5. FUNCTIONAL DESCRIPTION
S1F76540M0C Series Technical Manual
EPSON
7
(Rev.1.1)
5.4 Voltage Stabilizer
The voltage stabilizer stabilizes the voltage input to the VRI pin and outputs any voltage. The output voltage
can be changed to any value based on the ratio between external split resistances R1 and R2 as shown in the
expression (see Section 5.1). In this case, the sum of these split resistances should be as small as possible to
limit influence of external noises; however, the current consumed for the split resistances will increase as shown
in the expression (see Section 5.2). Therefore, the sum of split resistance values should be approximately 100
Ω
to 1M
Ω
.
The temperature coefficient of the stabilizing potential will become equal to that of the reference voltage
described in Section 5.3.
Figure 5.3 V
REG
setting method and assembly consideration
[Setting method]
y
Relational expression between V
REG
and reference voltage
y
Consumption current for split resistances
[Setting example]
The following shows a setting example for outputting V
REG
= -18V when VI = -5V and VO = -20V at
quadruple boosting.
Determine the total resistor value of split resistances R1 and R2. If the allowable consumption current of the
split resistances is 20
µ
A, the following will be obtained from expression (5.2).
R1+R2 = 18V
÷
20
µ
A = 900k
Ω
If the reference voltage is -1.5V, the following ratio of the split resistances will be obtained from expression
(5.1).
(R1+R2)
÷
R1 = (-18V)
÷
(-1.5V) = 12
I
REG
=
･････
Expression (5.2)
|
V
REG
|
R1+R2
×
(Reference voltage)
･････
Expression (5.1)
V
REG
=
R1
+
R2
R1
VO
1
R2
VRI
V
REG
RV
V
DD
FC
TC1
TC2
C2P
C2N
C3N
C1N
C1P
VI
POFF1X
POFF2X
2
3
4
5
6
7
8
1
9
1
1
1
1
1
1
R1
1
