View max6668 datasheet:

19-2133; Rev 0; 8/01 Remote Temperature Switches with Integrated Fan Controller/Driver General Description Features The MAX6668/MAX6670 remote-junction thermal ¦ +12V, 250mA Integrated Fan Driver switches with an internal power transistor drive a cool- ¦ No Calibration Required ing fan rated for supply voltages up to +12V and 250mA. These devices measure the temperature of an ¦ Pin-Selectable 4°C, 8°C, or 12°C Hysteresis external P-N junction (typically a diode-connected tran- (MAX6670) sistor) and turn on the fan power switch when the ¦ Factory-Programmed Temperature Thresholds remote temperature rises above a factory-programmed threshold. Self-contained and requiring no software from +40°C to +75°C development, the MAX6668/MAX6670 are simple ¦ Overtemperature Warning Si