Dual RPM-Based PWM Fan Controller with Hardware Thermal Shutdown
Datasheet
Chapter 5 Product Description
The EMC2104 is an SMBus compliant fan controller with up to five (up to 4 external and 1 internal)
temperature channels. It contains two fan drivers, both PWM outputs with programmable frequencies.
The fan drivers can be operated using two methods each with two modes. The methods include an
RPM based Fan Speed Control Algorithm and a direct PWM drive setting. The modes include manually
programming the desired settings or using the internal programmable temperature look-up table to
select the desired setting based on measured temperature.
The temperature monitors offer 1°C accuracy (for external diodes) with sophisticated features to
reduce errors introduced by series resistance and beta variation of substrate thermal diode transistors
commonly found in processors (including support for BJT or transistor model for CPU diodes).
The EMC2104 also includes a hardware programmable temperature limit and dedicated system
shutdown output for thermal protection of critical circuitry. Any of the three temperature channels can
be configured to measure a thermistor or voltage channel using a precision reference voltage for
reduced system complexity.
Figure 5.1 shows a system diagram of the EMC2104.
3.3V
3.3V
3.3V
3.3V
VDD
tachometer
TACH1
PWM1
SMCLK
SMDATA
ALERT#
KBC
Drive
Circuit
CPU
EMC2104
tachometer
DP1*
DN1*
Thermal
diode
TACH2*
PWM2*
Drive
Circuit
3.3V
0.8V
GPU
DP2*
DN2*
Thermal
diode
SYS_SHDN#
SHDN_SEL
1.2k
APD
(optional)
TRIP_SET*
CLK_IN*
32.768KHz Clock
DP3 / DN4*
DN3 / DP4*
Figure 5.1 System Diagram of EMC2104
SMSC EMC2104
Revision 1.74 (05-08-08)
DATA2S1HEET
SMSC [ SMSC CORPORATION ]
