ZXSC410/ZXSC420/ZXSC440

Document number: DS33618 Rev. 5 - 2

8 of 17

www.diodes.com

March 2013

© Diodes Incorporated

ZXSC410/ZXSC420/ZXSC440

LED Driving

The ZXSC410/420/440 make simple low voltage boost LED drivers.

The resistor value is determined by the following:

LED

FB

LED

R

V

I



GND

Open-Circuit Protection

As a boost converter if the load (LED chain) should become open-circuit a Zener diode can be connected across the LED chain preventing over-

voltage and possible damage to the main switching transistor. The Zener diodes should be selected by ensuring its voltage rating is higher than

the combined forward voltage of the LED chain. Under open circuit conditions the current in the Zener diode defines the output current as:

Z

FB

Z

R

V

I 

The circuit example below give an open circuit output

current of 300µA.

GND

1k?

ZD1

To

converter