MAX1669 ,Fan Controller and Remote Temperature Sensor with SMBus Serial InterfaceApplicationsMAX1669EEE -40°C to +85°C 16 QSOP®Pentium CPU CoolingDesktop ComputersPin Configuration ..
MAX1669EEE ,Fan Controller and Remote Temperature Sensor with SMBus Serial InterfaceApplicationsMAX1669EEE -40°C to +85°C 16 QSOP®Pentium CPU CoolingDesktop ComputersPin Configuration ..
MAX166BCWP ,CMOS レP-Compatible, 5レs, 8-Bit ADCs19-1976, Rev l 6/92
lVI/JXI/I/l
CMOS M'AtompatiMe, Sps,
MAX1672EEE ,Step-Up/Down DC-DC Converter in QSOP PackageApplications______________Ordering InformationSingle-Cell, Lithium-Powered 2-Cell to 4-Cell AA Alka ..
MAX1672EEE+ ,Step-Up/Down DC-DC Converter in QSOP PackageApplicationsOrdering InformationSingle-Cell, Lithium-Powered 2-Cell to 4-Cell AA AlkalinePART TEMP ..
MAX1672EEE+T ,Step-Up/Down DC-DC Converter in QSOP PackageELECTRICAL CHARACTERISTICS(V = 6V, C = 0.1µF, C = 4.7µF, T = -40°C to +85°C, unless otherwise noted ..
MAX4427CSA ,Dual High-Speed 1.5A MOSFET Drivers
MAX4427CSA ,Dual High-Speed 1.5A MOSFET Drivers
MAX4427CSA+ ,Dual High-Speed, 1.5A MOSFET Drivers
MAX4427CSA+ ,Dual High-Speed, 1.5A MOSFET Drivers
MAX4427CSA+T ,Dual High-Speed, 1.5A MOSFET Drivers
MAX4427CSA-T ,Dual High-Speed, 1.5A MOSFET Drivers
MAX1669
Fan Controller and Remote Temperature Sensor with SMBus Serial Interface
General DescriptionThe MAX1669 fan controller includes a precise digital
thermometer that reports the temperature of a remote
sensor. The remote sensor is a diode-connected transis-
tor—typically a low-cost, easily mounted 2N3906 PNP
type—replacing conventional thermistors or thermocou-
ples. Remote accuracy is ±3°C for transistors from multi-
ple manufacturers, with no calibration needed. The
MAX1669 has an independent fan controller with a low-
current logic output requiring external power compo-
nents to interface to a DC brushless fan. The fan
controller has two modes of operation: a low-frequency
(20Hz to 160Hz) PWM mode intended for driving the fan
motor, or a high-impedance DAC output that generates
a variable DC control voltage. In PWM mode, the FAN
frequency can be synchronized to an external clock.
Other key features include general-purpose inputs/out-
puts (GPIOs) for fan presence detection and a thermo-
stat output intended as a fan override signal in case the
host system loses the ability to communicate. The inter-
nal ADC has a wide input voltage range and gives
overrange readings when too large an input voltage is
applied. Other error-checking includes temperature
out-of-range indication and diode open/short faults.
The MAX1669 is available in a space-saving 16-pin
QSOP package that allows it to fit adjacent to the
SLOT1 connector.
ApplicationsPentium®CPU Cooling
Desktop Computers
Notebook Computers
Servers
Workstations
FeaturesMeasures Remote CPU TemperatureNo Calibration Required20Hz to 160Hz PWM Output for FanPWM Frequency Sync Input (260kHz)Flexible Fan Interface: Linear or PWMSMBus 2-Wire Serial InterfaceProgrammable Under/Overtemperature AlarmsALERT
Latched Interrupt OutputOVERT
Thermostat OutputTwo GPIO PinsWrite-Once Configuration ProtectionSupports SMBus Alert Response±3°C Temperature Accuracy (-40°C to +125°C,
remote)3µA Standby Supply Current+3V to +5.5V Supply RangeSmall 16-Pin QSOP Package
MAX1669
Fan Controller and Remote Temperature Sensor
with SMBus Serial InterfaceI/O1OVERT
ALERT
SMBDATA
SMBCLK
PGND
FAN
SYNC
VCC
TOP VIEW
MAX1669
QSOPI/O2
ADD0
AGND
ADD1
ADD2
DXN
DXP
19-1574; Rev 0; 1/00
PARTMAX1669EEE-40°C to +85°C
TEMP. RANGEPIN-PACKAGE16 QSOP
Pentium is a registered trademark of Intel Corp.
