EMC1043-4-ACZL SMSC, EMC1043-4-ACZL Datasheet - Page 16

• Manufacturer Part Number: EMC1043-4-ACZL
• Description: Board Mount Temperature Sensors Temp Snsr
• Manufacturer: SMSC

Specifications of EMC1043-4-ACZL

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

APPLICATION NOTE: When monitoring a substrate transistor or CPU diode and beta compensation is enabled, the
Revision 1.44 (04-14-08)
3.8
3.9
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.
Because the Beta Compensation function is designed to be used with substrate PNP transistors only,
this function should be disabled when using a diode-connected transistor (such as the 2N3904) or
CPUs that implement the thermal diode as a two-terminal device. The Beta Compensation function is
disabled by writing 07h to the Beta Configuration register
When measuring an AMD K8 processor, the Beta Compensation circuitry must be disabled. See
Section
for more details.
The EMC1043 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 EMC1043 ideality factor register corrects this mismatch error at all
temperatures (see
The EMC1043 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.
Programmable Ideality Factor
Diode Faults
4.8. Please see SMSC Application note “13.16 - Using the EMC1043 with AMD Processors”
Ideality Factor should not be adjusted. Beta Compensation automatically corrects for most
ideality errors.
Section
4.7).
1°C Triple Temperature Sensor with Beta Compensation and Hotter of Two Zones
DATASHEET
16
SMSC EMC1043
Datasheet