The MAX1669 fan controller includes a precise digital thermometer that reports the temperature of a remote sensor. The remote sensor is a diode-connected transistor-typically a low-cost, easily mounted 2N3906 PNP type-replacing conventional thermistors or thermocouples. Remote accuracy is ±3°C for transistors from multiple manufacturers, with no calibration needed. The MAX1669 has an independent fan controller with a low-current logic output requiring external power components 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/outputs (GPIOs) for fan presence detection and a thermostat output intended as a fan override signal in case the host system loses the ability to communicate. The internal 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.
Key Features
Applications/Uses
Measures Remote CPU Temperature
No Calibration Required
20Hz to 160Hz PWM Output for Fan
PWM Frequency Sync Input (260kHz)
Flexible Fan Interface: Linear or PWM
SMBus 2-Wire Serial Interface
Programmable Under/Overtemperature Alarms
ALERT-bar Latched Interrupt Output
OVERT-bar Thermostat Output
Two GPIO Pins
Write-Once Configuration Protection
Supports SMBus Alert Response
±3°C Temperature Accuracy (-40°C to +125°C, remote)
3µA Standby Supply Current
+3V to +5.5V Supply Range
Small 16-Pin QSOP Package
Remote diode sensor, PWM and linear fan control, dual alarms
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