EMC1438 Datasheet, PDF (17/48 Pages) SMSC Corporation – 1°C Multiple Temperature Sensor with Hardware Controlled Standby & Hottest of Multiple Zones

1°C Multiple Temperature Sensor with Hardware Controlled Standby & Hottest of Multiple Zones
Datasheet
Chapter 5 Product Description
The EMC1438 is an SMBus temperature sensor that monitors up to seven (7) external diodes and one
internal 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 EMC1438 and using
that data to control the speed of one or more fans.
The EMC1438 provides two levels of monitoring. The first EMC1438 provides a maskable ALERT
signal to the host when measured temperatures meet or exceed user programmable limits. This allows
the EMC1438 to be used as an independent thermal watchdog to warn the host of temperature hot
spots without constant monitoring by the host. The second level of monitoring provides a non-maskable
interrupt on the THERM pin if the measured values meet or exceed a second programmable limit.
Because the EMC1438 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 devices without resistance error correction. As well,
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 device can power up ready to operate for any system
configuration including those diodes that require the BJT or transistor model.
Figure 5.1 shows a system level block diagram of the EMC1438.
CPU
Optional
anti-
parallel
diodes
Optional
anti-
parallel
diodes
Optional
anti-
parallel
diodes
VDD
EMC1438
DP1
THERM
DN1
SMDATA
SMCLK
DP2 / DN3
ALERT
DN2 / DP3
DP4 / DN5
DN4 / DP5
DP6 / DN7
STANDBY
ADDR_SEL
DN6 / DP7
Host
SMBus
Interface
Figure 5.1 System Diagram for EMC1438
5.1 Register Bits
Unless otherwise stated when a bit is “set”, it is written to a logic ‘1’. Likewise when a bit is “cleared”,
it is written to a logic ‘0’.
SMSC EMC1438
17
DATASHEET
Revision 1.0 (04-29-10)