The MAX6639 is a temperature monitor that monitors its own temperature and the temperature of an external diode-connected transistor or two external diode-connected transistors typically found in CPUs, FPGAs, or GPUs. It features a 2-wire serial interface that accepts SMBus commands for reading temperature data and setting alarm thresholds. Temperature data can be read at any time over the SMBus, and three programmable alarm outputs can be used for generating interrupts, throttle 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, providing minimum noise when the system is running cool and maximum cooling when power dissipation increases. Speed control is achieved through tachometer feedback from the fan, ensuring control of the fan speed rather than just the PWM duty cycle. The speed measurement accuracy is ±4%. The MAX6639 is available in 16-pin QSOP and 16-pin thin QFN 5mm x 5mm packages. It operates from 3.0V to 3.6V and consumes just 500µA of supply current. It is suitable for applications such as desktop computers, notebook computers, projectors, servers, and networking equipment.
The MAX6639 and MAX6639F are 2‑channel temperature monitors that can sense their own die temperature and up to two external diode‑connected transistors, typically found in CPUs, FPGAs or GPUs. The devices include an internal dual‑PWM fan‑speed controller that adjusts up to two cooling fans based on temperature readings, providing quiet operation at low load and maximum cooling when needed. Applications include desktop and notebook computers, projectors, servers and networking equipment.
Key features include a standard 2‑wire SMBus interface, three programmable alarm outputs (OT, THERM, ALERT), two open‑drain PWM fan outputs that can be pulled up to +13.5 V, and accurate fan‑speed measurement (±3 %). The datasheet provides absolute maximum ratings, electrical characteristics, pin descriptions, timing diagrams and typical operating curves for both the MAX6639 and the MAX6639F variant.
| Operating Supply Voltage Range | 3.0 V to 3.6 V |
|---|---|
| Standby Current | 3 µA |
| Operating Current (ADC active) | 0.5 mA to 1 mA |
| Remote Temperature Accuracy | ±1 °C |
| Fan‑Speed Measurement Accuracy | ±3 % |
| PWM Output Frequency | Up to 25 kHz |
| Number of PWM Fan Outputs | 2 (open‑drain, pull‑up to +13.5 V) |
| Package Types | 16‑pin QSOP, 16‑pin thin QFN 5 mm × 5 mm |
| Maximum Pull‑up Voltage for Fan Outputs | +13.5 V |
It uses a standard 2‑wire SMBus compatible serial interface for register read/write operations.
The device provides two open‑drain PWM fan outputs that can be pulled up to +13.5 V.
The standby current is 3 µA.
It can measure temperatures from –40 °C up to +150 °C.