ZLED7020

High Current 40V LED Driver with Internal Switch

Data Sheet

August 12, 2011

© 2011 Zentrum Mikroelektronik Dresden AG — Rev. 1.2

All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without

the prior written consent of the copyright owner. The information furnished in this publication is subject to changes without notice.

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2.4

Control of Output Current via a PWM Signal on the ADJ Pin

An external pulse width modulation (PWM) control signal input on the ADJ pin can be used for brightness or gated

on/off control of the output current by driving the output current to a value below the nominal average current

within the range of 0 to 5 V. The logic high level must be higher than 1.2V and the logic low level must be below

2.5

Control of Output Current via a Microcontroller Signal on the ADJ Pin

An external control signal from the open drain output of a microcontroller can provide on/off or PWM brightness

control by driving the ADJ pin. See Figure 3.4 for a typical application circuit. Diode D2 and resistor R1 shown in

Figure 3.4 suppress any negative high-amplitude spikes on the ADJ input due to the drain-source capacitance of

the FET in the microcontroller’s output. Negative spikes on the ADJ input could cause output current errors or

unintended ZLED7x20 operation. The signal input to the ADJ pin must be capable of driving the ADJ pin’s input

2.6

Shutdown Mode

will switch the output back to full operational mode.

2.7

ZLED7x20 Protection Features

2.7.1

Thermal Shut-down Protection

The ZLED7x20 automatically protects itself from damage due to over-temperature conditions. If the ZLED7x20’s

thermal considerations.

2.7.2

LED Open Load Protection

As a step-down converter, the ZLED7x20 has inherent open-load circuit protection. Since the L1 inductor is

connected in series with the LED string, the current flow is interrupted if the load is open and the LX output of the

ZLED7x20 will not be damaged. This provides an advantage over other products such as boost converters, for

which the internal switch can be damaged by back EMF forcing the drain above its breakdown voltage.