F71862
resistors so as to obtain the input range. Only 3VCC/VSB/VBAT is an exception for it is main
power of the F71862. Therefore 3VCC/VSB/VBAT can directly connect to this chip’s power
pin and need no external resistors. There are two functions in this pin with 3.3V. The first
function is to supply internal analog power of the F71862 and the second function is that
voltage with 3.3V is connected to internal serial resistors to monitor the +3.3V voltage. The
internal serial resistors are two 150K ohm, so that the internal reduced voltage is half of
+3.3V.
There are four voltage inputs in the F71862 and the voltage divided formula is shown as
follows:
R2
VIN = V+12V
×
R1 + R2
where V+12V is the analog input voltage, for example.
If we choose R1=27K, R2=5.1K, the exact input voltage for V+12v will be 1.907V,
which is within the tolerance. As for application circuit, it can be refer to the figure shown as
follows.
150K
150K
3VCC/VSB
(directly connect to the chip)
VIN3.3
VIN (Lower than 2.048V)
(directly connect to the chip)
VIN1(Max2.048V)
Voltage Inputs
VIN(Higher than 2.048V)
R1
R2
8-bit ADC
with
VREF
8 mV LSB
R
10K, 1%
D+
D-
Typical Thermister
Connection
Typical BJT
Connection
2N3906
R
THM
10K, 25 C
Fig 7-1
The F71862 monitors three remote temperature sensors.These sensors can be measured
from -40°C to 127°C. More detail please refer register description.
Remote-sensor transistor manufacturers
Manufacturer
Panasonic
Philips
Model Number
2SB0709 2N3906
PMBT3906
42
July, 2008
V.28P
FINTEK [ FEATURE INTEGRATION TECHNOLOGY INC. ]
