RPM-Based Fan Controller with HW Thermal Shutdown
Datasheet
Chapter 5 General Description
The EMC2103 is an SMBus compliant fan controller with one external (EMC2103-2 offers up to three
external diode channels) and one internal temperature channels. The fan driver 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 of the BJT or transistor model for a CPU diode).
The EMC2103 allows the user to program temperatures generated from external sources to control
the fan speed. This functionality also supports DTS data from the CPU. By pushing DTS or standard
temperature values into dedicated registers, the external temperature readings can be used in
conjunction with the external diode(s) and internal diode to control the fan speed.
The EMC2103 also includes a hardware programmable temperature limit and dedicated system
shutdown output for thermal protection of critical circuitry.
Figure 5.1 shows a system diagram of the EMC2103.
* denotes EMC2103-2 only
VDD VDD
EMC2103
HOST
CPU
SMCLK
DP1
DN1
SMBus
Interface
SMDATA
Thermal
diode
VDD
ALERT
GPIO1*
GPIO2*
DP2 / DN3*
DN2 / DP3*
1.5V
Optional anti-
parallel diode
PWM
Fan Drive
Circuitry
1.2k
TACH
TRIP_SET
VDD
SYS_SHDN
Figure 5.1 System Diagram for EMC2103
Revision 0.85 (01-29-08)
SMSC EMC2103
DATA2S0HEET
SMSC [ SMSC CORPORATION ]
