ZLED7010 datasheet(11/24 Pages) ETC2

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ZLED7010

40V LED Driver with Temperature Compensation

Data Sheet

August 12, 2010

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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2.3.2.

PWM Control

The output current on LX can be set to a value below the nominal average value determined by resistor RS by

using an external PWM signal as the control signal applied to the ADJI pin. This control signal must be

capable of driving the ZLED7010’s internal 500kΩ pull-up resistor. See Figure 2.1 for an illustration. The

minimum signal voltage range is 0V to 1.8V; the maximum voltage range is 0V to 5V. See section 1.3 for the

specifications for the signal’s duty cycle DPWM. Any negative spikes on the control signal could interfere with

current control or proper operation of the ZLED7010.

Figure 2.1

Directly Driving ADJI Input with a PWM Control Signal

ADJ

OUT

079





ZLED

GND ADJO

7010

ADJI

1.8V to 5V

PWM

2.3.3.

External DC Voltage Control of Output Current

The output current on LX can be set to a value below the nominal average value determined by resistor RS by

using an external DC voltage VADJ (0.3 V ≤ VADJ ≤ 1.2V) to drive the voltage at the ADJI pin. This allows

adjusting the output current from 25% to 100% of IOUTnom. See Figure 2.2 for an illustration. The output current

can be calculated using equation (2). If VADJ matches or exceeds VREF (1.2V), the brightness setting is

clamped at its maximum (100%).

Figure 2.2

External DC Control Voltage at ADJI Pin

ADJI

ADJO

GND

ZLED7010

(2)

Where

IOUT_DC = Nominal average output current through the LED(s) with a DC control voltage

VADJ = External DC control voltage: 0.3V ≤ VADJ ≤ 1.2V

RS ≥0.13Ω

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