MAX6650/MAX6651 are fan controllers for 5VDC/12VDC brushless fans with built-in tachometers. They support SMBus™/I2C* interface, can monitor fan speed and automatically adjust voltage to match the pre-programmed speed.
The MAX6650 and MAX6651 fan controllers use a 2‑wire SMBus/I²C‑compatible interface to regulate and monitor the speed of 5 VDC/12 VDC brushless fans with built‑in tachometers. They adjust fan voltage via an external MOSFET or bipolar transistor, forcing the tachometer frequency to match a programmed value.
Both devices provide general‑purpose I/O pins, selectable slave addresses, and optional hardware full‑on override. The MAX6650 supports a single fan, while the MAX6651 can monitor up to four fans and control them as a unit. Packages are a 10‑pin UMAX for the MAX6650 and a 16‑pin QSOP for the MAX6651.
| Supply Voltage (Vcc) | 3.0 V to 5.5 V |
|---|---|
| Supply Current (Full‑on mode) | 10 mA |
| Output Sink Current | 10 mA |
| Output Source Current | 50 mA |
| Operating Temperature Range | -40 °C to +85 °C |
| GPIO Sink Capability | 10 mA |
| Package Types | 10‑pin UMAX (MAX6650) / 16‑pin QSOP (MAX6651) |
They use a 2‑wire SMBus/I²C‑compatible interface for register access.
The MAX6651 can monitor up to four fans using its additional tachometer inputs.
Slave addresses are set by strapping the ADD pins, providing four selectable addresses.
The allowed supply voltage range is 3.0 V to 5.5 V.