MAX6639FAEE+ ,2-Channel Temperature Monitor with Dual, Automatic, PWM Fan-Speed ControllerApplications-40°C toDesktop Computers M A X66 3 9 A E E + 0°C to +150°C 16 QSOP+125°CNotebook Comp ..
MAX6639FAEE+T ,2-Channel Temperature Monitor with Dual, Automatic, PWM Fan-Speed ControllerFeatures♦ Two Thermal-Diode InputsThe MAX6639 monitors its own temperature and oneexternal diode-co ..
MAX663CPA ,Dual Mode⑩ 5V/Programmable Vicropower Voltage Regulatorsapplications. The MAX666 has a ppsitive ogtput and MAX6630/D 0°C to +70%. Dice _
includes on-chip ..
MAX663CSA ,Dual Mode⑩ 5V/Programmable Vicropower Voltage RegulatorsELECTRICAL CHARACTERISTICS, MAX663 AND MAX666 (continued)
(VIN = HN, VOUT = HN, TA = +25''C, unl ..
MAX663CSA ,Dual Mode⑩ 5V/Programmable Vicropower Voltage RegulatorsFeatures
The MAX663/664/666 CMOS voltage regulators have . Dual Mode Operation: Fixed +5V or Adlus ..
MAX663CSA+ ,Dual Mode™ 5V Programmable Micropower Voltage RegulatorsELECTRICAL CHARACTERISTICS, MAX663 AND MAX666 (continued)
(VIN = HN, VOUT = HN, TA = +25''C, unl ..
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MAX6639AEE+-MAX6639FAEE+-MAX6639FAEE+T
2-Channel Temperature Monitor with Dual, Automatic, PWM Fan-Speed Controller
General DescriptionThe MAX6639 monitors its own temperature and oneexternal diode-connected transistor or the temperatures
of two external diode-connected transistors, typicallyavailable in CPUs, FPGAs, or GPUs. The 2-wire serial
interface accepts standard System Management Bus
(SMBus) write byte, read byte, send byte, and receivebyte commands to read the temperature data and pro-
gram the alarm thresholds. Temperature data can beread at any time over the SMBus, and three program-
mable alarm outputs can be used to generate inter-
rupts, throttle signals, or overtemperature shutdownsignals.
The temperature data is also used by the internal dual-
PWM fan-speed controller to adjust the speed of up to
two cooling fans, thereby minimizing noise when thesystem is running cool, but providing maximum cooling
when power dissipation increases. Speed control isaccomplished by tachometer feedback from the fan, so
that the speed of the fan is controlled, not just the PWM
duty cycle. Accuracy of speed measurement is ±4%.
The MAX6639 is available in 16-pin QSOP and 16-pin thinQFN 5mm x 5mm packages. It operates from 3.0V to 3.6V
and consumes just 500µA of supply current.
ApplicationsDesktop Computers
Notebook Computers
Projectors
Servers
Networking Equipment
FeaturesTwo Thermal-Diode InputsUp to 25kHz PWM Output FrequencyThree Selectable SMBus AddressesLocal Temperature Sensor1°C Remote Temperature AccuracyTwo PWM Outputs for Fan Drive (Open Drain; Canbe Pulled Up to +13.5V)Programmable Fan-Control CharacteristicsAutomatic Fan Spin-Up Ensures Fan StartControlled Rate-of-Change Ensures UnobtrusiveFan-Speed Adjustments±3% Fan-Speed Measurement AccuracyTemperature Monitoring Begins at POR for Fail-Safe System ProtectionOT
and THERMOutputs for Throttling or ShutdownMeasures Temperatures Up to +150°CMAX6639F is Optimized for n = 1.021 for PenrynCompatibility
2-Channel Temperature Monitor with Dual,
Automatic, PWM Fan-Speed Controller
MAX6639/MAX6639FEVALUATION KIT AVAILABLE
Ordering Information
PARTO PER A T IN G
RANGEEA SU R EM EN T
RANGE
PIN-
PACKAGEA X6 6 3 9 A E E + -40°C to
+125°C0°C to +150°C16 QSOP
MAX6639ATE+-40°C to
+125°C0°C to +150°C16 TQFN - E P *
AX6 639FAEE+ -40°C to
+125°C0°C to +150°C16 QSOP
MAX6639FATE +-40°C to
+125°C0°C to +150°C16 TQFN- E P *
PWM1SCL
SDA
ADD
DXP2
DXN
GND
DXP1
TOP VIEW
MAX6639
QSOPTACH1
PWM2
TACH2
VCC
FANFAIL
THERM
ALERT
MAX6639
*CONNECT EXPOSED
PAD TO GND.