Pin Configuration
Ordering Information
Typical Operating Circuit appears at end of data sheet.
MAX1669
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(VCC= +3.3V, TA
= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)
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 AGND...........................................................-0.3V to +6V
DXP, ADD_ to AGND.................................-0.3V to (VCC+ 0.3V)
DXN to AGND.......................................................-0.3V to +0.8V
SMBCLK, SMBDATA, ALERT, SYNC,
I/O1, I/O2, OVERT, FAN to AGND......................-0.3V to +6V
FAN to PGND............................................-0.3V to (VCC+ 0.3V)
PGND to AGND....................................................-0.3V to +0.3V
PWM Current....................................................-50mA to +50mA
SMBDATA Current.............................................-1mA to +50mA
I/O1, I/O2 Current...............................................-1mA to +25mA
DXN Current......................................................................±1mA
ESD Protection (all pins, Human Body Model).................2000V
Continuous Power Dissipation (TA= +70°C)
16-Pin QSOP (derate 8.30mW/°C above +70°C).......667mW
Operating Temperature Range (extended)......-55°C to +125°C
Junction Temperature.....................................................+150°C
Storage Temperature Range............................-65°C to +150°C
Lead Temperature (soldering, 10s)................................+300°C
FAN output set to
DAC mode
FAN output set to
150Hz mode= 0°C to +100°C, diode ideality factor = 1.013
High level
PWM mode, VFANforced to 0.4V
PWM mode, VFANforced to 2.9V
Monotonicity guaranteed
VDXPforced to VDXN
+ 0.65V
SMBus static
Autoconvert mode
From stop bit to conversion complete
VCC, falling edge
VCCinput, disables A/D conversion,
rising edge
Autoconvert mode,
average measured over 1s
CONDITIONS-10FAN Output Sink Current10FAN Output Source Current0.7DXN Source Voltage100120µARemote-Diode Source Current1.622.4Conversion Rate476278Conversion Time36075150
Average Operating Supply CurrentTemperature Error, Remote Diode (Note 2)
Bits8Resolution (Note 1)
310µAStandby Supply Current50POR Threshold Hysteresis11.9 2.5Power-On Reset Threshold335.5Supply Voltage Range2.6 2.8 2.95Undervoltage Lockout Threshold50Undervoltage Lockout Hysteresis
UNITSMINTYPMAXPARAMETERSMBCLK at 10kHz3
Low level81012
ADC AND POWER SUPPLY
FAN OUTPUT
MAX1669
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
ELECTRICAL CHARACTERISTICS (continued)(VCC= +3.3V, TA
= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)
Logic Input High Voltage
PARAMETERMINTYPMAXUNITSFAN PWM Frequency Error-20+20%
FAN Total Unadjusted Error-44%FS
FAN Output Voltage High2.963.06V
CONDITIONSPWM mode, any setting
DAC mode, any setting, RL= 10kΩto GND
DAC mode, FAN duty factor = 1111b,
IOUT= 5mA
SYNC Input Low Period500ns
SYNC Input High Period500ns
SYNC Capture Range140260400kHz
2.1V
Logic Input Low Voltage0.8V
SMBDATA, ALERT, OVERT, I/O1, I/O2
Output Low Sink Current6mA
FAN Output Voltage Low0.050.2V
ALERT, OVERT, I/O1, I/O2 Output
High Leakage Current1µA
Logic Input Current-11µA
SMBus Input Capacitance5pF
SMBus Clock FrequencyDC100kHz
SMBCLK Clock Low Time (tLOW)4.7µs
SMBCLK Clock High Time (tHIGH)4µs
SMBus Rise Time1µs
SMBus Fall Time300ns
SMBus Start Condition Setup Time4.7µs
SMBus Repeated Start Condition Setup
Time (tSU:STA)500ns
SMBus Start Condition Hold Time (tHD:STA)4µs
SMBus Stop Condition Setup Time (tSU:STO)4µs
SMBus Data Valid to SMBCLK
