EUP2539 datasheet(9/11 Pages) EUTECH

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EUP2539

DS2539

Ver1.1

Apr. 2009

10203040

8090 100

PWM Duty Cycle (%)

0.2

0.4

0.6

0.8

3.5

4.5

Input Voltage (V)

-40℃

-25℃

85℃

125℃

Figure 6. Filtered PWM Dimming Control

Filtered PWM Dimming (0V to 2.5V)

Figure 7.

Open Load Shutdown

In the event of an “Open LED” fault condition, the

EUP2539 will continue to boost the output voltage with

maximum power until the output voltage reaches

approximately 38V. Once the output exceeds this level,

the device will cease operation until the EN pin is cycled

off and on.

Figure 8. Open LED Protection

Shutdown Voltage vs. Input Voltage

Figure 9.

Enable to Open LED Waveforms

Figure 10.

Thermal Shutdown

Thermal overload protection circuitry has been included

to prevent the device from operating at unsafe junction

temperatures above 150ºC. In the event of a thermal

overload

condition

the

device

will

automatically

shutdown and wait till the junction temperatures cools to

130ºC before normal operation is resumed.

Capacitors Selection

A 4.7µF to 10µF ceramic input capacitor (CIN) and a

0.22µF to 4.7µF ceramic output capacitor (COUT) are

sufficient for most applications. During Direct PWM

Dimming

control,

larger

output

capacitor

will

significantly reduce audio noise induced by output

capacitor, and a smaller will enlarge the audio noise, a

2.2uF COUT is recommended. Under normal condition, a

4.7µF input capacitor is sufficient. For applications with

higher output power, a larger input capacitor of 10µF

may be appropriate. X5R and X7R capacitor types are

ideal due to their stability across temperature range.

VEN

2V/div

VOUT

20V/div

50.0µs/div

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