VCC
GND
DXP1
PWM1
SDA
SCL
TACH1
PWM2
TACH2
FANFAIL
THERM
ADDDXP2DXNALERT4119
Pin Configurations
Typical Application Circuit appears at end of data sheet.+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
2-Channel Temperature Monitor with Dual,
Automatic, PWM Fan-Speed Controller
MAX6639/MAX6639F
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(VCC= +3.0V to +3.6V, TA= 0°C to +125°C, unless otherwise noted. Typical values are at VCC= +3.3V,TA= +85°C.) (Note 1)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
VCCto GND..............................................................-0.3V to +4V
PWM1, PWM2, TACH1, and TACH2 to GND......-0.3V to +13.5V
DXP1 and DXP2 to GND..........................-0.3V to +(VCC+ 0.3V)
DXN to GND..........................................................-0.3V to +0.8V
SCL, SDA, THERM, OT, FANFAIL, ADD,
and ALERTto GND..............................................-0.3V to +6V
SDA, OT, THERM, ALERT, FANFAIL,
PWM1, and PWM2 Current.............................-1mA to +50mA
DXN Current.......................................................................±1mA
ESD Protection (all pins, Human Body Model)..................2000V
Continuous Power Dissipation (TA= +70°C)
16-Pin QSOP (derated 8.3mW/°C above +70°C).......667mW
16-Pin TQFN 5mm x 5mm
(derated at 33.3mW/°C above +70°C)................2666.7mW
Operating Temperature Range.........................-40°C to +125°C
Junction Temperature......................................................+150°C
Storage Temperature Range ............................-65°C to +150°C
Lead Temperature (soldering, 10s).................................+300°C
Soldering Temperature (reflow).......................................+260°C
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSOperating Supply Voltage RangeVCC+3.0+3.6V
Standby CurrentSMB static, sleep mode310µA
Operating CurrentInterface inactive, ADC active0.51mA
VCC = +3.3V, +60°C ≤ TA ≤ +100°C and
+60°C ≤ TR ≤ +100°C-1.0+1.0
VCC = +3.3V, +40°C ≤ TA ≤ +100°C and
0°C ≤ TR ≤ +145°C-2.5+2.5
External Temperature Error
MAX6639AEE, MAX6639ATE:
n = 1.008
MAX6639FAEE: n = 1.021
VCC = +3.3V, 0°C ≤ TR ≤ +145°C-3.8+3.8
VCC = +3.3V, +25°C ≤ TA ≤ +100°C-2.0+2.0Internal Temperature Error
MAX6639AEE, MAX6639ATEVCC = +3.3V, 0°C ≤ TA ≤ +125°C-4.0+4.0°C
VCC = +3.3V, +25°C ≤ TA ≤ +100°C-7.7-2.5Internal Temperature Error
MAX6639FAEEVCC = +3.3V, 0°C ≤ TA ≤ +125°C-10.4-0.1°C
Supply Sensitivity of Temperature
Measurement±0.2°C/V
+0.125°CTemperature Resolution11Bits
Conversion Time125ms
Conversion-Rate Timing Error-10+10%
PWM Frequency Error-10+10%
Tachometer AccuracyTA = +60°C to +100°C±3%
High level70100130Remote-Diode Sourcing CurrentLow level7.01013.0µA
DXN Source Voltage0.7V
2-Channel Temperature Monitor with Dual,
Automatic, PWM Fan-Speed Controller
MAX6639/MAX6639F
ELECTRICAL CHARACTERISTICS (continued)(VCC= +3.0V to +3.6V, TA= 0°C to +125°C, unless otherwise noted. Typical values are at VCC= +3.3V,TA= +85°C.) (Note 1)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
DIGITAL INPUTS AND OUTPUTSALERT, FANFAIL, THERM, OT, SDA
ISINK = 6mA0.4Output Low Voltage (Sink
Current) (OT, ALERT, FANFAIL,
THERM, SDA, PWM1, and PWM2)
VOL
PWM1, PWM2, ISINK = 4mA0.4
Output High Leakage Current
(OT, ALERT, FANFAIL, THERM,
SDA, PWM1, and PWM2)
IOH1µA
Logic-Low Input Voltage (SDA,
SCL, THERM, TACH1, TACH2)VIL0.8V
Logic-High Input Voltage (SDA,
SCL, THERM, TACH1, TACH2)VIHVCC = 3.3V2.1V
Input Leakage Current (SDA,
SCL, THERM, TACH1, TACH2)VIN = VCC or GND1µA
Input CapacitanceCIN5pF
SMBus TIMING (Note 2)Serial Clock FrequencyfSCL(Note 3)10100kHz
Clock Low PeriodtLOW10% to 10%4µs
Clock High PeriodtHIGH90% to 90%4.7µs
Bus Free Time Between STOP
and START ConditionstBUF4.7µs
SMBus START Condition Setup
TimetSU:STA90% of SMBCLK to 90% of SMBDATA4.7µs
START Condition Hold TimetHD:STO10% of SDA to 10% of SCL4µs
STOP Condition Setup TimetSU:STO90% of SCL to 10% of SDA4µs
Data Setup TimetSU:DAT10% of SDA to 10% of SCL250ns
Data Hold TimetHD:DAT10% of SCL to 10% of SDA (Note 4)300ns
SMBus Fall TimetF300ns
SMBus Rise TimetR1000ns
SMBus TimeouttTIMEOUT587490ms
Note 1:All parameters tested at a single temperature. Specifications are guaranteed by design.
