ZLED7015

1.0MHz Boost Converter with Internal 35V Switch

Data Sheet

December 20, 2011

© 2011 Zentrum Mikroelektronik Dresden AG

— Rev. 1.00

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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S

S

FB

OUT

R

V

R

V

I

3

.

0





2

Circuit Description

The ZLED7015 is a constant-current boost converter that can also function as a constant voltage driver for

LED applications. The boost converter topology features an internal 35V power switch and feedback circuit to

control the output to the LED string. Optimal performance is achieved by operating in continuous conduction

mode within the application’s load current range; i.e., the current through inductor L1 is always above 0A. The

output current is set by an external resistor and the device supports DC linear or PWM dimming. Additional

device features include selectable open-load/over-voltage protection, over-temperature protection, under-

voltage lockout, and an automatic soft-start function to minimize the inrush current during startup.

2.1

EN Pin, VP Pin, and Soft-Start Function

The EN pin can be used to enable or disable the ZLED7015. When the voltage on the EN pin rises above the

The Z

LED7015’s internal “soft-start” function ensures a smooth device start-up by preventing excessive in-

rush current and providing a controlled rise in the output current. When the soft-start function is initiated, the

internal circuitry clamps the internal switch current threshold to zero during a 1millisecond delay. The soft-start

function then gradually increases the internal switch current threshold over a 4-5 msec period. See Figure

1.11 for an illustration of typical waveforms during start-up.

Important: The EN pin requires termination. If the EN pin is not used to control operation, connect it to the

positive power supply through a 100k

Ω resistor. Do not allow the EN pin to float.

The VP pin is connected to the

ZLED7015’s internal power regulator and requires an external bypass capa-

2.2

Output Current Control

shown on page 2), and the duty cycle of the internal power switch is adjusted to reduce or increase the output

section 3. Dimming can be controlled by superimposing a DC or filtered pulse-width modulated (PWM) signal

2.2.1

(1)

Where