Rising-Edge Time (tSU:DAT)250ns
Pin forced to 5.5V
Logic inputs forced to VCCor GND
ADD_, I/O1, I/O2, SYNC, SMBCLK, SMBDATA;
VCC= 3V to 5.5V
ADD_, I/O1, I/O2, SYNC, SMBCLK, SMBDATA;
VCC= 3V to 5.5V
SMBCLK, SMBDATA
(Note 3)
Pin forced to 0.4V
10% to 10% points
90% to 90% points
SMBCLK, SMBDATA, 10% to 90% points
SMBCLK, SMBDATA, 90% to 10% points
90% to 90% points
DAC mode, FAN duty factor = 0000b,
IOUT= -5mA
10% of SMBDATA to 90% of SMBCLK
90% of SMBCLK to 10% of SMBDATA
10% or 90% of SMBDATA to 10% of SMBCLK
SMBus Data-Hold Time (tHD:DAT)0µs
SMBus Bus-Free Time (tBUF)4.7µs
SMBCLK Falling Edge to SMBus
Data-Valid Time1µs
(Note 4)
Between start/stop conditions
Master clocking-in data
SMBus INTERFACE (Figures 7, 8)
Note 1:Guaranteed but not 100% tested.
Note 2:TRis the junction temperature of the remote diode. The temperature error specification is optimized to and guaranteed for a
diode-connected 2N3906 transistor with ideality factor = 1.013. Variations in the ideality factor “m” of the actual transistor
used will increase the temperature error by *. See the Temperature Error vs. Remote Diode Temperature graph in the
Typical Operating Characteristicsfor typical temperature errors using several random 2N3906s. See Remote Diode
Selectionfor remote diode forward-voltage requirements.
Note 3:The SMBus logic block is a static design that works with clock frequencies down to DC. While slow operation is possible, it
violates the 10kHz minimum clock frequency and SMBus specifications, and may monopolize the bus.
Note 4:Note that a transition must internally provide at least a hold time in order to bridge the undefined region (300ns max) of
SMBCLK’s falling edge.
Note 5:Specifications to -40°C are guaranteed by design and not production tested.
MAX1669
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
ELECTRICAL CHARACTERISTICS(VCC= +3.3V, TA
= -40°C to +85°C, unless otherwise noted.) (Note 5)Pin forced to 0.4V
ADD_, I/O1, I/O2, SYNC, SMBCLK, SMBDATA;
VCC= 3V to 5.5V
ADD_, I/O1, I/O2, SYNC, SMBCLK, SMBDATA;
VCC= 3V to 5.5V
Logic inputs forced to VCCor GND
Pin forced to 5.5V-11Logic Input Current1ALERT, OVERT, I/O1, I/O2 Output
High Leakage Current0.2FAN Output Voltage Low6SMBDATA, ALERT, OVERT, I/O1, I/O2
Output Low Sink Current0.8Logic Input Low Voltage2.1Logic Input High Voltage
DAC mode, FAN duty factor = 1111b,
IOUT= 5mA
DAC mode, any setting, RL= 10kΩto GND
PWM mode, any setting
PWM mode, VFANforced to 0.4V
PWM mode, VFANforced to 2.9V
Monotonicity guaranteed
Autoconvert mode
From stop bit to conversion complete
TR= -55°C to +125°C,diode ideality factor =1.013
Autoconvert mode, average measured over
1sec, FAN output set to 150Hz mode
CONDITIONS2.94FAN Output Voltage High
%FS-55FAN Total Unadjusted Error-25+25FAN PWM Frequency Error-10FAN Output Sink Current10FAN Output Source Current1.62.4Conversion Rate47Conversion Time100Average Operating Supply Current
Bits8Temperature Resolution (Note 1)-55Temperature Error, Remote Diode (Note 2)
UNITSMINMAXPARAMETERDAC mode, FAN duty factor =0000b,
IOUT= -5mA35.5Supply Voltage Range
ADC AND POWER SUPPLY
FAN OUTPUT
SMBus INTERFACE* . . ΔTmkTCR=−+()°()1013127315
MAX1669
Fan Controller and Remote Temperature Sensor
with SMBus Serial InterfaceTEMPERATURE ERROR
vs. LEAKAGE RESISTANCE
MAX1669-01
LEAKAGE RESISTANCE (MΩ)
TEMPERATURE ERROR (°C)
PATH = DXP TO VCC (5V); CONFIG = 02h
PATH = DXP TO GND; CONFIG = 02h
TEMPERATURE ERROR
vs. REMOTE DIODE TEMPERATURE
MAX1669-02
TEMPERATURE (°C)
TEMPERATURE ERROR (
°C)
RANDOM 2N3906s FROM
DIFFERENT MANUFACTURERS 10K100K1M10M100M
TEMPERATURE ERROR vs.
