1°C Triple Temperature Sensor with Resistance Error Correction

Datasheet

SMSC EMC1023

9

Revision 1.2 (02-05-07)

DATASHEET

Chapter 4 Product Description

The EMC1023 is an SMBus sensor that is capable of monitoring three temperature zones for use in

a personal computer or embedded environment. The part may be used as a companion to one of

SMSC’s broad line of SIO host circuits, or other devices capable of performing the SMBus host

function.

Figure 4.1 System Overview

In cooperation with the host device, thermal management can be performed as outlined in Figure 4.1

above. Thermal management consists of the host reading the temperature data from the remote and

internal temperature diodes of the EMC1023 and controlling the speed of one or multiple fans. Since

the EMC1023 incorporates one internal and two external temperature diodes, three separate thermal

zones can be monitored and controlled with this application. Also, measured temperature levels can

quickly be compared to preset limits within the host device which in turn will take the appropriate action

when values are found to be out of limit.

The EMC1023 has two basic modes of operation:

Run Mode: In this mode, the EMC1023 continuously converts temperature data and updates its

registers. The conversion rate is configured by the lower bits in the configuration register as

described in Section Table 4.8, "Configuration Register, Conversion Rate," on page 14.

Standby Mode: In this mode, the EMC1023 is powered down, drawing a maximum current of only

3uA. The SMBus is still operational and a one-shot command can be given which will force the

circuit to complete one full set of temperature conversions. The EMC1023 will return to Standby

Mode after the one shot conversion has finished.

4.1

Temperature Monitors

Thermal diode temperature measurements are based on the change in forward bias voltage (

a diode when operated at two different currents:

The change in

where:

k = Boltzmann’s constant

T = absolute temperature in Kelvin

q = electron charge

EMC1023

Host

(SMSC SIO)

SMBus

Interface

DP1

DN1

SMBus

Internal

Diode

DP2

DN2

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

=

−

=

Δ

LOW

HIGH

LOW

BE

HIGH

BE

BE

I

I

q

kT

V

V

V

ln

_

_

η