
W83627HF/F
PRELIMINARY
Publication Release Date: Jul 1999
Revision 0.53
- 95 -
V
VCC
K
+
K
K
V
in
=
×
50
50
34
2 98
.
where VCC is set to 5V.
The Pin 61 is connected to 5VSB voltage. W83627HF monitors this voltage and the internal two serial
resistors are 17K
and 33K
so that input voltage to ADC is 3.3V which less than 4.096V of ADC
maximum input voltage.
11.3.2 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 11.2, 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.
N
VIN
VREF
(
V
K
+
K
K
V
12
232
232
56
2
2
=
+
×
+
)
(
)
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.
N
VIN
2
1
V
VREF
12
=
×
Where
β
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.
N VIN
3
1
V
VREF
5
=
×
Where the
γ
is set to 120K/(120K+56K). If the monitored ADC value in the N5VIN channel is 0.8635,
VREF=3.6V and the parameter
γ
is 0.6818 then the negative voltage of V3 can be evalated to be -5V.