S-8352 Seiko Instruments, S-8352 Datasheet - Page 21

• Manufacturer Part Number: S-8352
• Description: (S-8351 / S-8352) SMALL PACKAGE PFM CONTROL STEP-UP SWITCHING REGULATOR
• Manufacturer: Seiko Instruments

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Rev.2.0
4.2 Bipolar (NPN) Type
STEP-UP, SUPER-SMALL PACKAGE, PFM CONTROL SWITCHING REGULATOR / SWITCHING REGULATOR CONTROLLER
A circuit example using the CPH3210 (h
(NPN) is shown in Figure 24 to 26 in the “
transistor determine the driving capacity to increase the output current using a bipolar transistor. A peripheral
circuit example of the transistor is shown in Figure 20 .
*1. V
The recommended R
transistor (h
A small R
pulse and the voltage may drop due to wiring resistance or other factors in the actual circuit, therefore the
optimum R
Connecting the speed-up capacitor (C
switching loss and improves the efficiency.
The C
Select a C
characteristics of the bipolar transistor.
*1. For D type,
_00
DD
b
value is calculated according to
for D type.
b
b
b
value can increase the output current, but the efficiency decreases. Since a current may flow on the
FE
value should be determined by experiment.
value after performing sufficient evaluation since the optimum C
) using
R
b
=
V
b
I =
b
DD
value is around 1 k
I
−
b
h
I
PK
0
FE
7 .
, and select the smaller R
−
Figure 20 External Transistor Peripheral Circuit
I
0
EXTH
4 .
Pch
Nch
Seiko Instruments Inc.
.
b
C
) in parallel with the R
b
FE
Ω
≤
VOUT
. Actually, calculate the necessary base current (I
= 200 to 560) from Sanyo Electric Co., Ltd. as a bipolar transistor
2
π
Standard Circuits ”. The h
•
*1
R
EXT
b
•
1
f
osc
b
value than
•
2200 pF
0
1 kΩ
7 .
R
C
b
b
.
b
resistance as shown in Figure 20 , decreases
R
b
=
V
I
PK
OUT
FE
I
b
b
−
value and R
value differs depending upon the
0
7 .
−
S-8351/8352 Series
I
0
EXTH
4 .
b
*1
value of the bipolar
.
b
) from the bipolar
21