Note 2:Timing specifications guaranteed by design.
Note 3:The serial interface resets when SCL is low for more than tTIMEOUT.
Note 4:A transition must internally provide at least a hold time to bridge the undefined region (300ns max) of SCL's falling edge.
2-Channel Temperature Monitor with Dual,
Automatic, PWM Fan-Speed Controller
Typical Operating Characteristics(VCC= 3.3V, TA= +25°C.)
STANDBY SUPPLY CURRENT
vs. SUPPLY VOLTAGEMAX6639 toc01
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (
OPERATING SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX6639 toc02
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (
REMOTE TEMPERATURE ERROR
vs. REMOTE-DIODE TEMPERATURE
MAX6639 toc03
TEMPERATURE (°C)
TEMPERATURE ERROR (
°C)
FAIRCHILD 2N3906
LOCAL TEMPERATURE ERROR
vs. DIE TEMPERATUREMAX6639 toc04
TEMPERATURE (°C)
TEMPERATURE ERROR (
LOCAL TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCY
MAX6639 toc06
FREQUENCY (Hz)
TEMPERATURE ERROR (
10k1k100
-2.010100k
VIN = 250mVP-P SQUARE WAVE APPLIED TO
VCC WITH NO BYPASS CAPACITOR
REMOTE TEMPERATURE ERROR
vs. COMMON-MODE NOISE FREQUENCYMAX6639 toc07
FREQUENCY (Hz)
TEMPERATURE ERROR (
10k1k100
0.1110100k
VIN = AC-COUPLED TO DXP AND DXN
VIN = 100mVP-P SQUARE WAVE
REMOTE TEMPERATURE ERROR
vs. DIFFERENTIAL NOISE FREQUENCYMAX6639 toc08
FREQUENCY (Hz)
TEMPERATURE ERROR (
°C)
10k1k100
-2.0100k
VIN = AC-COUPLED TO DXP
VIN = 100mVP-P SQUARE WAVE
TEMPERATURE ERROR
vs. DXP-DXN CAPACITANCEMAX6639 toc09
DXP-DXN CAPACITANCE (nF)
TEMPERATURE ERROR (1
MAX6639/MAX6639F
REMOTE TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCY
MAX6639 toc05
FREQUENCY (Hz)
TEMPERATURE ERROR (
10k1k100
-2.0100k
VIN = 250mVP-P SQUARE WAVE APPLIED TO
VCC WITH NO BYPASS CAPACITOR
2-Channel Temperature Monitor with Dual,
Automatic, PWM Fan-Speed Controller
MAX6639/MAX6639F
PINQ FN - EPQSOPNAMEFUNCTION1, 153, 1PWM2,
PWM1
Open-Drain Output to Power-Transistor Driving Fan. Connect to the gate of a MOSFET or base of a
bipolar transistor. PWM_ requires a pullup resistor. The pullup resistor can be connected to a
supply voltage as high as 13.5V, regardless of the MAX6639’s supply voltage.
2, 164, 2TACH2,
TACH1
Tachometer Inputs. Connect to the tachometer output of the fan. TACH_ requires a pullup resistor.
