1.5°C SMBus Temperature Sensor in Miniature SOT-23

Datasheet

SMSC EMC1001

9

Revision 1.6 (01-29-07)

DATASHEET

Chapter 4 Product Description

The EMC1001 is an SMBus temperature that monitors a single temperature zone. Thermal

management is performed in cooperation with a host device. The host reads the temperature data from

the EMC1001 and takes appropriate action such as controlling fan speed or processor clock frequency.

The EMC1001 has programmable temperature limit registers that define a safe operating window. After

the host has configured the temperature limits, the EMC1001 can operate as a free-running

independent watchdog to warn the host of temperature hot spots without requiring the host to poll the

Figure 4.1 Controlling a fan without host intervention.

The EMC1001 has two basic modes of operation:

Run Mode: In this mode, the EMC1001 continuously converts temperature data and updates its

registers. The rate of temperature conversion is configured as shown in Section 4.9 on page 14.

Standby Mode: In this mode, the EMC1001 is placed in standby to conserve power as described

in Section 4.5 on page 12.

4.1

Temperature Monitors

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

ΔV

a diode when operated at two different currents:

The change in

where:

k = Boltzmann’s constant

T = absolute temperature in Kelvin

q = electron charge

ADDR/THERM

ALERT/THERM2

EMC1001

Host

Fan

Driver

SMDATA

Internal

Diode

SMCLK

SMBus

Interface

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

=

−

=

Δ

LOW

HIGH

LOW

BE

HIGH

BE

BE

I

I

q

kT

V

V

V

ln

_

_

η