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.

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.

APPLICATIONs
   LED backlight of monitor, TV, NOTE PC, etc.