emc1201 Standard Microsystems Corp., emc1201 Datasheet - Page 6

• Manufacturer Part Number: emc1201
• Description: Single/dual Single-wire Temp Sensor In Sot23-5
• Manufacturer: Standard Microsystems Corp.

Chapter 3 Product Description
Revision 1.0 (06-10-08)
3.1
Temperature Monitors
The EMC1201 and EMC1202 are SOT23 temperature sensors with a proprietary single wire SMSC
BudgetBus™ Sensor Interface. Temperature information is communicated to a host device via the
serial bus. All intelligence regarding the interpretation of temperature resides in the host.
shows a typical system overview:
Thermal management consists of the host acquiring the temperature data from the EMC1201 or
EMC1202 and controlling the speed of one or more fans. Because the EMC1202 incorporates one
internal and one external temperature diode, up to two separate thermal zones can be monitored and
controlled. The host has the ability to compare measured temperature levels to preset limits and take
the appropriate action when values are found to be out of limit. The EMC1202 is compatible with CPU
substrate diodes.
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
Δ
V
BE
=
V
Δ
BE
V
_
BE
DP
DN
EMC1202
HIGH
voltage is proportional to absolute temperature T.
BBUS
−
V
BE
Figure 3.1 System Overview
Single/Dual Single-Wire Temp Sensor in SOT23-5 Using SMSC BudgetBus
_
LOW
DATASHEET
=
η
kT
q
6
Interface
BBUS
ln
(KBC1100)
⎛
⎜ ⎜
⎝
I
I
Host
HIGH
LOW
⎞
⎟ ⎟
⎠
where:
k = Boltzmann’s constant
T = absolute temperature in Kelvin
q = electron charge
η
= diode ideality factor
SMSC EMC1201/EMC1202
TM
Sensor Interface
Figure 3.1
Datasheet
BE
) of