ZLED7010

40V 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 PRELIMINARY and subject to changes

without notice.

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4

Operating Conditions

4.1.

Thermal Conditions

Refer to section 1.1 for maximum package power dissipation specifications for the ZLED7010’s SOP-8

package. Exceeding these specifications due to operating the chip at high ambient temperatures (see section

1.2 for maximum operating temperature range) or driving over the maximum load current (see section 1.3) can

damage the ZLED7010. The ZLED7010 can be used for LED current applications up to750mA when properly

mounted to a high wattage land pattern. Conditions such as operating below the minimum supply voltage or

inefficiency of the circuit due to improper coil selection or excessive parasitic capacitance on the output can

cause excessive chip power dissipation.

4.2.

Thermal Shut-Down Protection

The ZLED7010 includes an on-board temperature sensing circuit that stops the output if the junction exceeds

approximately 160°C.

4.3.

Open-Circuit Protection

The ZLED7010 is inherently protected if there is an open-circuit in the connection to the LEDs because in this

case, the coil is isolated from the LX pin. This prevents any back EMF from damaging the internal switch due

to forcing the drain above its breakdown voltage.

4.4.

External Temperature Compensation of Output Current

The ZLED7010’s temperature compensation feature is useful in applications that require a temperature

compensated LED control current to ensure stability and reliability over temperature, such as high luminance

LEDs. When output current compensation is needed, use an external temperature sensing network, typically

with negative temperature coefficient (NTC) thermistors/diodes, located close to the LED(s) and connected to

output current if the temperature sensing input indicates a rising temperature.

Figure 4.1

Temperature Compensation

GND

ZLED7010

R2

R3

NTC

R4

As shown in Figure 4.1, the temperature compensation curve is determined by R2, R3 (NTC) and R4. When

the LED temperature increases, the resistance of R3 decreases. As R3 reaches the point that R3 plus R4