The pullup resistor can be connected to a supply voltage as high as 13.5V, regardless of the
MAX6639’s supply voltage.FANFAILActive-Low, Open-Drain, Fan-Failure Output. Open circuit when VCC = 0.THERMActive-Low, Open-Drain Thermal Alarm Output. Typically used for clock throttling. Open circuit
when VCC = 0.OTActive-Low, Open-Drain Overtemperature Output. Typically used for system shutdown or clock
throttling. Can be pulled up to 5.5V regardless of VCC. Open circuit when VCC = 0.VCCPower-Supply Input. 3.3V nominal. Bypass VCC to GND with a 0.1µF capacitor.10GNDGround. Connect to a clean ground reference.
8, 109, 12DXP1,
DXP2om b i ned C ur r ent S our ce and A/D P osi ti ve Inp ut for Rem ote D i od e. C onnect to anod e of r em ote- i od e- connected tem p er atur e- sensi ng tr ansi stor . D o not l eave unconnected ; connect to D X N i f noem ote d i od e i s used . P l ace a 2200p F cap aci tor b etw een D X P _ and D X N for noi se fi l ter i ng .
911DXNRem ote D i od e C ur r ent S i nk Inp ut. C onnect C athod e of the Rem ote- D i od e- C onnected Tr ansi stor to D X N 13ADDAddress Input. Sets device slave address. Connect to GND, VCC, or leave unconnected to give
three unique addresses. See Table 1.14ALERTActive-Low, Open-Drain SMBus Alert Output16SCLSMBus Serial-Clock Input. Can be pulled up to 5.5V regardless of VCC. Open circuit when VCC =15SDASMBus Serial-Data Input/Output, Open Drain. Can be pulled up to 5.5V regardless of VCC. Open
circuit when VCC = 0.EP
Exposed Pad (TQFN package only). Internally connected to GND. Connect EP to a large PCB pad
for optimum performance and enhanced thermal dissipation. Not intended as an electrical
Pin Description
Typical Operating Characteristics (continued)(VCC= 3.3V, TA= +25°C.)
PWMOUT FREQUENCY
vs. DIE TEMPERATUREMAX6639 toc10
TEMPERATURE (°C)
PWMOUT FREQUENCY (Hz)603510-15
PWMOUT FREQUENCY
vs. SUPPLY VOLTAGE
MAX6639 toc11
SUPPLY VOLTAGE (V)
PWMOUT FREQUENCY (Hz)
3.05.5
Detailed DescriptionThe MAX6639 monitors its own temperature and a
remote-diode-connected transistor or the temperatures
of two external-diode-connected transistors, which typi-
cally reside on the die of a CPU or other integrated cir-
cuit. The 2-wire serial interface accepts standard
SMBus write byte, read byte, send byte, and receive
byte commands to read the temperature data and pro-
gram the alarm thresholds. Temperature data can be
read at any time over the SMBus, and a programmable
alarm output can be used to generate interrupts, throt-
tle signals, or overtemperature shutdown signals.
The temperature data is also used by the internal dual-
PWM fan-speed controller to adjust the speed of up to
two cooling fans, thereby minimizing noise when the
system is running cool, but providing maximum cooling
when power dissipation increases. RPM feedback
allows the MAX6639 to control the fan’s actual speed.
2-Channel Temperature Monitor with Dual,
Automatic, PWM Fan-Speed Controller
MAX6639/MAX6639FGND
SMBus
INTERFACE AND
REGISTERS
LOGIC
PWM
GENERATOR
BLOCK
VCC
TEMPERATURE
PROCESSING
BLOCK
SDA
SCL
ADD
DXP1
DXN
PWM1
PWM2
TACH1
TACH2
DXP2
THERM
FANFAIL
ALERT
MAX6639
Block Diagram
Write Byte Format
Read Byte Format
Send Byte FormatReceive Byte FormatSlave Address: equiva-
lent to chip-select line of
a 3-wire interface
Command Byte: selects which
register you are writing to
Data Byte: data goes into the register
set by the command byte (to set
thresholds, configuration masks, and
sampling rate)
Slave Address: equiva-
lent to chip-select line
Command Byte: selects
which register you are
reading from
Slave Address: repeated
due to change in data-
flow direction
Data Byte: reads from
the register set by the
command byte
Command Byte: sends com-
mand with no data, usually
used for one-shot command
Data Byte: reads data from
the register commanded
by the last read byte or
write byte transmission;
also used for SMBus alert
response return address
S = START CONDITIONSHADED = SLAVE TRANSMISSION
P = STOP CONDITION/// = NOT ACKNOWLEDGED
Figure 1. SMBus Protocols
ADDRESSRDACKDATA///P7 bits8 bits
SACKCOMMANDACKP8 bits
ADDRESS7 bits
ACKDATA8 bits
ACKCOMMAND8 bits
ACKWRADDRESS7 bits
ADDRESSWRACKCOMMANDACKSADDRESS7 bits8 bits7 bits
ACKDATA8 bits
///P
SMBus Digital InterfaceFrom a software perspective, the MAX6639 appears as
a set of byte-wide registers. This device uses a stan-
dard SMBus 2-wire/I2C-compatible serial interface to
access the internal registers.
