S-8355 Seiko Instruments, S-8355 Datasheet - Page 31

• Manufacturer Part Number: S-8355
• Description: (S-8355 - S-8358) PWM/PFM SWITCHING CONTROL STEP-UP SWITCHING REGULATOR
• Manufacturer: Seiko Instruments

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Rev.6.6
STEP-UP, SUPER-SMALL PACKAGE, 600 kHz, PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
4.2 Bipolar (NPN) Type
A circuit example using the CPH3210 (h
(NPN) is shown in Figure 20 to 25 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 19 .
*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 E, G, J, K, L, M, P and Q type,
_00
DD
b
value is calculated according to
for E, G, J, K, L, M, P and Q types.
b
b
b
value can increase the output current, but the efficiency decreases. Since a current may flow on the
value should be determined by experiment.
value after performing sufficient evaluation since the optimum C
FE
) using
b
value is around 1 k
I =
b
h
I
PK
FE
Figure 19 External Transistor Peripheral Circuit
, and select the smaller R
Pch
Nch
R
Seiko Instruments Inc.
b
C
b
) in parallel with the R
b
FE
=
Ω
≤
VOUT
V
. Actually, calculate the necessary base current (I
= 200 to 560) from Sanyo Electric Co., Ltd. As a bipolar transistor
2
DD
π
I
Standard Circuits ”. The h
b
•
−
*1
R
0
EXT
7 .
b
•
1
−
f
osc
I
0
EXTH
•
2200 pF
4 .
0
1 kΩ
7 .
R
C
.
b
b
.
b
resistance as shown in Figure 19 , decreases
b
value than
I
PK
FE
b
value and R
value differs depending upon the
S-8355/56/57/58 Series
R
b
=
V
b
OUT
value of the bipolar
I
b
b
−
) from the bipolar
0
7 .
−
I
0
EXTH
4 .
31
*1
.