POWER-SUPPLY NOISE FREQUENCY MAX1669-03
PSNF (Hz)
TEMPERATURE ERROR (
°C)
VIN = SQUARE WAVE APPLIED TO
VCC WITH NO 0.1μF VCC CAPACITOR
VIN = 100mVp-p
VIN = 250mVp-p1G100M10M
TEMPERATURE ERROR vs.
COMMON-MODE NOISE FREQUENCYMAX1669-04
FREQUENCY (Hz)
TEMPERATURE ERROR (
°C)
VIN = 50mVp-p AC-COUPLED TO DXN
C = DXN - DXP CAPACITANCE
C = 27nF
C = 2200pF
TEMPERATURE ERROR
vs. DXP - DXN CAPACITANCE
MAX1669-05
DXP-DXN CAPACITANCE (nF)
TEMPERATURE ERROR (
°C)
VCC = 5V
STANDBY SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX1669-06
SUPPLY VOLTAGE (V)
STANDBY SUPPLY CURRENT (
RESPONSE TO THERMAL SHOCK
MAX1669-07
TIME (sec)
TEMPERATURE (
°C)
CMPT3906 IMMERSED IN
+115°C FLUORINERT BATH0
PWM FREQUENCY vs. CODE (F3F2F1F0)
MAX1669-08
CODE (F3F2F1F0)
PWM FREQUENCY (Hz)
VCC = +3.3V
VCC = +5V
Typical Operating Characteristics(Temperature error = measured - actual, TA= +25°C, unless otherwise noted.)
MAX1669
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
Typical Operating Characteristics (continued)(Temperature error = measured - actual, TA= +25°C, unless otherwise noted.)
Pin DescriptionPWM DUTY FACTOR vs. CODE (D3D2D1D0)
MAX1669-09
CODE (D3D2D1D0)
DUTY FACTOR (%)
VCC = +3.3V OR +5V
DAC OUTPUT vs. CODE (D3D2D1D0)
MAX1669-10
CODE (D3D2D1D0)
DAC OUTPUT (V)
ILOAD = +10mA TO -10mA
VCC = +5V
NAMEFUNCTIONI/O1General-Purpose Open-Drain Logic Input/Output 1. I/O1 is intended for driving LEDs, driving power-plane
switching MOSFETs, or detecting fan presence or chassis intrusion.I/O2General-Purpose Open-Drain Logic Input/Output 2. I/O2 is intended for driving LEDs, driving power-plane
switching MOSFETs, or detecting fan presence or chassis intrusion.
