zxld1360 Zetex Semiconductors plc., zxld1360 Datasheet - Page 17

• Manufacturer Part Number: zxld1360
• Description: 1a Led Driver With Internal Switch
• Manufacturer: Zetex Semiconductors plc.

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 will fall 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
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 500µs. 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
Soft-start operation. Output current (Ch2) and LX voltage (Ch1)
The trace above shows the typical soft startup time (Tss) of 500 Sec with no additional
capacitance added to the ADJ pin.
Issue 1 - March 2007
© Zetex Semiconductors plc 2007
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ZXLD1360
www.zetex.com
REF
will increase