EMC1422 SMSC Corporation, EMC1422 Datasheet - Page 15

• Manufacturer Part Number: EMC1422
• Description: 1C Temperature Sensor
• Manufacturer: SMSC Corporation

1°C Temperature Sensor with Hardware Thermal Shutdown
Datasheet
Chapter 5 Product Description
SMSC EMC1422
5.0.1
5.0.2
Thermal
diode
CPU
The EMC1422 is an SMBus temperature sensor with Hardware Thermal Shutdown. The EMC1422
monitors one internal diode and one externally connected temperature diode.
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 EMC1422 and using
that data to control the speed of one or more fans.
The EMC1422 has 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 EMC1422 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 temperature
exceeds a hardware specified threshold temperature. Additionally, the internal diodecan be configured
to assert the SYS_SHDN pin when the measured temperature exceeds user programmable limits.
Since the EMC1422 automatically corrects 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. Therefore, the EMC1422 can power up ready to operate for any system
configuration.
Figure 5.1
Conversion Rates
The EMC1422 may be configured for different conversion rates based on the system requirements.
The conversion rate is configured as described in
conversions per second. Other available conversion rates are shown in
Dynamic Averaging
Dynamic averaging causes the EMC1422 to measure the external diode channels for an extended time
based on the selected conversion rate. This functionality can be disabled for increased power savings
at the lower conversion rates (see
automatically adjust the sampling and measurement time for the external diode channels. This allows
shows a system level block diagram of the EMC1422.
Figure 5.1 System Diagram for EMC1422
DN1
EMC1422
DP1
Internal
Diode
DATASHEET
Section
SYS_SHDN
SMCLK
SMDATA
ALERT
15
6.4). When dynamic averaging is enabled, the device will
Section
Interface
Power Control
SMBus
Host
6.5. The default conversion rate is 4
Table
6.6.
Revision 1.16 (03-15-07)