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5. FUNCTIONAL DESCRIPTION
Therefore R1 and R2 will be determined as follows.
R1 = 75kΩ
R2 = 825kΩ
[Changing the temperature coefficient]
The temperature coefficient of the stabilizing potential depends on that of the reference voltage described in
Section 5.3. (Case where the split ratio of resistance values for setting does not depend on the temperature)
When setting the temperature coefficient other than that specifiable in S1F76540 to the stabilizing potential,
change it using a thermistor resistor, etc. shown in Figure 9.15.
The following shows how to obtain the V
CTR2×R2(T0)
V
(T) = {1+
REG
CTR1×R1(T0)
T0
:
25°C
CTR1
:
Temperature coefficient of resistance R1 (Ratio between split resistance values at 25°C)
CTR2
:
Temperature coefficient of resistance R2 (Ratio between split resistance values at 25°C)
CT
:
Temperature coefficient (%/°C) of internal reference voltage
R1(T0)
:
25°R1 value (Ω) at 25°C
R2(T0)
:
25°R2 value (Ω) at 25°C
V
(T0)
:
25°Internal reference voltage value (V) at 25°C
REF
If the temperature coefficient of R1 is equal to that of R2 in expression (5.3), V
temperature coefficient of the internal reference voltage.
[Notes on using the voltage stabilization circuit]
• To keep the S1F76540 absolute maximum rating, the setting resistor must be connected between V
V
of an S1F76540 that uses the regulator. Connecting R1 to V
REG
regulator when connecting the S1F76540 in series will result in deterioration or destruction in this IC.
• The stabilizing potential adjusting pin "RV" has the too high input impedance, which may result in the
regulator being destabilized due to noises. When using this pin, shield the wiring section between the split
resistor and RV pin, or shorten the wiring as much as possible (see Figure 5.3).
• When using the stabilizing power supply voltage pin "VRI", short-circuit the VRI and VO pins with a shorter
cable (see Figure 5.3), exceeding at high-magnification boosting using an external diode shown in Section 9.8.
[Measures against oscillation]
Installing external parts enables you to take measures of oscillation.
The following shows the parts used and recommended values.
• Capacity between V
REG
• Serial equivalent resistance of output capacitor CO
(Note 1) Specify the minimum necessary value because the ripple value of the output voltage increases.
(See item 9.4.)
8
value at temperature T.
REG
×{1+(T－T0) ×
and RV
:
220pF
EPSON
CT
} × V
(T0)
･････Expression (5.3)
REF
100
of an S1F76540 that does not use the
DD
:
10Ω or more (Note 1)
S1F76540M0C Series Technical Manual
depends only on the
REG
and
DD
(Rev.1.1)
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