Diodes AP8802H - Manual (Page 10)

AP8802H
60V 1A LED STEP-DOWN CONVERTER
AP8802H
Document number: DS32227 Rev. 6 - 2
10 of 14
www.diodes.com
May 2012
© Diodes Incorporated
PRELIMINARY
NEW PROD
UC
T
Applications Information (cont.)
Soft-Start
An external capacitor from the CTRL pin to ground will provide a soft-start delay, by increasing the time taken for the voltage on this pin to
rise to the turn-on threshold and by slowing down the rate of rise of the control voltage at the input of the comparator. Adding capacitance
increases this delay by approximately 200µs/nF. The graph below shows the variation of soft-start time for different values of capacitor.
0 120 20 100 40 60 80
S
O
F
T
-S
T
A
R
T
T
IM
E
(
m
s
)
CAPACITANCE (nF)
Soft Start Time vs. Capacitance from ADJ Pint to Ground
16
-2
14
0
2
4
12
10
8
6
Thermal Considerations
The graph below in Figure 19, gives details for power derating. This assumes the device to be mounted on a 25x25mm PCB with 1oz
copper standing in still air.
-40 -25 5 -10 20 35 50 80 65 95 110 125
AMBIENT TEMPERATURE (°C)
Maximum Power Dissipation
Figure. 19 AP880H Derating Curve
P
O
WE
R
DI
SSI
P
A
T
IO
N (
W
)
2.5
2
1.5
1
0.5
0