S-812C_1 Datasheet, PDF (19/52 Pages) Seiko Instruments Inc – HIGH OPERATING VOLTAGE CMOS VOLTAGE REGULATOR

Rev.4.0_00
HIGH OPERATING VOLTAGE CMOS VOLTAGE REGULATOR
S-812C Series
2. Constant Current Circuit
This circuit can be used as a constant current circuit if making the composition seen in Figure 19 and
20. Constant current I_O is calculated from the following equation:
I_O = (V_OUT(E) ÷ R_L) + I_SS
(V_OUT(E) = effective output voltage)
Note that by using a circuit in Figure 19, it is impossible to set the better driving ability to the constant
amperage (I_O) than the S-812C Series basically has.
To gain the driving ability which exceeds the S-812C Series, there’s a way to combine a constant
current circuit and a current boosting circuit, as seen in Figure 20.
The maximum input voltage for a constant current circuit is 16 V + the voltage for device (V_O).
It is not recommended to add a capacitor between the VIN (power supply) and VSS pin or the VOUT
(output) and VSS pin because the rush current flows at power-on.
VIN
GND
VIN S-812C VOUT
Series
VSS ON/OFF ^{RL VOUT}
C_IN
I_O
V_O
Device
Figure 19 Constant Current Circuit
Tr1
V_IN
GND
S-812C
Series
R₁
ON/OFF VSS
C_L
VOUT
R_L ^VOUT
I_O
V_O
Device
Figure 20 Constant Current Boost Circuit
3. Output Voltage Adjustment Circuit
(Only for S-812CxxA Series (No short-circuit protection, power-off function))
By using the composition seen in Figure 21, users are able to increase the output voltage. The value of
output voltage V_OUT1 is calculated from the following equation:
V_OUT1 = V_OUT(E) × (R₁ + R₂) ÷ R₁ + R₂ × I_SS
(V_OUT(E) = effective output voltage)
Set the value of resistors R1 and R2 so that the S-812C Series is not affected by current consumption
I_SS.
Capacitor C₁ reduces output fluctuation due to power-on, power fluctuation and load fluctuation. Set the
value according to the actual evaluation.
It is not recommended to add a capacitor between the VIN (power supply) and VSS pin or the VOUT
(output) and VSS pin because it causes output fluctuation and output oscillation due to power-on.
VIN V_IN S-812C
Series
GND
VSS
C_IN
C₁
VOUT
R₁
R₂
V_OUT1
C_L
Figure 21
Seiko Instruments Inc.
19