Diodes AP3039 - Manual (Page 14)

BOOST CONTROLLER AP3039
Data Sheet
14
BCD Semiconductor Manufacturing Limited Jun. 2010 Rev. 1. 6
Application Information (Continued)
Soft Start
AP3039 has a soft start circuit to limit the inrush
current during startup. The time of soft start is
controlled by an internal 12
µA current source and an
external soft start capacitor C
SS
connected from SS pin
to GND (see Figure 20). The effective C
SS
voltage for
Soft Start is from 0 to 2.3V, the time of Soft Start is:
t
SS
= C
SS
*2.3V/12 µA
VCC Pin Application Description
The AP3039 includes an internal low dropout linear
regulator with the output pin VCC. This pin is used to
power internal PWM controller, control logic and
MOSFET driver. On the condition that V
IN
≥8.5V, the
regulator generates a 6V supply. If 6V ≤V
IN
≤8.5V, the
V
CC
is equal to V
IN
minus drop voltage across bypass
switch. When V
IN
is less than 6V, connect VCC to
VIN.
Typical Application
Figure 20. Application Circuit 1 of AP3039 (Note 2)
OUT
CS
OV
VIN
UVLO
RT
SS
COMP SHDN
EN
FB
GND
C
IN
R
C
C
C
R
T
R2
R1
OFF ON
C
SS
R3
R
CS
R4
C
OUT
OFF ON
V
IN
: 6V to 27V
VCC
C
V
U1 AP3039
Q1
D1
R5
R6
L V
OUT