1.5°C SMBus Temperature Sensor in Miniature SOT-23
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
device. The
ADDR
/
THERM
output can be used to control a fan without host intervention.
EMC1001
SMCLK
SMDATA
Internal
Diode
ALERT/THERM2
Host
SMBus
Interface
ADDR/THERM
Fan
Driver
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
Standby Mode: In this mode, the EMC1001 is placed in standby to conserve power as described
in
4.1
Temperature Monitors
Thermal diode temperature measurements are based on the change in forward bias voltage (ΔV
BE
) of
a diode when operated at two different currents:
where:
Δ
V
BE
=
V
BE
_
HIGH
−
V
BE
_
LOW
⎛
I
ln
⎜
HIGH
=
⎜
I
q
⎝
LOW
η
kT
⎞
⎟
⎟
⎠
k
= Boltzmann’s constant
T
= absolute temperature in Kelvin
q
= electron charge
η
= diode ideality factor
The change in
Δ
V
BE
voltage is proportional to absolute temperature T.
SMSC EMC1001
9
Revision 1.6 (01-29-07)
DATASHEET
SMSC [ SMSC CORPORATION ]
