EMC2301 Standard Microsystems Corp., EMC2301 Datasheet - Page 16

• Manufacturer Part Number: EMC2301
• Description: Rpm-based Pwm Fan Controller
• Manufacturer: Standard Microsystems Corp.

Chapter 4 Product Description
Revision 1.2 (03-22-10)
4.1
Fan Driver Setting (read / write)
EDGES[1:0]
MCU
The EMC2301 is an SMBus compliant fan controller with a programmable frequency PWM fan driver.
The fan driver can be operated using two modes: the RPM-based Fan Speed Control Algorithm or the
direct fan drive setting.
Figure 4.1
The EMC2301 has two modes of operation for the 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
DIRECT SETTING MODE
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
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.
Input or Output
shows a system diagram of the EMC2301.
Table 4.1 Fan Controls Active for Operating Mode
Figure 4.1 System Diagram of EMC2301
SMCLK
SMDATA
ALERT#
CLK
DATASHEET
EMC2301
VDD
16
3.3V
Fan Driver Setting (read only)
EDGES[1:0]
(Fan Configuration)
Section
TACH
PWM
GND
5.7) will instantly update the PWM fan drive.
FSC MODE
RPM-Based PWM Fan Controller
Circuit
Drive
tachometer
SMSC EMC2301
Datasheet