EMC1203 Standard Microsystems Corporation, EMC1203 Datasheet - Page 6

• Manufacturer Part Number: EMC1203
• Description: Triple/quad Single-wire Temp Sensor in Msop-8 Using SMSC Budgetbus Sensor Interface
• Manufacturer: Standard Microsystems Corporation

Chapter 3 Product Description
Revision 1.1 (06-12-06)
3.1
The EMC1203 and EMC1204 are 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.
"System Overview"
In cooperation with the host device, thermal management can be performed as shown in
Thermal management consists of the host acquiring the temperature data from the EMC1203 and
EMC1204 controlling the speed of one or more fans. 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 EMC1203 and the DP1/DN1 port of the EMC1204 are compatible with CPU substrate diodes.
Two separate temperature zones are monitored using only two pins on the EMC1204. This is
accomplished using two anti-parallel diodes as shown on the pins DP2/DN3 and DN2/DP3 in
Figure
routing complexity. The anti-parallel diode architecture performs very well with diode connected
transistors. It is not compatible with substrate transistors (sometimes called thermal diodes or on-chip
sense junctions).
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
Temperature Monitors
Δ
3.1. This technique maintains high accuracy while minimizing pin count and reducing board
V
BE
=
V
Δ
BE
V
_
BE
DP1
DN1
HIGH
DP2/DN3
DN2/DP3
shows a typical system overview:
voltage is proportional to absolute temperature T.
EMC1203/
EMC1204
−
V
BE
Figure 3.1 System Overview
Triple/Quad Single-Wire Temp Sensor in MSOP-8 Using SMSC BudgetBus
BBUS
_
LOW
DATASHEET
=
η
kT
q
4
ln
⎛
⎜ ⎜
⎝
I
I
Interface
HIGH
LOW
BBUS
(KBC1100)
⎞
⎟ ⎟
⎠
Host
where:
k = Boltzmann’s constant
T = absolute temperature in Kelvin
q = electron charge
η
= diode ideality factor
SMSC EMC1203/EMC1204
TM
Sensor Interface
Figure 3.1,
Figure
Datasheet
BE
3.1.
) of