1°C Triple SMBus Sensor with Resistance Error Correction

Datasheet

SMSC EMC1033

9

Revision 1.1 (01-19-07)

DATASHEET

Chapter 4 Product Description

The EMC1033 is an SMBus sensor that can monitor internal temperature and one or two remote diode

temperatures. The sensor is typically used with an SMBus host such as an SMSC SIO device or an

SMSC fan control chip.

Thermal management is performed in cooperation with the host device. The host reads the

temperature data from the EMC1033 and takes appropriate action such as controlling fan speed or

processor clock frequency. The EMC1033 has programmable temperature limit registers that define a

safe operating window. After the host has configured the temperature limits, the EMC1033 can perform

as a free-running independent watchdog to warn the host of temperature hot spots without requiring

the host to poll the device.

Figure 4.1 System Overview

Two separate temperature zones are monitored using only two pins on the EMC1033. This is

accomplished using two anti-parallel diodes as shown in Figure 4.1. This technique maintains high

accuracy while minimizing pin count and reducing board routing complexity. The anti-parallel diode

architecture performs very well with diode connected transistors. It is not compatible with substrate

transistors (sometimes called thermal diodes or on-chip sense junctions). See the complete list of

temperature sensor products available from SMSC for devices that can measure two or more remote

zones including substrate transistors. The connections for the two discrete transistors are shown in

Figure 4.2

Figure 4.2 Anti-parallel Diodes

The EMC1033 has

Run Mode: In this mode, the EMC1033 continuously converts temperature data and updates its

registers. The rate of temperature conversion is configured as shown in Section 4.12, "Conversion

Rate Register," on page 17.

Standby Mode: In this mode, the EMC1033 is placed in standby to conserve power as described

in Section 4.7, "Standby Mode," on page 13.

ADDR/THERM

ALERT/THERM2

Host

Fan

Driver

SMDATA

SMCLK

SMBus

Interface

EMC1033

DP1/DN2

DN1/DP2

Internal

Diode

Typical remote

discrete PNP transistor

i.e. 2N3906

Typical remote

discrete NPN transistor

i.e. 2N3904

to DP1/DN2

to DN1/DP2

to DP1/DN2

to DN1/DP2