3.REMOTE ON/OFF:
REM
REMONF
trem
REMON
toff
SS
WT7520
Data Sheet Rev. 0.90
trem
toff
4. Under Voltage Protection Delay Time:
REM
REMON
UVP
td,uvp
5. Pulse Width Modulation Block:
The output pulse width modulation is generated by comparision of the saw–tooth waveform
from the capacitor CT to the feedback of the voltage.
Therefore, an increase in feedback control signal amplitude cause a linear decrease of the
output pulse width. Also, the SS(DTC and Soft-Start) limits the output pulse width. The timing
diagram is shown as below:
CT
DTC
FF-CLK
FF-Q
FF-QN
C1
C2
PWM OUT
Weltrend Semiconductor, Inc.
Page 7