f75367 Feature Integration Technology Inc., f75367 Datasheet - Page 9

• Manufacturer Part Number: f75367
• Description: Temperature Sensor With I2c-sst Bridge
• Manufacturer: Feature Integration Technology Inc.

6.3 Beta Compensation
The F75367 is configured to detect the temperature of diodes (e.g. 2N3906) or CPU thermal diodes. The
diode can be connected in different way as below Figure.
The basic of the temperature sensor follows mathematical formula as below:
The F75367 measures temperature from the thermal diodes by the basic. In traditional case, the F75367
outputs dual currents to a thermal diode. Then the F75367 calculates the absolute temperature by △VBE.
For discrete transistor (i.e. 2N3906), the beta is normally very high such that the percent change in beta
is very small. For example, 15% variation in beta for two forced IE currents and the beta is 50 would
contribute about 0.32℃ error per 100℃. For Substrate PNP transistor (i.e. CPU), the beta is very small
such that the proportional beta variation will very high, and it will cause large error in temperature
Remote-sensor transistor manufacturers
Manufacturer
Panasonic
Philips
100°C
140°C
50°C
75°C
90°C
∆
V
Substrate PNP transistor
i.e. CPU
BE
=
Model Number
2SB0709 2N3906
PMBT3906
KT
q
0101 1010
0011 0010
0100 1011
0110 0100
1000 1100
×
ln
Ie
Ie
1
2
=
D+
D-
KT
q
9
×
ln
 +
 

 +
 

0.375°C
0.500°C
0.625°C
0.750°C
0.875°C
1
1
β
β
Discrete PNP transistor
i.e. 2N3906
2
β
1
β
2
1

 


 

Ic
Ic
1
2
100 0 0000
101 0 0000
011 0 0000
110 0 0000
111 0 0000
D+
D-
F75367
Feb..
V0.11P
, 2008