1°C Triple Temperature Sensor with Resistance Error Correction
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.
EMC1023
DP1
Host
(SMSC SIO)
DN1
SMBus
SMBus
Interface
DP2
DN2
Internal
Diode
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 (∆VBE) of
a diode when operated at two different currents:
where:
k = Boltzmann’s constant
T = absolute temperature in Kelvin
q = electron charge
ηkT
q
IHIGH
ILOW
∆VBE =VBE _ HIGH −VBE _ LOW
=
ln
η = diode ideality factor
The change in ∆VBE voltage is proportional to absolute temperature T.
SMSC EMC1023
9
Revision 1.2 (04-15-05)
DATASHEET
SMSC [ SMSC CORPORATION ]
