Diodes ZXLD1366 - Manual (Page 19)

ZXLD1366
Document number: DS31992 Rev. 8 - 2
19 of 30
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October 2013
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A Product Line of
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ZXLD1366
Application Information
(cont.)
Soft-Start
An external capacitor from the ADJ 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 0.2ms/nF. The graph below shows the variation of soft-start time for different values of capacitor.
Actual Operating Waveforms [V
IN
= 60V, R
S
= 0.2 Ω, L = 68μH, 22nF on ADJ]
Soft-start operation. LX voltage (CH2) and Output current (CH3) using a 22nF external capacitor on the ADJ pin.
60 80 100 120 0 20 40
CAPACITANCE (nF)
Soft-Start Time vs. Capacitance form ADJ to Ground
16
14
12
10
4
2
0
-2
8
6
S
O
F
T
-S
TA
R
T
T
IME
(ms
)