PINADD0SMBus Address Select Pin 0. See Table 11.ADD1SMBus Address Select Pin 1. See Table 11.DXPCombined Current Source and ADC Positive Input from Remote Diode. Place a 2200pF capacitor
between DXP and DXN for noise filtering.DXNCombined Current Sink and ADC Negative Input from Remote Diode. DXN is normally biased to a diode
voltage above ground. AGNDAnalog GroundADD2SMBus Address Select Pin 2. See Table 11.SMBCLKSMBus Serial-Clock InputPGNDPower GroundFANFan-Control Logic Output. Swings from PGND to VCCin PWM mode, or PGND to 0.94 ·VCCin DAC mode.SYNC
Oscillator Synchronization Input. Connect to AGND to use internal clock. Capture range is 140kHz to
400kHz. The synchronization signal is internally applied to the FAN PWM clock. See Table 5 for synchro-
nized frequencies.VCCSupply Voltage Input, +3V to +5.5V. Bypass to AGND with a 0.1µF capacitor. OVERTActive-Low, Open-Drain Thermostat Output. Activated by TCRITthresholdALERTActive-Low, Open-Drain SMBus Alert (interrupt) OutputSMBDATAOpen-Drain SMBus Serial-Data Input/Output
MAX1669
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
_______________Detailed DescriptionThe MAX1669 temperature sensor is designed to work
with an external microcontroller (µC) or other intelligent
devices in computer fan-control applications. The µC is
typically a power-management or keyboard controller,
generating SMBus serial commands by “bit-banging’’
general-purpose input/output (GPIO) pins or through a
dedicated SMBus interface block.
Essentially an 8-bit serial analog-to-digital converter
(ADC) with a sophisticated front end, the temperature
measurement channel contains a switched-current
source, a multiplexer, and an integrating ADC.
Temperature data from the ADC is loaded into a data
register, where it is automatically compared with data
previously stored in over/undertemperature alarm regis-
ters and the critical register (Figure 1).
MUXREMOTE-TEMPERATURE
DATA REGISTER
HIGH-TEMPERATURE
THRESHOLD
LOW-TEMPERATURE
THRESHOLD
DIGITAL COMPARATOR
TEMPERATURE
TEMPERATURE SENSOR
TCRIT
COMMAND-BYTE
(INDEX) REGISTER
SMBDATA
SMBCLK
ADDRESS
DECODERREADWRITE
CONTROL
LOGIC
CONTROL
LOGIC
SMBADD2
ADD1
ADD0
STATUS BYTE REGISTER
CONFIGURATION
BYTE REGISTER
ALERT RESPONSE
ADDRESS REGISTER
ADCDXP
DXN
GND
VCC
ALERT
MAX1669
CONTROL
LOGICOVERT
GENERAL-PURPOSE
I/O CONTROLLER
-5°C
I/O1
I/O2
Figure 1. MAX1669 Temperature Sensor Functional Diagram
MAX1669
Fan Controller and Remote Temperature Sensor
with SMBus Serial InterfaceThe PWM or DAC fan control circuitry is completely
independent from the temperature measurement, and
software closes the temperature-control feedback loop
(Figure 2).
ADC and MultiplexerThe ADC is an averaging type that integrates over a
62ms period (typ), with excellent noise rejection. The
multiplexer automatically steers bias currents through
the remote diode, measures the forward voltage, and
calculates the temperature.
The DXN input is biased at 0.7V above ground by an
internal diode to set up the analog-to-digital (A/D)
inputs for a differential measurement. The worst-case
DXP-DXN differential input voltage range is 0.21V to
0.95V. Diode voltages that are outside the ADC input
range cause overrange indications rather than non-
monotonic readings. Overrange readings will return
+127°C. Excess resistance in series with the remote
diode causes approximately +1/2°C error/Ω. Likewise,
200µV of offset voltage forced on DXP-DXN causes
approximately +1°C error.
A/D Conversion SequenceWhen the device is taken out of standby mode, the
result of the measurement is available one conversion
time later (78ms max). If the ADC is busy, the results of
the previous conversion are always available. Toggling
the standby mode on and off is a good way to initiate a
new conversion since this action resets the rate timer.
Low-Power Standby ModeSupply-current drain during the 62ms conversion peri-
od is 500µA. Between conversions, the instantaneous
supply current is 18µA. In standby mode, supply cur-
rent drops to 3µA and the fan output is disabled.
SMBus Digital InterfaceFrom a software perspective, the MAX1669 appears as
a set of byte-wide registers that contain temperature
data, alarm threshold values, or control bits. A standard
SMBus 2-wire serial interface is used to read tempera-
ture data and write control bits and alarm threshold
data.
The MAX1669 employs four standard SMBus protocols:
write byte, read byte, send byte, and receive byte
(Figure 3). The two shorter protocols (receive and
send) allow quicker transfers, provided that the correct
data register was previously selected by a write or read
byte instruction. Use caution with the shorter protocols
in multimaster systems since a second master could
overwrite the command byte without informing the first
master.
