ZLED7330

High Current 40V LED Driver with Switch Dimming

Data Sheet

August 16, 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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Rs

V

1

.

0

I

Rs

V

1

.

0

K

I

X

dim

OUT

∗

=

2

Circuit Description

2.1

ZLED7x30 Overview

The ZLED7x30 is a continuous-mode inductive step-down converter LED driver for driving single or multiple

series-connected LEDs from a voltage input higher than the LED voltage (Vin = 8.5 to 40VDC; see section 3.2.2

for important details). The ZLED7x30 provides an adjustable output current (1.2A maximum for ZLED7030; 1.0A

maximum for ZLED7330; 0.75A maximum for ZLED7530; 0.35A maximum for ZLED7730) , which is nominally set

via an external sense resistor Rs and controlled by the ZLED7x30’s integrated high-side output current-sensing

circuit and output switch. The ZLED7x30 detects external switching action on the supply line to adjust the output

current in different modes on different levels.

Only a resistor, a diode, an inductor, and three capacitors are needed for a typical basic application. Refer to the

application circuits in section 3 for the location of the components referred to in the following sections.

2.2

Control of Output Current via External Sense Resistor Rs

mended values for Rs in a typical basic application and section 3.4 for layout guidelines for Rs.

(1)

2.3

Multi-Mode Switch Dimming

The ZLED7x30 detects external switching action on the supply line to adjust output current, allowing dimming

functionality to be achieved without changing the original lighting system circuitry. The switch dimming is imple-

mented in either two-level mode or three-level mode. The output current of each level and the total number of

levels are customer selected by setting the corresponding input conditions on the DIM1 and DIM2 pins. See

page 2 for a typical application using the DIM1 and DIM2 pins.

The output current is set at the initial 100% value determined by the sense resistor Rs the first time that power is

supplied to the chip. After the initial power up sequence, the chip adjusts the output current according to the

external switch action. After the lowest current level, the current cycles back to the initial value if subsequent

switch action is detected. If the power is switched off for longer than 2 seconds, the device will return to its initial

state and the output current will be set to the initial value the next time that power is applied.

There are two types of switch action: a normal switch, which has an off-time between each subsequent switch

action longer than 2s, and a dimming switch, which has an off-time between each subsequent switch less than 2s.

The dimmed average output current is given by

(2)

Where