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S1F76540 Series
S1F70000 Series EPSON 2–27
Technical Manual
S1F76540
Series
Changing the temperature coefficient:
• The temperature coefficient of the regulated voltage depends on the temperature coefficient of the reference
voltage (if the division ratio of setup resistors does not depend on the temperature). It is necessary to change the
temperature coefficient using thermistors, resistors or others to set any other temperature coefficient of the
regulated voltage. The following explains how to calculate the V
REG voltage in temperature T.
V
REG (T) = 1 +
C
TR2 × R2 (T0)
× 1+ (T – T
0
) ×
C
T
• • • • Equation (3)
C
TR1 × R1 (T0) 100
T
0 :25°C
C
TR1 : Temperature coefficient of resistor R1 (Ratio to the value at 25°C)
C
TR2 : Temperature coefficient of resistor R2 (Ratio to the value at 25°C)
C
T : Temperature coefficient of internal reference voltage (%/°C)
R1 (T
0) : R1 value (Ω) at 25°C
R2 (T
0) : R2 value (Ω) at 25°C
V
REF (T0) : Internal reference voltage (V) at 25°C
If the temperature coefficient of R1 and R2 is identical in equation (3), the V
REG voltage depends on the tem-
perature coefficient of internal reference voltage only.
Application notes on voltage regulator circuit:
• To satisfy the absolute maximum ratings of the S1F76540, the setup resistor(s) must be inserted between V
DD
and VREG pins of the S1F76540 that uses the voltage regulator. The S1F76540 IC itself may be degraded or
destroyed if the R1 resistor is connected to pin V
DD of S1F76540 that does not use the regulator during serial
connection.
• The regulation voltage adjustment input (pin RV) has the very high input impedance, and its noise insertion can
drop the regulator stability. As shown in Figure 2.5, shield the cable between the division resistor and RV pin or
use a cable as short as possible between them.
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