ZXLD1350Q(2014) 데이터 시트보기 (PDF) - Diodes Incorporated.

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ZXLD1350Q
(Rev.:2014)

AUTOMOTIVE GRADE 350mA BUCK LED DRIVER

Diodes Incorporated. 

A Product Line of

Diodes Incorporated

ZXLD1350Q

Application Information (Continued)

Output Current Adjustment by PWM Control

Directly driving ADJ input

A Pulse Width Modulated (PWM) signal with duty cycle DPWM can be applied to the ADJ pin, as shown below, to adjust the output current to

a value above or below the nominal average value set by resistor RS:

VADJ

PWM

ADJ ZXLD1350

0V

GND

GND

Driving the ADJ input via open collector transistor

The recommended method of driving the ADJ pin and controlling the amplitude of the PWM waveform is to use a small NPN switching

transistor as shown below:

PWM

ADJ ZXLD1350

GND

GND

This scheme uses the 200k resistor between the ADJ pin and the internal voltage reference as a pull-up resistor for the external transistor.

Driving the ADJ input from a microcontroller

Another possibility is to drive the device from the open drain output of a microcontroller. The diagram below shows one method of doing this:

MCU

10k

ADJ ZXLD1350

GND

The diode and resistor suppress possible high amplitude negative spikes on the ADJ input resulting from the drain-source capacitance of the

FET. Negative spikes at the input to the device should be avoided as they may cause errors in output current, or erratic device operation.

PWM dimming can be further split into high frequency and low frequency PWM dimming and how the device responds to these.

ZXLD1350Q

Document number: DS37076 Rev. 1 - 2

11 of 19

www.diodes.com

December 2014

© Diodes Incorporated

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