View max6660 datasheet:

19-2225; Rev 0; 10/01 Remote-Junction Temperature-Controlled Fan-Speed Regulator with SMBus Interface General Description Features The MAX6660 is a remote temperature sensor and fan- ¦ Integrated Thermal Sensing and Fan-Regulation speed regulator that provides a complete fan-control Solution solution. The remote temperature sensor is typically a ¦ Programmable Fan Threshold Temperature common-collector PNP, such as a substrate PNP of a microprocessor, or a diode-connected transistor, typi- ¦ Programmable Temperature Range for Full-Scale cally a low-cost, easily mounted 2N3904 NPN type or Fan Speed 2N3906 PNP type. ¦ Accurate Closed-Loop Fan-Speed Regulation The device also incorporates a closed-loop fan con- troller that regulates fan speed with tachometer feed- ¦ On-C