Zxld1360, Application information, A product line of diodes incorporated – Diodes ZXLD1360 User Manual
Page 15: Cont.), Shutdown mode, Soft-start, Actual operating waveforms [v, 15v, r, 1v, l=33µh, 0nf on adj
ZXLD1360
ZXLD1360
Document number: DS33471 Rev. 4 - 2
15 of 25
March 2011
© Diodes Incorporated
A Product Line of
Diodes Incorporated
Application Information
(cont.)
Shutdown Mode
Taking the ADJ pin to a voltage below 0.2V for more than approximately 100µs will turn off the output and supply current to a
low standby level of 20µA nominal.
Note that the ADJ pin is not a logic input. Taking the ADJ pin to a voltage above V
REF
will increase output current above the
100% nominal average value. (See graphs for details).
Soft-start
The device has inbuilt soft-start action due to the delay through the PWM filter. An external capacitor from the ADJ pin to
ground will provide additional 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. With no external
capacitor, the time taken for the output to reach 90% of its final value is approximately 500
μs. Adding capacitance increases
this delay by approximately 0.5ms/nF. The graph below shows the variation of soft-start time for different values of capacitor.
Actual operating waveforms [V
IN
=15V, R
S
=0.1V, L=33µH, 0nF on ADJ]
Soft-start operation. Output current (Ch2) and LX voltage (Ch1)
The trace above shows the typical soft startup time (t
SS
) of 500µs with no additional capacitance added to the ADJ pin.
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