ZXLD1320DCATC View Datasheet(PDF) - Zetex => Diodes

Part Name

Description

MFG CO.

ZXLD1320DCATC

Buck mode DC-DC converter for LED driving with 1.5A output and current control

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ZXLD1320

Fig 1

PWM control

A wider dimming range can be achieved by applying a PWM control signal to the ADJ pin to turn

the device on and off, giving an average output current proportional to the duty cycle of the

control signal. The ADJ pin can be driven directly from the open drain NMOS output of a

microcontroller, or indirectly with a low saturation voltage NPN transistor such as the Zetex

ZXTN25020DFL. (Fig 2).

ZXTN25015DFL

ADJ

ZXLD1320

Fig 2

In the circuit of Fig 4, the average LED output current will be

I LED (avg) = ILED (nom) * D

Where duty cycle

D = T2

(T1+ T 2)

A PWM frequency of 200Hz, or lower is recommended, to minimize errors due to the rise and fall

times of the converter output.

Issue 1 - January 2008

12

© Zetex Semiconductors plc 2008

www.zetex.com

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