EMC1424 SMSC Corporation, EMC1424 Datasheet - Page 16

• Manufacturer Part Number: EMC1424
• Description: (EMC1423 / EMC1424) Temperature Sensor
• Manufacturer: SMSC Corporation

Chapter 5 Product Description
Revision 1.16 (03-15-07)
Thermal
diode
CPU
The EMC1423 and EMC1424 are SMBus temperature sensors with Hardware Thermal Shutdown. The
EMC1423 monitors one internal diode and two externally connected temperature diodes. The
EMC1424 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 EMC1423 and
EMC1424 and using that data to control the speed of one or more fans.
The EMC1423 and EMC1424 have two levels of monitoring. The first provides a maskable ALERT
signal to the host when measured temperatures meet or exceed user programmable limits. This allows
the EMC1423 or EMC1424 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 asserts the SYS_SHDN pin when the External Diode 1 temperature
exceeds a hardware specified threshold temperature. Additionally, the internal diode and External
Diode 2, and External Diode 3 (EMC1424 only) can be configured to assert the SYS_SHDN pin when
the measured temperature exceeds user programmable limits.
Since the EMC1423 and EMC1424 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. Therefore, the
EMC1423/EMC1424 can power up ready to operate for any system configuration.
For the EMC1424, External Diode channels 2 and 3 are only compatible with general purpose diodes
(such as a 2N3904).
Figure 5.1
diagram of the EMC1424.
shows a system level block diagram of the EMC1423.
Figure 5.1 System Diagram for EMC1423
DN2
DN1
DP2
EMC1423
DP1
Internal
Diode
DATASHEET
SYS_SHDN
SMCLK
SMDATA
ALERT
16
1°C Temperature Sensor with Hardware Thermal Shutdown
Interface
Power Control
SMBus
Host
Figure 5.2
shows a system level block
SMSC EMC1423/EMC1424
Datasheet