The MAX6639 features an address select input (ADD)
that allows the MAX6639 to have three unique addresses
(see Table 1).
The MAX6639 employs four standard SMBus protocols:
write byte, read byte, send byte, and receive byte
(Figures 1, 2, and 3). The shorter receive byte protocol
allows quicker transfers, provided that the correct data
register was previously selected by a read byte instruc-
tion. Use caution with the shorter protocols in multimas-
ter systems, since a second master could overwrite the
command byte without informing the first master.
Table 4 details the register addresses and functions,
whether they can be read or written to, and the power-
on reset (POR) state. See Tables 5–9 for all other regis-
ter functions and the Register Descriptionssection.
Temperature ReadingTemperature data can be read from registers 00h and
01h. The temperature data format for these registers is
8 bits, with the LSB representing 1°C (Table 2) and the
MSB representing +128°C. The MSB is transmitted first.
Three additional temperature bits provide resolution
down to 0.125°C and are in the channel 1 extended
temperature (05h) and channel 2 extended temperature
(06h) registers. All values below 0°C clip to 00h.
2-Channel Temperature Monitor with Dual,
Automatic, PWM Fan-Speed Controller
MAX6639/MAX6639FSCL
A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVECDEFGHIJ
SDA
tSU:STAtHD:STA
tLOWtHIGH
tSU:DATtSU:STOtBUFK
E = SLAVE PULLS SMBDATA LINE LOW
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO SLAVE
H = LSB OF DATA CLOCKED INTO SLAVE
I = MASTER PULLS DATA LINE LOW
J = ACKNOWLEDGE CLOCKED INTO SLAVE
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION
M = NEW START CONDITION
Figure 2. SMBus Write Timing Diagram
SCLCDEFGHIJK
SDA
tSU:STAtHD:STA
tLOWtHIGH
tSU:DATtHD:DATtSU:STOtBUF
A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
E = SLAVE PULLS SMBDATA LINE LOW M
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO MASTER
H = LSB OF DATA CLOCKED INTO MASTER
I = MASTER PULLS DATA LINE LOW
J = ACKNOWLEDGE CLOCKED INTO SLAVE
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION
M = NEW START CONDITION
Figure 3. SMBus Read Timing Diagram
ADD INPUT STATEI2C SLAVE ADDRESSBINARY
EQUIVALENTVCC5Eh0101 111
Floating5Ch0101 110
GND58h0101 100
Table 1. I2C Slave Address
The MAX6639 employs a register lock mechanism to
avoid getting temperature results from the temperature
register and the extended temperature register sam-
pled at two different time points. Reading the extended
register stops the MAX6639 from updating the tempera-
ture register for at least 0.25s, unless there is a temper-
ature register read before the scheduled update. This
allows enough time to read the main register before it is
updated, thereby preventing reading the temperature
register data from one conversion and the extended
temperature register data from a different conversion.
The MAX6639 measures the temperature at a fixed rate
of 4Hz immediately after it is powered on. Setting bit 7
of the configuration register (04h) shuts down the tem-
perature measurement cycle.
OutputWhen a measured temperature exceeds the corre-
sponding OTtemperature threshold and OTis not
masked, the associated OTstatus register bit sets and
the OToutput asserts. If OTfor the respective channel
is masked, the OTstatus register sets, but the OTout-
put does not assert. To deassert the OToutput and the
associated status register bit, either the measured tem-
perature must fall at least 5°C below the trip threshold
or the trip threshold must be increased to at least 5°C
above the current measured temperature.