The temperature data format is 7 bits plus sign in two’s
complement form for each channel, with the LSB repre-
senting +1°C (Table 1), MSB transmitted first.
Measurements are offset by +1/2°C to minimize internal
rounding errors; for example, +99.5°C to +100.4°C is
reported as +100°C.
Alarm Threshold RegistersThree registers store alarm threshold data, with high-
temperature (THIGH) and low-temperature (TLOW) reg-
isters that activate the ALERToutput, and a critical
overtemperature register (TCRIT) that activates the
OVERToutput. If a measured temperature equals or
exceeds the THIGHor TLOWthreshold value, an ALERT
interrupt is asserted. Do not set the TCRITregister to
values outside of the temperatures in Table 1.
The power-on-reset (POR) state of the THIGHregister is
full scale (0111 1111b or +127°C). The POR state of the
TLOWregister is 1100 1001b or -55°C. The POR state of
the TCRITregister is 0110 0100b or +100°C.
OVERT Thermostat OutputThe OVERToutput is a self-clearing interrupt output
that is activated when the temperature equals or
exceeds TCRIT. OVERTnormally goes low when active,
but this polarity can be changed through the configura-
tion register. The latch is cleared when the temperature
reading is equal to or less than TCRITminus 5°C, which
provides for 5°C of hysteresis.
The ALERTand OVERTcomparisons are made after
each conversion, and at the end of a write command to
their respective temperature limit registers. For exam-
ple, if the limit is changed while the device is in standby
OVERT
FANON
FAN
DAC
PWM
CONTROLLER
DRIVER
CONTROL
LOGIC
(0XF0)
UPPER NIBBLE
FREQ
REGISTER
MUX
AND
MAX1669
DUTY
REGISTER
Figure 2. MAX1669 Fan-Control Functional Diagram
MAX1669
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interfacemode, the ALERTand OVERToutputs respond correct-
ly according to the last valid A/D result.
Note that the ALERToutput does not respond to TCRIT
(OVERT) comparisons.
The OVERTlatch can implement an override control to
the FAN output, which forces the fan to VCC whenever
the TCRIT threshold is crossed. This override switch is
the backup fan control loop, and is enabled through the
FAN ON bit in the configuration register (bit 2). Note
that changing the duty to 100% in this way doesn’t
affect the contents of the DUTY register, and the FAN
output reverts to the preprogrammed duty factor (or
DAC voltage) when the OVERTlatch is reset.
Diode Fault AlarmA continuity fault detector at DXP detects whether the
remote diode has an open-circuit condition, short-cir-
cuit to GND, or short-circuit DXP-to-DXN condition. At
the beginning of each conversion, the diode fault is
checked and the status byte updated. This fault detec-
tor is a simple voltage detector; DXP rising above VCC-
1V or falling below DXN + 40mV constitutes a fault con-
dition. Also, if the ADC has an extremely low differential
input voltage, the diode is assumed to be shorted and
a fault occurs. Note that the diode fault isn’t checked
until a conversion is initiated, so immediately after
power-on reset the status byte indicates no fault is pre-
sent even if the diode path is broken. Any diode fault
will return a +127°C fault reading and cause ALERTto
go low.
Write Byte Format
Read Byte Format7-bit slave address:
equivalent to chip-select line
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:
equivalent 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
S = Start conditionShaded = Slave transmission
P = Stop conditionA= Not acknowledged
Figure 3. SMBus Protocols
ACK
COMMAND8 bits
ACK
ADDRESS7 bits
ACK
DATA8 bits
ADDRESS7 bits1
ACK8 bits
COMMANDACK8 bits
DATAACK1
TEMP (°C)ROUNDED
TEMP (°C)+0.25+0
+0.50+1
+25.25+25
+126.00+126
+0.00+0
-0.25+0
-0.50+0
+127.00
+130.00+127
+127
+126.50+127
DIGITAL OUTPUT
DATA BITS
SIGN MSBsLSBs
1 11111110000000
1 11001110000001
0 0011001
0 1111110
0 0000000
0 0000000
1 1100110
1 1001001
0 0000000
1 1111111100100101111110111111 1111111
0 1111111
0 1111111
Table 1. Data Format (Two’s Complement)
ADDRESS7 bits
MAX1669
Fan Controller and Remote Temperature Sensor
with SMBus Serial Interface
ALERTInterruptsThe ALERTinterrupt output signal is latched and can
only be cleared by reading the Alert Response
address. Interrupts are generated in response to THIGH
and TLOWcomparisons, when there is a fault with the
remote diode, or when a high-to-low or low-to-high tran-
sition at I/O1 or I/O2 is detected.
