S-817 Seiko Instruments, S-817 Datasheet - Page 15

• Manufacturer Part Number: S-817
• Description: Super Small Package CMOS Voltage Regulator
• Manufacturer: Seiko Instruments

Rev.3.0
To stabilize operation against variation in output load, a capacitor (C
and VSS in the S-817 series because the phase is compensated with the help of the internal phase
compensation circuit and the ESR of the output capacitor.
When selecting a ceramic or an OS capacitor, capacitance should be 0.1 µF or more, and when selecting a
tantalum or an aluminum electrolytic capacitor, capacitance should be 0.1 µF or more and ESR 30 Ω or
less.
When an aluminum electrolytic capacitor is used attention should be especially paid to since the ESR of the
aluminum electrolytic capacitor increases at low temperature and possibility of oscillation becomes large.
Sufficient evaluation including temperature characteristics is indispensable.
characteristics differ depending upon the type of the output capacitor.
Reference Data 1. Transient Response Characteristics”.
Selection of Output Capacitor (C
Application Circuits
1. Output Current Boosting Circuit
As shown in Figure 14, the output current can be boosted by externally attaching a PNP transistor. The
base current of the PNP transistor is controlled so that output voltage (V
in the S-817 Series when base-emitter voltage (V
between input voltage (V
The following are tips and hints for selecting and ensuring optimum use of external parts
_00
• PNP transistor (Tr1):
• Resistor (R
• Output capacitor (C
• Resistor (R
• DO NOT attach a capacitor between the S-817 Series power source (V
• To improve transient response characteristics of the output current boosting circuit shown in
• Pay attention to the short current limit circuit incorporated into the S-817 Series because it does
between base and emitter of the PNP transistor to avoid oscillation.
Figure 14, check that no problem occurs due to output fluctuation at powering on or due to
power or load fluctuation under normal operating conditions.
not function as a shortcircuiting protection circuit for this boosting circuit.
1. Set h
2. Confirm that no problem occurs due to power dissipation under normal operation conditions.
Generally set R
Output capacitor (C
or load fluctuation, but oscillation might occur. Always connect resistor R2 in series to output
capacitor C
FE
1
2
):
): Set R
to approx. 100 to 400.
L
.
1
IN
to 1 kΩ ÷ V
L
2
GND
):
V
) and S-817 Series power source pin (VIN).
to 2 Ω × V
L
IN
SUPER-SMALL PACKAGE CMOS VOLTAGE REGULATOR
) is effective in minimizing output fluctuation at powering on or due to power
C
IN
R
OUT (S)
Seiko Instruments Inc.
OUT(S)
L
1
)
Tr1
(the voltage specified in the S-817 Series) or more.
or more.
VIN
Figure 14
BE
VSS
S-817
series
) necessary to turn on the PNP transistor is obtained
VOUT
L
) must be mounted between VOUT
R
C
2
Refer to C
L
OUT
V
Overshoot and undershoot
) goes the voltage specified
OUT
IN
) and GND pins or
L
dependencies in “
S-817 Series
15