MAX6668

19-2133; Rev 2; 11/02 Remote Temperature Switches with Integrated Fan Controller/Driver General Description The MAX6668/MAX6670 remote-junction thermal switches with an internal power transistor drive a cooling fan rated for supply voltages up to +12V and 250mA. These devices measure the temperature of an external P-N junction (typically a diode-connected transistor) and turn on the fan power switch when the remote temperature rises above a factory-programmed threshold. Self-contained and requiring no software development, the MAX6668/MAX6670 are simple “drop-in” fan-control solutions for a variety of systems. The MAX6670 features an open-drain WARN output that goes active when the remote temperature exceeds the factory-programmed fan activation threshold by +15°C. The MAX6670 features an open-drain OT output that goes active when the remote temperature exceeds the factory-programmed threshold by +30°C. The MAX6668/MAX6670 provide a fan-control input, FORCEON, that allows the fan to be driven externally, regardless of temperature. Available temperature thresholds range from +40°C to +75°C in 5°C increments. Hysteresis is preset to 8°C on the MAX6668 or pin selectable to 4°C, 8°C, or 12°C using a three-level logic input on the MAX6670. Temperature threshold accuracy is ±1°C (typ) and ±2.2°C (max) for remote-junction temperatures from +40°C to +75°C. The MAX6668/MAX6670 operate from a +3V to +3.6V power supply, and are specified over the automotive temperature range (-40°C to ...