The interrupt does not halt automatic conversions; new
temperature data continues to be available over the
SMBus interface after ALERTis asserted. The interrupt
output is open-drain so that devices can share a com-
mon interrupt line. The interface responds to the SMBus
Alert Response address, an interrupt pointer return-
address feature (see the AlertResponse Addresssec-
tion).
The ALERTinterrupt latch is set when the temperature
exceeds an ALARM threshold. ALERTwill not be set
again until the threshold is reprogrammed. This pre-
vents the ALERTlatch from being set again during the
interval between reading the Alert Response address
and updating the offending alarm threshold. Note that
this behavior is identical to the MAX1618 but is slightly
different from the MAX1617, which continues to inter-
rupt until the temperature no longer exceeds the alarm
threshold. Note also that if some new alarm condition
occurs, such as crossing the other alarm threshold or
having a GPIO transition, a new interrupt is generated.
ALERT Response AddressThe SMBus Alert Response interrupt pointer provides
quick fault identification for simple slave devices that
lack the complex, expensive logic needed to be a bus
master. Upon receiving an ALERTinterrupt signal, the
host master can broadcast a receive byte transmission
to the Alert Response slave address (0001100b). Then
any slave device that generated an interrupt attempts
to identify itself by putting its own address on the bus
(Table 2).
The Alert Response can activate several different slave
devices simultaneously, similar to the I2C General Call.
If more than one slave attempts to respond, bus arbitra-
tion rules apply, and the device with the lower address
code wins. The losing device does not generate an
acknowledge and continues to hold the ALERTline low
until serviced. Successful reading of the alert response
address clears the interrupt latch.
Command Byte FunctionsThe 8-bit command byte register (Table 3) is the master
index that points to the MAX1669’s other registers. The
register’s POR state is 00000001b, so a receive byte
transmission (a protocol that lacks the command byte)
that occurs immediately after POR returns the current
remote temperature data.
One-Shot ConversionThe one-shot command immediately forces a new con-
version cycle to begin. In software standby mode
(STBY bit = 1), a new conversion starts, after which the
device returns to standby mode. If a conversion is in
progress when a one-shot command is received, the
command is ignored. If a one-shot command is
received in autoconvert mode (STBY bit = 0) between
conversions, a new conversion begins, the conversion
rate timer is reset, and the next automatic conversion
takes place after a full period.
Configuration Byte FunctionsThe configuration byte register (Table 4) is used to
mask (disable) interrupts, set the OVERToutput polari-
ty, and put the device in software standby mode. Bit 1
of the configuration byte in Table 4 is for factory use
only and must be set to 1 (value at POR). This register’s
contents can be read back over the serial interface.
FAN PWM Frequency and
Duty Factor ControlThe fan speed is controlled by the average voltage
applied to the fan. The average voltage is equal to the
product of the motor power-supply voltage and the
duty factor. The duty factor is equal to zero upon start-
up and it is software controlled. The FAN output fre-
quency is controlled by the PWM frequency register
unless this register’s code is set to 1111b (Table 5). A
PWM frequency code of 1111b puts the FAN output in
DAC mode. For all other codes, the FAN frequency is in
the 20Hz to 160Hz range as shown in Table 5. For the
possible synchronized frequencies, also see Table 5.
The FAN output duty factor is controlled by the FAN
duty factor register unless the PWM frequency code is
BITNAMEADD1ADD2ADD3ADD4
0 (LSB)1
7 (MSB)ADD7
ADD6ADD5
FUNCTIONLogic 1
Provide the MAX1669
slave address
Table 2. Read Format for the Alert
Response Address (0001100b)
