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Rohm Semiconductor Electronic Components Datasheet

BD9478F Datasheet

PWM pulse Generator

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BD9478F
Datasheet
LED Drivers series for LCD Backlights
PWM pulse Generator for
LCD Panels
BD9478F
General Description
BD9478F is PWM pulse generator for LCD panel. This
IC compares triangle waveform which is generated
inside IC and external DC signal, and generates a
PWM pulse. This PWM pulse is provided to LED driver
and controls LED grayscale. PWM pulse frequency
can be synchronized to external signal frequency
inputted to SYNC terminal. Even if this frequency gets
out of range, it works in the setting frequency, is
protected and it always provides stable PWM pulse to
LED driver.
Key Specification
Operating power supply voltage range: 4.5V to 5.5V
Free Run frequency:
150Hz (CT=0.01µF)
Operating Current:
Operating temperature range:
℃ ℃2mA (typ.)
-40 to +85
Applications
LED backlight of monitor, TV, NOTE PC, etc.
Features
The signal that the frequency synchronizes with the
VSYNC signal is output to PWMOUT.
The PWM pulse is generated with the DC signal of a
triangular wave and PDIM generated with the LCT
capacitor.
When the VSYNC frequency exceeds the stipulated
range, it fixes by a set frequency.
(fSYNC<fPLLtyp*0.35 -> fPLL=0.36*fPLLtyp , fSYNC>
fPLLtyp*2.75 -> fPLL=2.75*fPLLtyp)
When VSYNC is a no signal input, the self-oscillation is
operated by set frequency decided on the CT capacitance.
When the pulse signal is input to the terminal EXTPWM,
it shifts automatically to external PWM mode.
Package
SOP-8:
Pin Pitch:
W(Typ.) D(Typ.) H(Max.)
5.00mm x 6.20mm x 1.71mm
1.27mm
Typical Application Circuit
CVCC
VIN
PDIM
fVSYNC
1 VCC
CEXTPWM
Connector CPDIM
CVSYNC
2 EXTPWM
3 PDIM
4 VSYNC
PWMOUT 8
PWM signal out
(to LED driver)
GND 7
CLPF1 CLPF2
LPF 6
RLPF2
CT 5
CCT
Figure 1. SOP-8
Figure 2. Typical Application Circuit
○ :Product structure Silicon monolithic integrated circuit
.www.rohm.com
・ ・© 2012 ROHM Co., Ltd. All rights reserved.
TSZ22111 14 001
This product is not designed protection against radioactive rays
1/12
TSZ02201-0F1F0C100010-1-2
24. Jul.2012 Rev.002


Rohm Semiconductor Electronic Components Datasheet

BD9478F Datasheet

PWM pulse Generator

No Preview Available !

BD9478F
● ℃Absolute maximum ratings (Ta=25 )
Parameter
Symbol
Ratings
Power supply voltage
VCC
7
Operating Temperature Range
Ta(opr)
-40 ~ +85
Storage Temperature Range
Tstg -55 ~ +150
Junction Temperature
Tjmax
Power Dissipation
Pd
*1 Decreases 5.5mW/°C at Ta=25°C or higher (When mounting a one-layer 70.0mmx70.0mmx1.6mm board)
150
6891
Datasheet
Unit
V
°C
°C
°C
mW
● ℃Operating Ratings (Ta = 25 )
Parameter
Power supply voltage
Symbol
VCC
Range
4.5 5.5
Unit
V
VSYNC input frequency range
EXTPWM input PWM signal frequency range
F_VSYNC
F_EXTPWM
0.040 0.8
FCT 30
kHz
kHz
The operating conditions written above are constants of the IC unit. Be careful enough when setting the constant in the actual set.
FCT is dimming frequency that oscillates itself when VSYNC terminal is input no signal
External Components Recommended Range
Item
Symbol
Setting Range
Unit
VCC capacitance
CVCC
0.1 ~ 10
µF
PLL Burst OSC oscillation frequency setting
capacitance
CT
0.040 0.8
µF
The operating conditions written above are constants of the IC unit. Be careful enough when setting the constant in the actual set.
Pin Configuration
Marking diagram and physical dimension
8765
D9478
1234
SOP-8
Figure 3. Pin Configuration
Lot No.
Figure 4. Physical Dimension
www.rohm.com
・ ・© 2012 ROHM Co., Ltd. All rights reserved.
TSZ22111 15 001
2/12
TSZ02201-0F1F0C100010-1-2
24. Jul.2012 Rev.002


Part Number BD9478F
Description PWM pulse Generator
Maker ROHM
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