1°C Triple Temperature Sensor with Resistance Error Correction & Hotter of Two Zones

Datasheet

SMSC EMC1053

15

Revision 1.44 (04-14-08)

DATASHEET

When monitoring the thermal diode of an AMD K8 processor, the Resistance Error Correction must be

disabled for accurate temperature measurements. This is accomplished by clearing the REC bit in the

configuration 2 register (see Section 4.5). Please see Application note “13.16 - Using the EMC1043

with AMD Processors” for more details.

3.7

Beta Compensation

The Beta Compensation function can be programmed to eliminate temperature errors caused by beta

variation in modern, low beta transistors used for monitoring processor temperatures.

Changes in

beta as differing currents are applied to temperature transistors can cause significant temperature

errors in monitoring devices. As modern processor geometries shrink the trend is for transistor betas

to decrease, which exacerbates temperature errors.

By default, this functionality is disabled. It can be enabled by writing any value other than 07h in the

Beta Configuration Registers (see Section 4.11).

Discrete transistors, with collector connected to base to form a diode, are generally immune to these

temperature errors because of high (>100) betas. A beta variation of 10% from low current to high

current, when beta equals 100, induces approximately 0.12° error at 100°C. However for a low beta

(1.0) substrate transistor used for processor temperature measurement, a beta variation of 10% from

low to high current induces approximately 6.12° error at 100°C.

When measuring an AMD K8 processor, the Beta Compensation circuitry must be disabled. See

Section 4.8. Please see SMSC Application note “13.16 - Using the EMC1043 with AMD Processors”

for more details.

3.8

Programmable Ideality Factor

The EMC1053 default is for a diode ideality factor of 1.008 which is common for a 2N3904 diode and

for many processor transistors. When a diode or transistor is used that has a different ideality factor

value than 1.008 a temperature error is induced that is a linear function of temperature. Previous

solutions for this mismatch in ideality factor has been to supply a programmable offset to the

temperature reading which corrects the error at a single temperature but causes a residual error at all

other temperatures. The EMC1053 ideality factor register corrects this mismatch error at all

temperatures (see Section 4.7).

APPLICATION NOTE: When monitoring a substrate transistor or CPU diode and beta compensation is enabled, the

Ideality Factor should not be adjusted. Beta Compensation automatically corrects for most

ideality errors.

3.9

Diode Faults

The EMC1053 detects a fault if the DP pin is left floating or is shorted to VDD. In the case of a diode

fault, the corresponding status bit will be set and the output data will be set at 400h.