GPIO2 pulled low. This will occur independent configuration GPIO1 GPIO2. Enable GPIO1/GPIO2 output level alarms setting bits and/or alarm enable register Clearing ALERT Once ALERT generated, determine which alarm caused ALERT low. this reading Alarm Status Register. ALERT output will stay active (low) even condition that caused alert removed. Reading Alarm Status Register clears ALERT, condition that caused alert gone. condition gone away, ALERT will stay active. Disabling alarm with Alarm Enable Register will cause ALERToutput inactive. Read Alarm Status Register.
Fan-Speed Regulators Monitors with SMBus/I2C-Compatible Interface MAX6650/MAX6651
Configurations
VIEW
TACH0 GPIO0 GPIO1 TACH0 TACH2 TACH3 GPIO4 TACH1
MAX6650
MAX6651
GPIO3 GPIO2 GPIO0 GPIO1
µMAX
QSOP
Fan-Speed Regulators Monitors with SMBus/I2C-Compatible Interface
Package Information
(The package drawing(s) this data sheet reflect most current specifications. latest package outline information, www.maxim-ic.com/packages.)
10LUMAX.EPS
MAX6650/MAX6651
INCHES 0.043 0.006 0.002 0.030 0.037 0.120 0.116 0.118 0.114 0.120 0.116 0.118 0.114 0.199 0.187 0.0157 0.0275 0.037 0.0106 0.007 0.0197 0.0035 0.0078 0.0196
MILLIMETERS 1.10 0.15 0.05 0.75 0.95 3.05 2.95 3.00 2.89 2.95 3.05 2.89 3.00 4.75 5.05 0.40 0.70 0.940 0.177 0.270 0.500 0.090 0.200 0.498
0.6±0.1
0.6±0.1
VIEW
BOTTOM VIEW
GAGE PLANE
FRONT VIEW
SIDE VIEW
PROPRIETARY INFORMATION TITLE:
PACKAGE OUTLINE, uMAX/uSOP
APPROVAL DOCUMENT CONTROL REV.
21-0061
Fan-Speed Regulators Monitors with SMBus/I2C-Compatible Interface MAX6650/MAX6651
Package Information (continued)
(The package drawing(s) this data sheet reflect most current specifications. latest package outline information, www.maxim-ic.com/packages.)
QSOP.EPS
PACKAGE OUTLINE, QSOP .150", .025" LEAD PITCH
21-0055
Maxim cannot assume responsibility circuitry other than circuitry entirely embodied Maxim product. circuit patent licenses implied. Maxim reserves right change circuitry specifications without notice time.
_Maxim Integrated Products, Gabriel Drive, Sunnyvale, 94086 408-737-7600 2006 Maxim Integrated Products Printed registered trademark Maxim Integrated Products, Inc.
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