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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)

(

*

*

LX

L

S

AVG

LED

IN

ON

R

r

R

I

V

V

I

L

t

+

+

−

−

∆

=

)

(

*

*

L

S

AVG

D

LED

OFF

r

R

I

V

V

I

L

t

+

+

+

∆

=

To ensure stable output current, use a 1% accuracy resistor with adequate power tolerance and a good

temperature characteristic for Rs.

Table 3.1

Nominal Average Output Current (mA)

1200 (maximum for ZLED7020)

0.082

1000 (maximum for ZLED7320)

0.1

750 (maximum for ZLED7520)

0.13

667

0.15

350 (maximum for ZLED7720)

0.27

333

0.3

3.3.2

Inductor L1

The recommended range for the L1 inductor is 33

µH to 220µH. Select the inductor value for L1 as needed to

ensure that switch on/off times are optimized across the load current and supply voltage ranges. If the application

requires a high supply voltage and low output current, inductance values at the high end of this range are recom-

mended to minimize errors due to switching delays, which can reduce efficiency and increase ripple on the output.

(3)

(4)

Where:

Symbol

Description

L

L1 coil inductance in H

I

L1 coil peak-peak ripple current in A (internally set to 0.3

Supply voltage in V

Total forward voltage in V for LED string

Nominal average LED current in A

Rs

External current sense resistor in

L1 coil resistance in

LX switch resistance in

D1 diode forward voltage at the required load current in V