EMC2302 Standard Microsystems Corp., EMC2302 Datasheet - Page 16

• Manufacturer Part Number: EMC2302
• Description: Rpm-based Pwm Fan Controller
• Manufacturer: Standard Microsystems Corp.

Chapter 4 Product Description
Revision 1.2 (03-22-10)
4.1
MCU
The EMC2302 is an SMBus compliant fan controller with two programmable frequency PWM fan
drivers. The fan drivers can be operated using two modes: the RPM-based Fan Speed Control
Algorithm or the direct fan drive setting.
Figure 4.1
The EMC2302 has two modes of operation for each fan driver. Each mode of operation uses the Ramp
Rate control and Spin Up Routine.
1. Direct Setting Mode - in this mode of operation, the user directly controls the fan drive setting.
2. Fan Speed Control Mode (FSC) - in this mode of operation, the user determines a target
Fan Control Modes of Operation
Updating the Fan Driver Setting Register (see
Ramp Rate control is optional and enabled via the EN_RRC bits.
tachometer count and the PWM drive setting is automatically updated to achieve this target speed.
The algorithm uses the Spin Up Routine and has user definable ramp rate controls.
32.768KHz Clock
Input or Output
Whenever the Direct Setting Mode is enabled, the current drive will be changed to what was
last written into the Fan Driver Setting Register.
This mode is enabled setting the EN_ALGO bit in the Fan Configuration Register.
shows a system diagram of the EMC2302.
Figure 4.1 System Diagram of EMC2302
SMCLK
SMDATA
ALERT#
CLK
DATASHEET
EMC2302
VDD
16
3.3V
Section
TACH2
TACH1
PWM2
PWM1
GND
5.7) will instantly update the PWM fan drive.
Dual RPM-Based PWM Fan Controller
Circuit
Circuit
Drive
Drive
tachometer
tachometer
SMSC EMC2302
Datasheet