emc2105 Standard Microsystems Corp., emc2105 Datasheet - Page 76

• Manufacturer Part Number: emc2105
• Description: Emc2105 Rpm-based High Side Fan Controller With Hardware Thermal Shutdown
• Manufacturer: Standard Microsystems Corp.

Appendix A Thermistors
Revision 1.74 (05-08-08)
The EMC2105 can monitor thermistor inputs on the TRIP_SET / VIN4 as well as supporting a
thermistor option on the all of the external diode pins pairs (DP1 / VREF_T1 and DN1 / VIN1,etc.).
The Thermistors can be connected as shown in
Figure A.1
DN1 / VIN1, DP2 / VREF_T2 and DN2 / VIN2.
The top side resistor is internally integrated in the case of the TRIP_SET / VIN4 channel and the VREF
voltage will not be brought out externally. The Thermistor should be connected in the same way as
RSET.
The relationship between voltage and temperature is roughly linear. the measured voltage by the
EMC2105 will be inversely proportional to temperature .
Linearization methods can only accurately capture the temperature over a limited window of
temperatures.
For a 10k Ohm type 3370 Thermistor and a 1.2k ohm ±1% setting resistor, the output response
corresponding to a thermistor is tabulated in
If the INV_VINx bit is set then the results of the circuit (configured as shown in
in
The EMC2105 does not perform any numerical calculations on the thermistor value if a thermistor is
monitored on TRIP_SET / VIN4 pin. If the External Diode 1, External Diode 2, or External Diode 3
channels are configured to measure a thermistor, it must be configured as shown in
When measuring a thermistor input with Fan Control Look Up Table, care must be taken that the
temperature thresholds are entered as a unsigned voltage number that corresponds to the desired
thermal threshold. Also note that the LUT assumes that the VIN1 and TRIP_SET / VIN4 voltage inputs
are directly proportional to temperature.
Thermistor
10K 1%
Table
1.2K
1%
A.2.
is representative of one of the thermistor channels and will apply to DP1 / VREF_T1 and
Figure A.1 “Low Side” Thermistor Connection
0.1uF
DP3 / DN4 / VREF_T3
DATASHEET
RPM-Based High Side Fan Controller with Hardware Thermal Shutdown
DN3 / DP4 / VIN3
76
Table
Figure
A.1.
A.1.
EMC2104/5/6
Buffer
ADC
Reference
Voltage
Figure
Figure
SMSC EMC2105
A.1) is shown
A.1.
Datasheet