F75334DG Datasheet, PDF (17/66 Pages) Feature Integration Technology Inc. – Performance Controller

11111111_111xxxx1Æ - 0.125
11011011_111xxxx1Æ - 25.125
11010000_111xxxx1Æ -48.125 (-25.125 - 23) (offset)
Remote-sensor transistor manufacturers
Manufacturer
Model Number
Panasonic
2SB0709 2N3906
Philips
PMBT3906
F75334
Monitor Temperature from “thermistor”
The F75334DG can connect three thermistor to measure environment temperature or
remote temperature. The specification of thermistor should be considered to (1) β value is
3435K (2) resistor value is 10K ohm at 25°C. In the Figure 7-1, the thermistor is connected by
a serial resistor with 10K ohm, then connected to VREF.
Monitor Temperature from “thermal diode”
Also, if the CPU, GPU or external circuits provide thermal diode for temperature
measurement, the F75334DG is capable to these situations. The build-in reference table is for
PNP 2N3906 transistor, and each different kind of thermal diode should be matched with
specific BJT gain. In the Figure 7-1, the transistor is directly connected into temperature pins.
ADC Noise Filtering
The ADC is integrating type with inherently good noise rejection. Micro-power operation
places constraints on high-frequency noise rejection; therefore, careful PCB board layout and
suitable external filtering are required for high-accuracy remote measurement in electronically
noisy environment. High frequency EMI is best filtered at D+ and D- with an external 2200pF
capacitor. Too high capacitance may introduce errors due to the rise time of the switched
current source. Nearly all noise sources tested cause the ADC measurement to be higher
than the actual temperature, depending on the frequency and amplitude.
10
July, 2007
V0.25P