CM3842/3843
CURRENT MODE PWM CONTROLLER
APPLICATION INFORMATION (continued)
1K
VREF
COMP
330Ω
Shutdown
ISENSE
500Ω
Shutdown
To Current
Sense Resistor
Fig. 5. Shutdown Techniques - there are two ways to shutdown the PWM controller: 1) raise the voltage at
ISENSE above 1V or, 2) pull the COMP below a voltage two diodes above ground.
VREF
RT/CT
ISENSE
0.1µF RT
CT
R2
R1
C
ISENSE
RSENSE
Fig 6. Slop Compensation – To achieve duty cycles over 50% for some applications , the above
slope compensation technique is suggested by resistively summing a fraction of the
oscillator ramp with the current sense signal.
2001/06/27 Advanced
Champion Microelectronic Corporation
Page 7