THERMWhen a measured temperature exceeds the corre-
sponding THERMtemperature threshold and THERMis
not masked, the associated THERMstatus register bit
is set and the THERMoutput asserts. If THERMfor the
respective channel is masked, the THERMstatus regis-
ter is set, but the THERMoutput does not assert. To
deassert the THERMoutput and the associated status
register bit, either the measured temperature must fall
at least 5°C below the trip threshold or the trip threshold
must be increased to at least 5°C above the current
measured temperature. Asserting THERMinternally or
externally forces both PWM outputs to 100% duty cycle
when bit 6 in address 13h (fan 1) or bit 6 in address
17h (fan 2) is set.
ALERTThe ALERToutput asserts to indicate that a measured
temperature exceeds the ALERTtrip threshold for that
temperature channel. The status bit and the ALERTout-
put clear by reading the ALERTstatus register. If the
ALERTstatus bit is cleared, but the temperature still
exceeds the ALERTtemperature threshold, ALERT
reasserts on the next conversion, and the status bit sets
again. A successful alert response protocol clears
ALERTbut does not affect the ALERTstatus bit.
TACH1 and TACH2 InputsTo measure the fan speed, the MAX6639 has two
tachometers. Each tachometer has an accurate internal
clock to count the time elapsed in one revolution.
Therefore, it is counting the time between two tachome-
ter pulses for a fan with four poles. When the PWM sig-
nal is used to directly modulate the fan’s power supply,
the PWM frequency is normally in the 20Hz to 100Hz
range. In this case, the time required for one revolution
may be longer than the PWM on-time. For this reason,
the PWM pulses are periodically stretched to allow
tachometer measurement over a full revolution. Turn off
pulse stretching by setting bit 5 of register 13h or regis-
ter 17h when using a 4-wire fan.
The tachometer count is inversely proportional to the
fan’s RPM. The tachometer count data is stored in regis-
ter 20h (for TACH1) and register 21h (for TACH2).
Reading a value of 255 from the TACH count register
means the fan’s RPM is zero or too slow for the range.
Reading a value of zero in the TACH count register
means the fan’s RPM is higher than the range selected.
Table 2 shows the fan’s available RPM ranges. Use reg-
isters 10h or 14h to select the appropriate RPM range for
the fan being used.
FANFAILThe FANFAILoutput asserts to indicate that one of the
fans has failed or is spinning slower than the required
speed. The MAX6639 detects fan fault depending on the
fan-control mode. In PWM mode, the MAX6639 pro-
duces a square wave with a duty cycle set by the value
2-Channel Temperature Monitor with Dual,
Automatic, PWM Fan-Speed Controller
MAX6639/MAX6639F
TEMP (°C)TEMP (°C)DIGITAL OUTPUT241+2411111 0001
240+2401111 0000
126+1260111 1110+250001 1001
1.5010000 0001
0.0000000 0000
Table 2. Temperature Data Byte Format
FAN RPM
RANGE
INTERNAL CLOCK
FREQUENCY (kHz)Table 3. Tachometer Setting
written to the duty-cycle registers (26h and 27h). In this
mode, the MAX6639 signals a fan fault when the
tachometer count is greater than the maximum tachome-
ter count value stored in the appropriate register (22h
and 23h). After the MAX6639 asserts FANFAIL, the fan
with a tachometer fault goes to full speed for 2s in an
attempt to restart the fan and then returns to the original
duty-cycle settings. Reading the status register clears
the FANFAILstatus bits and the output. The MAX6639
measures the fan speed again after 2s. The MAX6639
asserts FANFAILif it detects the fan fault again.
In RPM mode (either automatic or manual), the
MAX6639 checks for fan failure only when the duty
cycle reaches 100%. It asserts FANFAILwhen the
tachometer count is greater than twice the target
tachometer count. In manual RPM mode, registers 22h
and 23h store the target tachometer count value. In
automatic RPM mode, these registers store the maxi-
mum tachometer count.
Fan-Speed ControlThe MAX6639 adjusts fan speed by controlling the duty
cycle of a PWM signal. This PWM signal then either
modulates the DC brushless fan’s power supply or dri-
ves a speed-control input on a fan that is equipped with
one. There are three speed-control modes: PWM, in
which the PWM duty cycle is directly programmed over
the SMBus;
manual RPM, in which the desiredtachometer count is programmed into a register and
the MAX6639 adjusts its duty cycle to achieve the
desired tachometer count; and
automatic RPM, inwhich the tachometer count is adjusted based on a
programmed temperature profile.
