S-812C_1 Datasheet, PDF (18/52 Pages) Seiko Instruments Inc – HIGH OPERATING VOLTAGE CMOS VOLTAGE REGULATOR

HIGH OPERATING VOLTAGE CMOS VOLTAGE REGULATOR
S-812C Series
Rev.4.0_00
„ Selection of External Components
1. Output Capacitor (C_L)
The S-812C Series has an internal phase compensation circuit which stabilizes the operation regardless
of the change of output load. Therefore it is possible for users to have a stable operation without an
output capacitor (C_L). However, the values of output overshoot and undershoot, which are the
characteristics of transient response, vary depending on the output capacitor. In selecting the value of
output capacitor, refer to the data on C_L dependency in “„ Reference data 1. Transient response
characteristics”.
Set ESR 10 Ω or less when using a tantalum capacitor or an aluminum electrolytic capacitor. Pay
attention at low temperature, that aluminum electrolytic capacitor especially may oscillate because ESR
increases. Evaluate sufficiently including the temperature characteristics in use.
„ Application Circuit
1. Output Current Boost Circuit
As shown in Figure 18, the output current can be boosted by externally attaching a PNP transistor.
Between the input voltage V_IN and the VIN pin (for power supply) in the S-812C Series, if setting the
base-emitter voltage VBE which fully switches the PNP transistor on, S-812C Series controls the base
current in a PNP transistor so that the output voltage V_OUT reaches the level of voltage which is set by
the S-812C Series.
Since the output current boosting circuit in Figure 18 does not have the good characteristics of transient
response, under the usage condition, confirm if output fluctuation due to power-on, and fluctuations of
power supply and load affect on the operation or not before use.
Note that the short-circuit protection circuit in the S-812C Series does not work as short-circuit protection
for this boost circuit.
Tr1
VIN S-812C
VOUT V_OUT
V_IN
R₁
Series
ON/OFF
C_IN
VSS
C_L
GND
Figure 18
18
Seiko Instruments Inc.