1°C Temperature Sensor with Beta Compensation
Datasheet
Chapter 5 Product Description
The EMC1403 and EMC1404 are SMBus temperature sensors. The EMC1403 monitors one internal
diode and two externally connected temperature diodes. The EMC1404 monitors one internal diode
and three externally connected temperature diodes.
Thermal management is performed in cooperation with a host device. This consists of the host reading
the temperature data of both the external and internal temperature diodes of the EMC1403 and
EMC1404 and using that data to control the speed of one or more fans.
The EMC1403 and EMC1404 have two levels of monitoring. The first provides a maskable ALERT
signal to the host when the measured temperatures exceeds user programmable limits. This allows
the EMC1403 or EMC1404 to be used as an independent thermal watchdog to warn the host of
temperature hot spots without direct control by the host. The second level of monitoring provides a non
maskable interrupt on the THERM pin if the measured temperatures meet or exceed a second
programmable limit.
Since the EMC1403 and EMC1404 automatically correct for temperature errors due to series
resistance in temperature diode lines, there is greater flexibility in where external diodes are positioned
and better measurement accuracy than previously available with non-resistance error correcting
devices. The automatic beta detection feature means that there is no need to program the device
according to which type of diode is present on the External Diode 1 channel. This also includes CPU
diodes that require the transistor or BJT model for monitoring their temperature. Therefore, the
EMC1403/EMC1404 can power up ready to operate for any system configuration.
For the EMC1404, External Diode channels 2 and 3 are only compatible with general purpose diodes
(such as a 2N3904).
Figure 5.1 shows a system level block diagram of the EMC1403. Figure 5.2 shows a system level block
diagram of the EMC1404.
EMC1403
CPU
Host
DP1
DN1
Thermal
diode
SMCLK
Internal
Diode
SMDATA
SMBus
Interface
ALERT
DP2
DN2
THERM
Power Control
Figure 5.1 System Diagram for EMC1403
SMSC EMC1403/EMC1404
Revision 2.0 (08-10-12)
DATA1S7HEET
SMSC [ SMSC CORPORATION ]