The MAX6639 divides each PWM cycle into 120 time
slots. Registers 26h and 27h contain the current values
of the duty cycles for PWM1 and PWM2, expressed as
the effective time-slot length. For example, the PWM1
output duty cycle is 25% when register 26h reads 1Eh
(30/120).
PWM Control ModeEnter PWM mode by setting bit 7 of the fan 1 or 2 con-
figuration 1 register (10h and 14h) to 1. In PWM control
mode, the MAX6639 generates PWM signals whose
duty cycles are specified by writing the desired values
to fan duty-cycle registers 26h and 27h. When a new
duty-cycle value is written into one of the fan duty-cycle
registers, the duty cycle changes to the new value at a
rate determined by the rate-of-change bits [6:4] in the
fan 1 or 2 configuration 1 register. The rate-of-change
of the duty cycle ranges from 000 (immediately
changes to the new programmed value) to 111
(changes by 1/120 every 4s). See Table 5 and the Fan
1 and 2 Configuration 1 (10h and 14h)section.
Manual RPM Control ModeEnter manual RPM control mode by setting bits 2, 3,
and 7 of the fan 1 or 2 configuration 1 register (10h and
14h) to zero. In the manual RPM control mode, the
MAX6639 adjusts the duty cycle and measures the fan
speed. Enter the target tachometer count in register
22h for fan 1 and register 23h for fan 2. The MAX6639
compares the target tachometer count with the mea-
sured tachometer count and adjusts the duty cycle so
that the fan speed gradually approaches the target
tachometer count.
The first time manual RPM control mode is entered, the
initial PWM duty cycle is determined by the target
tachometer count:
where targetTACH is the value of the target tachometer
count in the target tach count register (22h or 23h).
If the initial duty-cycle value is over 120, the duty cycle
is 100%. If spin-up is enabled (bit 7 in registers 13h
and 17h) and the fan is not already spinning, the duty
cycle first goes to 100% and then goes to the initial
duty-cycle value. Every 2s, the MAX6639 counts the
fan’s period by counting the number of pulses stored in
registers 24h and 25h. If the count is different from the
target count, the duty cycle is adjusted.
If a nonzero rate-of-change is selected, the duty cycle
changes at the specified rate until the tachometer count
is within ±5 of the target. Then the MAX6639 gets into a
locked state and updates the duty cycle every 2s.
Automatic RPM Control ModeIn the automatic RPM control mode, the MAX6639 mea-
sures temperature, sets a target tachometer count
based on the measured temperature, and then adjusts
the duty cycle so the fan spins at the desired speed.
Enter this mode by setting bit 7 of the fan 1 or 2 config-
uration 1 register (10h and 14h) to zero and selecting
the temperature channel that controls the fan speed
using bits 2 and 3 of the configuration register.
In both RPM modes (automatic and manual), the
MAX6639 implements a low limit for the tachometer
counts. This limits the maximum speed of the fan by
ensuring that the fan’s tachometer count does not go
lower than the tachometer count specified by bits 5
through 0 of register 24h for fan 1 and register 25h for
fan 2. Typical values for the minimum tachometer count
InitialdutycycletetTACH arg=−255
2-Channel Temperature Monitor with Dual,
Automatic, PWM Fan-Speed Controller
MAX6639/MAX6639F
are 30h to 60h. Set the value to correspond to the full-
rated RPM of the fan. See Figure 4.
Figure 5 shows how the MAX6639 calculates the target
tachometer value based on the measured temperature.
At TMIN, the fan spins at a minimum speed value corre-
sponding to the maximum tachometer count value
stored in register 22h or 23h. Bit 0 of register 11h (fan
1) and register 15h (fan 2) selects the behavior below
TMIN. If bit 0 is equal to zero, the fan is completely off
below TMIN. When the temperature is falling, it must
drop 5°C below TMINbefore the fan turns off. If bit 0 is
set to 1, the fan does not turn off below TMIN, but
instead stays at the maximum tachometer count in reg-
ister 22h or 23h.
When the measured temperature is higher than TMIN,
the MAX6639 calculates the target tachometer count
value based on two linear equations. The target
tachometer count decreases by the tach step size
value stored in bits 7 through 4 of registers 11h and
15h each time the measured temperature increases by
the temperature step size value stored in bits 2 and 3 of
registers 11h and 15h. As the measured temperature
continues to increase, a second tachometer step size
goes into effect. Bits 3 through 0 of register 12h and
16h select the number temperature/PWM steps after
which the new step size takes effect. The new step size
is selected by bits 7 to 4 of registers 12h and 16h.
