LED Drivers series for LCD Backlights
PWM pulse Generator for
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
Operating power supply voltage range: 4.5V to 5.5V
Free Run frequency:
Operating temperature range:
℃ ℃2mA (typ.)
-40 to +85
LED backlight of monitor, TV, NOTE PC, etc.
■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
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.
W(Typ.) D(Typ.) H(Max.)
5.00mm x 6.20mm x 1.71mm
●Typical Application Circuit
PWM signal out
(to LED driver)
Figure 1. SOP-8
Figure 2. Typical Application Circuit
○ ：Product structure Silicon monolithic integrated circuit
・ ・© 2012 ROHM Co., Ltd. All rights reserved.
TSZ22111 14 001
○This product is not designed protection against radioactive rays
24. Jul.2012 Rev.002