EMC1402 Datasheet, PDF (16/37 Pages) SMSC Corporation – 1°C Temperature Sensor with Beta Compensation

Chapter 5 Product Description
1°C Temperature Sensor with Beta Compensation
Datasheet
The EMC1402 is an SMBus temperature sensor. The EMC1402 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 EMC1402 and using
that data to control the speed of one or more fans.
The EMC1402 has 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 EMC1402 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 EMC1402 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 EMC1402 can power up ready to operate for any system
configuration.
Figure 5.1 shows a system level block diagram of the EMC1402.
CPU
Thermal
diode
EMC1402
DP1
DN1
Internal
Diode
Host
SMCLK
SMDATA
ALERT
SMBus
Interface
THERM
Power Control
5.1
Figure 5.1 System Diagram for EMC1402
Modes of Operation
The EMC1402 has two modes of operation.
„ Active (Run) - In this mode of operation, the ADC is converting on all temperature channels at the
programmed conversion rate. The temperature data is updated at the end of every conversion and
the limits are checked. In Active mode, writing to the one-shot register will do nothing.
„ Standby (Stop) - In this mode of operation, the majority of circuitry is powered down to reduce
supply current. The temperature data is not updated and the limits are not checked. In this mode
of operation, the SMBus is fully active and the part will return requested data. Writing to the one-
shot register will enable the device to update all temperature channels. Once all the channels are
updated, the device will return to the Standby mode.
Revision 1.16 (03-15-07)
16
DATASHEET
SMSC EMC1402