Register Descriptions
Channel 1 and Channel 2 Temperature Registers
(00h and 01h)These registers contain the results of temperature mea-
surements. The MSB has a weight of +128°C and the
LSB +1°C. Temperature data for remote diode 1 is in
the channel 1 temperature register. Temperature data
for remote diode 2 or the local sensor (selectable by bit
4 in the global configuration register) is in the channel 2
temperature register. Three additional temperature bits
provide resolution down to 0.125°C and are in the
channel 1 extended temperature (05h) and channel 2
extended temperature (06h) registers. The channel 1
and channel 2 temperature registers do not update until
at least 250ms after the access of the associated
extended temperature registers. All values below 0°C
return 00h.
Status Register (02h)A 1 indicates that an ALERT, THERM, OT, or fan fault has
occurred. Reading this register clears bits 7, 6, 1, and 0.
Reading the register also clears the ALERTand
FANFAILoutputs, but not the THERMand OToutputs. If
the fault is still present on the next temperature measure-
ment cycle, any cleared bits and outputs are set again. A
successful alert response clears the values on the out-
puts but does not clear the status register bits. The
ALERTbits assert when the measured temperature is
higher than the respective thresholds. The THERMandoutputs behave like comparators with 5°C hysteresis.
2-Channel Temperature Monitor with Dual,
Automatic, PWM Fan-Speed Controller
MAX6639/MAX6639FTACHMAX
TACH
0xFFh
TACHMIN
TEMPERATURETBTMIN-5TMIN
TACHB+1
TACHA+1
Figure 4. Tachometer Target Calculation
RPM
RPMMAX
RPMMIN
TEMPERATURE
TMIN-5TMINTB
TACHA+1
TACHB+1
Figure 5. RPM Target Calculation
2-Channel Temperature Monitor with Dual,
Automatic, PWM Fan-Speed Controller
MAX6639/MAX6639F
READ/
WRITE
REGISTER
NO.
ADDRESS
POR
STATEFUNCTIOND7D6D5D4D3D2D1D 0 00h0000
Temperature
channel 1
MSB
(+128°C)——————LS B1° C ) 01h0000
Temperature
channel 2
MSB
(+128°C)——————LS B1° C ) 02h0000
0000Status byteChannel 1
ALERT
Channel 2
ALERT
Channel 1
Channel 2
Channel 1
THERM
Channel 2
THERMFan 1 faultFan 2
faul t
R/W03h0000
0011Output maskChannel 1
ALERT
Channel 2
ALERT
Channel 1
Channel 2
Channel 1
THERM
Channel 2
THERMFan 1 faultFan 2
faul t
R/W04h0011
Global
configuration
Run
0 = run,
1= stby
POR:
1 = reset
SMBus
timeout:
0 =
enabled,
1 =
disabled
Tem p
channel 2
sour ce:
1 = l ocal ,
0 = r em ote
PWM
output
frequency
range
ReservedReservedReser ved 05h0000
Channel 1
extended
temperature
MSB
(0.5°C)—LSB
(0.125°C)ReservedReservedReservedReservedD i od e
faul t06h0000
Channel 2
extended
temperature
MSB
(0.5°C)—LSB
(0.125°C)ReservedReservedReservedReservedD i od e
faul t
R/W08h0101
Channel 1
ALERT limitMSB——————LS B1° C )
R/W09h0101
Channel 2
ALERT limitMSB——————LS B1° C )
R/W0Ah0110
Channel 1 OT
limitMSB——————LS B1° C )
R/W0Bh0110
Channel 2 OT
limitMSB——————LS B1° C )
R/W0Ch0101
Channel 1
THERM limitMSB——————LS B1° C )
R/W0Dh0101
Channel 2
THERM limitMSB——————LS B1° C )
R/W10h1000
Fan 1
configuration
PWM
mode
Rate of
change
(MSB)
Rate of
change
Rate of
change
(LSB)
Fan 1
channel 1
control
Fan 1
channel 2
control
RPM
range
select
RP M ang e
sel ect
R/W11h0000
Fan 1
Configuration
RPM step-
size A
(MSB)
RPM step-
size A
RPM step-
size A
RPM step-
size A
(LSB)
Temp
step-size
A (MSB)
Temp
step-size
A (LSB)
PWM
Polarityi ni m um
fan
sp eed :
0 = 0%,
1= val ue
Table 4. Register Map
