EMC2303(2009) Datasheet - SMSC -> Microchip

General Description
   The EMC2303 is an SMBus compliant fan controller with up to three independently controlled PWM fan drivers. Each fan driver is controlled by a programmable frequency PWM driver and Fan Speed Control algorithm that operates in either a closed loop fashion or as a directly PWM-controlled device.

FEATUREs
◾ Three Programmable Fan Control circuits (EMC2303)
   — 4-wire fan compatible
   — High speed PWM (26 kHz)
   — Low speed PWM (9.5Hz - 2240 Hz)
   — Optional detection of aging fans
   — Fan Spin Up Control and Ramp Rate Control
   — Alert on Fan Stall
   — Up to 3 Selectable Default Fan Speeds
◾ Watchdog Timer
◾ RPM-based fan control algorithm
   — 0.5% accuracy from 500 RPM to 16k RPM (external
      crystal oscillator)
   — 1% accuracy from 500 RPM to 16k RPM (internal clock)
◾ SMBus 2.0 Compliant
   — Up to 6 selectable SMBus addresses
   — SMBus Alert compatible
◾ CLK Pin can provide a clock source output
◾ Available in a 12-pin 4mm x 4mm QFN Lead-free
   RoHS Compliant package

APPLICATIONs
◾ Servers
◾ Projectors
◾ Industrial and Networking Equipment
◾ Notebook Computers