The MAX6684 is an integrated fan-failure detector that detects when a fan exhibits excessive underspeed or a locked rotor. This device is especially well suited for critical systems where no fan control, or simple on/off control is desired. The MAX6684 detects fan failure by evaluating fluctuations in current at the low side of the fan; no tachometer signal is necessary. The output of the device, FAIL, is an active-low, open-drain alarm. The MAX6684 can also be used to switch the fan on or off, based on the state of a logic-level input, OFF. This device can be used with fans rated at up to 24V and 250mA. The MAX6684 is available in an 8-pin SO package, and is specified for operation from -40°C to +85°C.
The MAX6684 fan‑failure detector monitors low‑side fan current to detect underspeed, locked‑rotor, over‑current, and thermal‑shutdown conditions. It provides an active‑low FAIL output and an OFF pin that can switch the fan on or off based on a logic‑level input.
The device is supplied in an 8‑pin SO package, operates from –40 °C to +85 °C, and is compatible with ordinary 2‑wire fans rated up to 24 V and 250 mA. Detailed electrical characteristics, pin functions, and application circuits are included in the datasheet.
| Supply Voltage (VCC) | 3.0 V to 5.5 V |
|---|---|
| Supply Current (I_CC) at IFAN = 300 mA | 3.4 mA |
| Operating Temperature Range | -40 °C to +85 °C |
| Maximum Fan Voltage | 24 V |
| Maximum Fan Current | 250 mA |
| FAIL Output Type | Active‑low open‑drain alarm |
The FAIL pin provides an active‑low, open‑drain alarm signal.
The MAX6684 can be used with fans up to 24 V and 250 mA.
It is specified for operation from –40 °C to +85 °C.
It monitors fluctuations in low‑side fan current; a low AC component or low frequency indicates failure.