LED DRIVER PR4401/PR4402

Connecting two LEDs in series

It is possible to operate PR4401 and PR4402 with two LEDs in series at the output.

However, while the peak output current is nearly independent of the output load, the mean

output current with two LEDs in series is reduced to half the current with one LED. In

addition, at high output voltages the efficiency drops significantly, depending on operating

conditions, and current pulses become shorter and sharper.

Therefore, although possible and useful in some cases, this operation mode is not

recommended for general applications and not specified further.

Using red, green or yellow LEDs

Although PR4401/PR4402 is optimized for operation with white or blue LEDs, it will usually

also work with red, green or yellow LEDs, with the following restrictions:

a) The LED must build up a sufficient forward voltage to trigger PR4401/PR4402. Due to

the internal resistance of the LED, this condition is usually met. However, no guarantee

can be assumed for proper operation under all conditions, and you need to qualify the

system yourself

b) Due to the different forward voltage level and internal resistance of colored LEDs, the

timing is different, and mean currents are mostly lower than for white LEDs. Also other

parameters may deviate from this data sheet.

© PREMA Semiconductor GmbH 2006-2008

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