AP3845S8 Anachip Corporation, AP3845S8 Datasheet - Page 6

• Manufacturer Part Number: AP3845S8
• Description: High Performance Current Mode PWM Controller
• Manufacturer: Anachip Corporation

High Performance Current Mode PWM Controller
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 V
UVLO threshold. At this point the reference turns off, allowing the SCR to reset.
Figure 7 : Slope Compensation.
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 R
suppress the leading edge switch spikes.
Anachip Corp.
www.anachip.com.tw
RT/CT
Isense
Uref
8
4
3
0.1uF
CT
RT
R1
C
R2
6/8
Isense
Rsense
AP3842/3
AP3842/3/4/5
i
Rev.1.0 Oct.11, 2004
below the lower
2
to