S-8331 Seiko Instruments USA, S-8331 Datasheet - Page 25

• Manufacturer Part Number: S-8331
• Description: Step-Up Switching Regulator (DC/DC Converter ICs)
• Manufacturer: Seiko Instruments USA

Rev.5.1
Application Circuits
1. Large Size LCD Panel Drive Power Supply
This is an output voltage step-up circuit using the S-8331 Series. 30 V or more output voltage, i.e., the
maximum voltage of the S-8330/8331 Series, is available by dividing the output voltage by external
resistors RA and RB and feeding back to V
pin varies by switching the electric volume. Therefore, a small singal NPN transistor (Tr. 3) is needed
between the external voltage dividing resistor and V
The output voltage is represented by equation (18).
This is a circuit example to drive a large size LCD panel (40 V/20 mA) at a 5-V power (5 V±10%).
Pay attention to the following precautions when using this IC.
• Make sure that the switching transistor (Tr.1) and a Schottky diode (SD) have sufficient resistance
• When stopping step-up operation from the step-up operation state using the power off pin, V
• The output voltage fails to stabilize when the output current falls short to 1 mA or less. In this case,
Tr.1:
2SD1624
_00
L
against high output voltage you use. For example, the 2SD1624 manufactured by Sanyo Electric
Co., Ltd. and the MA789 manufactured by Matsushita Electric Industrial Co., Ltd. are used in this
circuit example for a switching transistor and a Schottky diode, respectively.
is short-circuited to V
added to the area between the collector and the emitter of the transistor (Tr. 3). Always use a small
signal transistor which is sufficient enough to withstand high output voltage (Tr. 3).
add a capacitor CF between the output line and the V
capacitor is approx. 0.01 μF. Select the best capacitance after checking it under actual operation
conditions.
Output voltage =
V
V
OUT
BE
: Voltage between the base and the emitter of Tr. 3
: S-8331 V
1kΩ
2200pF
STEP-UP, FOR LCD BIAS SUPPLY, 1-CHANNEL SWITCHING REGULATOR
Figure 18 Large Size LCD Panel Drive Power Supply
OUT
⎛
⎜
⎝
RA
V
EXT
setting voltage
IN
SS
RB
+ RB
by an Nch transistor. Because of this, the output voltage is temporarily
S-8331A30FS
⎞
• ⎟
⎠
V
SS
(V
Seiko Instruments Inc.
SD:
MA789
OUT
ON/OFF
+V
VSTRB
OUT
VCLK
VDIN
V
BE
OUT
)
pin. In the S-8331 Series the internal impedance of V
ZD:15V
OUT
pin to convert the impedance.
OUT
pin. The recommended capacitance of the
Tr.2
(18)
CF
Tr.3
S-8330/8331 Series
RA:
180kΩ
RB:
600k
www.DataSheet4U.com
Ω
+
−
To 40V
F93/
4.7μF×2
OUT
OUT
pin
25