AP3842 datasheet(6/8 Pages) ANACHIP

6 / 8 page

High Performance Current Mode PWM Controller

AP3842/3/4/5

Anachip Corp.

www.anachip.com.tw

Rev.1.0 Oct.11, 2004

6/8

Shutdown of the AP3842 can be accomplished in two ways; either raise pin 3 above 1V or pull pin 1 below a

voltage two diode drops above ground. Either one of them causes the output of the PWM comparator to be

high (refer to block diagram). The PWM latch is reset dominant so that the output will remain low until the

next clock cycle after the shutdown condition at pins 1 and/or 3 is removed. In one example, an externally

latched shutdown may be accomplished by adding an SCR that will be reset by cycling Vi below the lower

UVLO threshold. At this point the reference turns off, allowing the SCR to reset.

Figure 7 : Slope Compensation.

Uref

RT/CT

Isense

Rsense

Isense

0.1uF

AP3842/3

A fraction of the oscillator ramp can be resistively summed with the current sense signal to provide slope

compensation for converters requiring duty cycles over 50%. Note that capacitor, C, forms a filter with R2 to

suppress the leading edge switch spikes.

AP3842 Folha de dados(PDF) 6 Page - Anachip Corp