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.
shows a system diagram of the EMC2104.
3.3V
3.3V
3.3V
VDD
SMCLK
TACH1
tachometer
KBC
SMDATA
PWM1
ALERT#
3.3V
Drive
Circuit
CPU
Thermal
diode
DP1*
DN1*
EMC2104
TACH2*
PWM2*
0.8V
tachometer
3.3V
Drive
Circuit
GPU
Thermal
diode
DP2*
DN2*
1.2k
SYS_SHDN#
SHDN_SEL
TRIP_SET*
APD
(optional)
32.768KHz Clock
CLK_IN*
DP3 / DN4*
DN3 / DP4*
Figure 5.1 System Diagram of EMC2104
SMSC EMC2104
21
Revision 1.74 (05-08-08)
DATASHEET
SMSC [ SMSC CORPORATION ]
