LA5663V

No.A0003-9/15

Functional Descriptions

(1) IFB and DET_CR pins

The IFB pin connects the CCFL current waveform detected by R10 to the Q4 base with bias VBE. The DET_CR pin

output level depends on both the Q4 base voltage less the VF component and the time constant determined by C4 and

R2. These connections rectify the AC CCFL current waveform (VAC) for input to the negative side of the ERROR

amplifier.

(2) VLOOP_C and PGATE pins

The PWM waveform output from the P_GATE pin is the result of the PWM1 amplifier comparing the VLOOP_C

voltage and the VOC triangular wave so that the rectified CCFL current waveform from the DET_CR pin has the same

potential (0.5V) as the positive side of the ERROR amplifier. This PWM control ensures that the CCFL current remains

constant.