ZLED7001

Universal LED Driver with Temperature Compensation

Data Sheet

August 12, 2010

© 2010 Zentrum Mikroelektronik Dresden AG — Rev. 1.1

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.

10 of 15

A group of modules based on the ZLED7001 can be matched in LED brightness using the linear dimming

input with the PWM dimming feature still available for overall brightness control.

If the LD pin is not used, it must be connected to the PWMD pin, which is internally pulled-up. When the LD

pin voltage drops below 50mV, the GATE output is switched off.

2.8.

Temperature Compensation

ZLED7001 provides thermal protection for the connected LEDs. Applying an NTC thermistor close to the LED

string will enable the temperature compensation of the LED current. Refer to the application circuit on page 2.

If the temperature of the LEDs rises, the resistance of the NTC thermistor decreases until the voltage of the

LD pin falls below 240mV. Then the average current is controlled by the LD pin and the temperature

compensation function starts. The upper threshold to start compensation is given by equation (5):





















1

R

R

R

V

mV

240

~

V

NTC

NTC

REF

LDH

(5)

inductor current ripple, the temperature compensated continuous current can be computed as shown in

equation (6):

































1

R

R

R

R

15

.

1

V

I

NTC

NTC

S

REF

OUT

(6)

When the LD pin voltage drops below 50mV (typical), the GATE output is switched off. The transition to

dimming as well as the switch-off is reversible as soon as the respective thresholds are exceeded after the

LED assembly cools. Adding a capacitor C1 from the LD pin to ground will reduce noise on the LD input.

2.9.

Design Example

A common application for an AC-line-powered ZLED7001 is luminants with a string of several LEDs operated

by one driver. For the example, the following constraints are assumed:

Application:

15W LED luminant with 13 HB LEDs in 1 string

AC supply voltage:

Average DC supply voltage:

capacitor; power factor correction is not considered.

LED string forward voltage:

LED string average current:

For a given 2N60 MOSFET and a maximum expected switching frequency of 100kHz, the IC input current will

be



mA

kHz

nC

mA

f

Q

mA

I

S

G

IN

4

.

1

)

100

9

(

5

.

0

5

.

0













