W83697HF/F
5 0 K W
Vin = V C C ´
@ 2 .9 8 V
5 0 K W + 3 4 K W
where VCC is set to 5V.
The Pin 61 is connected to 5VSB voltage. W83697HF monitors this voltage and the internal two serial
W
W
resistors are 17K and 33K so that input voltage to ADC is 3.3V which less than 4.096V of ADC
maximum input voltage.
9.3.2 Monitor negative voltage:
The negative voltage should be connected two series resistors and a positive voltage VREF (is equal to
3.6V). In the Figure 9.2, the voltage V2 and V3 are two negative voltage which they are -12V and -5V
respectively. The voltage V2 is connected to two serial resistors then is connected to another terminal
VREF which is positive voltage. So as that the voltage node N12VIN can be obtain a posedge voltage if
the scales of the two serial resirtors are carefully selected. It is recommanded from Winbond that the
scale of two serial resistors are R3=232K ohms and R4=56K ohm. The input voltage of node N12VIN can
be calculated by following equation.
232KW
N12VIN (VREF V ) (
) V
+
2
=
+
´
2
232KW + 56KW
where VREF is equal 3.6V.
If the V2 is equal to -12V then the voltage is equal to 0.567V and the converted hexdecimal data is set
to 35h by the 8-bit ADC with 16mV-LSB.This monitored value should be converted to the real negative
votage and the express equation is shown as follows.
N12VIN - VREF ´ b
V2 =
1 - b
b
Where is 232K/(232K+56K). If the N2VIN is 0.567 then the V2 is approximately equal to -12V.
The another negative voltage input V3 (approximate -5V) also can be evaluated by the similar method
and the serial resistors can be selected with R5=120K ohms and R6=56K ohms by the Winbond
recommended. The expression equation of V3 With -5V voltage is shown as follows.
N5VIN - VREF ´ g
V3 =
1 - g
g
Where the is set to 120K/(120K+56K). If the monitored ADC value in the N5VIN channel is 0.8635,
g
VREF=3.6V and the parameter is 0.6818 then the negative voltage of V3 can be evalated to be -5V.
Publication Release Date: Feb. 2002
- 86 -
Revision 0.70
WINBOND [ WINBOND ]
