This product can monitor temperature and automatically adjust fan speed to ensure optimum cooling while minimizing acoustic noise from the fan.
The MAX6643, MAX6644 and MAX6645 are automatic PWM fan‑speed controllers that monitor temperature and adjust fan speed to provide optimal cooling while minimizing acoustic noise. Each device measures two temperature locations and generates a PWM waveform to drive an external power transistor. The MAX6643 monitors its own die temperature and an optional external transistor, while the MAX6644 and MAX6645 monitor one or two external diode‑connected transistors.
Key features include selectable high‑ and low‑temperature trip points, an overtemperature (OT) output for warning or shutdown, a FANFAIL output for fan‑failure detection, and a FULLSPD input that forces the PWM duty cycle to 100 %. The devices operate from 3.0 V to 5.5 V, are available in 16‑pin QSOP (MAX6643/4) or 10‑pin UMAX (MAX6645) packages, and support a 32 Hz PWM output frequency.
| Operating Supply Voltage Range | 3.0 V to 5.5 V |
|---|---|
| Operating Temperature Range | -40 °C to +125 °C |
| PWM Output Frequency | 32 Hz |
| Fan‑Fail Minimum Tachometer Frequency | 16 Hz |
| Average Operating Current (50 % duty, no load) | 0.5 mA |
| Package Types | 16‑Pin QSOP (MAX6643/4) / 10‑Pin UMAX (MAX6645) |
The PWM output operates at a fixed frequency of 32 Hz.
The MAX6643 monitors its own die temperature and an optional external transistor temperature.
Pulling the FULLSPD input high forces the PWM output to a 100 % duty cycle.