ZXLD1356 datasheet(6/29 Pages) DIODES

6 / 29 page

ZXLD1356

Document number: DS33470 Rev. 3 - 2

6 of 29

www.diodes.com

December 2010

A Product Line of

Diodes Incorporated

Device Description (Continued)

Switching thresholds

With VADJ = VREF, the ratios of R1, R2 and R3 define an average VSENSE switching threshold of 200mV (measured on the ISENSE

pin with respect to VIN). The average output current IOUTnom is then defined by this voltage and RS according to:

IOUTnom = 200mV/RS

Nominal ripple current is ±30mV/RS

Adjusting output current

The device contains a low pass filter between the ADJ pin and the threshold comparator and an internal current limiting resistor

(50k

Ω nom) between ADJ and the internal reference voltage. This allows the ADJ pin to be overdriven with either DC or pulse

signals to change the VSENSE switching threshold and adjust the output current.

Details of the different modes of adjusting output current are given in the applications section.

Output shutdown

The output of the low pass filter drives the shutdown circuit. When the input voltage to this circuit falls below the threshold

(0.2V nom.), the internal regulator and the output switch are turned off. The voltage reference remains powered during

shutdown to provide the bias current for the shutdown circuit. Quiescent supply current during shutdown is nominally 60µA and

switch leakage is below 5µA.

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