F71869A
127°C
Open
1111 1111
1000 0000
5.2.2. Monitor Temperature from “Thermistor”
The F71869A can connect three thermistors to measure environment temperature or
remote temperature. The specification of thermistor should be considered to (1) ß value is
3435K (2) resistor value is 10K ohm at 25ºC. In the Figure 2, the thermistor is connected by
a serial resistor with 10K ohm, then being connected to VREF.
5.2.3. Monitor Temperature from “Thermal diode”
Also, if the CPU, GPU or external circuits provide thermal diode for temperature
measurement, the F71869A is capable to these situations. The build-in reference table is for
PNP 2N3906 transistor. In the Figure 2, the transistor is directly connected into temperature
pins.
5.2.4. 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.
5.2.5. Monitor Temperature from “SMBus device”
F71869A provides SMBus block read/write compatible Platform Control Hub (PCH) EC
SMBus protocol, and provides byte read/write protocol to read CPU and chipset thermal
temperature information. For byte read /write protocol, F71869A supports 4-suit device
address to read or write from device information. For block read/write, F71869A support 1
suits device address and maximum 17 byte count for read protocol to read from device
information, and 4 byte count for write protocol to write information to device.
5.2.6. Monitor Temperature from “PECI”
F71869A support Intel PECI1.1/PECI3.0/PECI_Request/PECI_Available interfaces to
read temperature from PECI device.
24
Oct., 2011
V0.19P
FINTEK [ FEATURE INTEGRATION TECHNOLOGY INC. ]
