EMC1424 SMSC Corporation, EMC1424 Datasheet - Page 24

• Manufacturer Part Number: EMC1424
• Description: (EMC1423 / EMC1424) Temperature Sensor
• Manufacturer: SMSC Corporation

Revision 1.16 (03-15-07)
5.11
5.12
Substrate
PNP
Temperature Monitors
Temperature Measurement Results and Data
Δ
In general, thermal diode temperature measurements are based on the change in forward bias voltage
of a diode when operated at two different currents. This ΔV
as shown in the following equation:
Figure 5.7
the remote temperature diode, DN, is internally biased with a forward diode voltage referenced to
ground.
The temperature measurement results are stored in the internal and external temperature registers.
These are then compared with the values stored in the high and low limit registers. Both external and
internal temperature measurements are stored in 11-bit format with the eight (8) most significant bits
stored in a high byte register and the three (3) least significant bits stored in the three (3) MSB
positions of the low byte register. All other bits of the low byte register are set to zero.
The EMC1423 and EMC1424 have two selectable temperature ranges. The default range is from 0°C
to +127°C and the temperature is represented as binary number able to report a temperature from 0°C
to +127.875°C in 0.125°C steps.
The extended range is an extended temperature range from -64°C to +191°C. The data format is a
binary number offset by 64°C. The extended range is used to measure temperature diodes with a large
known offset (such as AMD processor diodes) where the diode temperature plus the offset would be
equivalent to a temperature higher than +127°C.
V
BE
I
LOW
Resistance
Correction
=
Error
shows a block diagram of the temperature measurement circuit. The negative terminal for
Figure 5.7 Block Diagram of Temperature Monitoring Circuit
η
kT
q
ln
⎛
⎜ ⎜
⎝
I
I
HIGH
LOW
I
HIGH
DN
DP
⎞
⎟ ⎟
⎠
DATASHEET
Aliasing
Filter
24
Anti-
1°C Temperature Sensor with Hardware Thermal Shutdown
where:
k = Boltzmann’s constant
T = absolute temperature in Kelvin
q = electron charge
η
= diode ideality factor
BE
is proportional to absolute temperature
ADC
SMSC EMC1423/EMC1424
ΔΣ
Datasheet
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