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PR4401 Datasheet(PDF) 6 Page - List of Unclassifed Manufacturers |
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PR4401 Datasheet(HTML) 6 Page - List of Unclassifed Manufacturers |
6 / 12 page LED DRIVER PR4401/PR4402 Influence of the LED Forward Voltage measured with 1 LED / 2 LEDs in parallel; Vcc = 1.5V Circuit LED Peak Forward Voltage LED Mean Current Mean Supply Current Efficiency 10 µH, 1 LED 5.8 V 20 mA 70 mA 77 % 10 µH, 2 LEDs || 4.6 V 24 mA 70 mA 80 % 22 µH, 1 LED 4.2 V 13 mA 33 mA 82 % 22 µH, 2 LEDs || 3.5 V 14 mA 32 mA 82 % Peak forward voltages above approx. 5V are often considered as an overload condition and may lead to a lower LED efficiency. Application Notes Selection of PR4401 and PR4402 The circuit type should be selected according to the required LED current. PR4401 is best operated with inductors between 10 and 22µH. PR4402 is best operated with inductors between 4.7 and 10µH. Using lower inductances may lead to erratic behaviour, especially at low supply voltages and should be avoided. Operating with higher inductances is possible and will lead to lower supply and LED current. However the quiescent current which is independent of the inductance will lead to a lower overall efficiency. Since PR4402 has about twice the quiescent current of PR4401, it is not recommended for small LED currents. LED compatibility It must be considered that the peak current through the LED is a factor of up to 7 higher than the mean current. LED lifetime may be affected if operated outside the range specified by the LED vendor. Since the emission spectrum of white LEDs usually depends on the current, the light color may shift to blueish white. High peak currents may also saturate the LED and reduce the light efficiency of the LED. If the rated LED peak current is exceeded, it is recommended to use a smoothing capacitor and diode to provide a continuous output current (see below). With most standard LEDs, this will improve the overall performance with inductors of 10µH and less, or mean output currents of 23mA and more. Note that with especially with the higher currents of PR4402 the current rating of most standard LEDs is exceeded, and more powerful or multiple LEDs must be used. Inductor compatibility While the series resistance of the coil has a small impact on the LED current, it is important that the saturation current is higher than the maximum peak current over the supply voltage range. Inductors optimized for DC-DC converters are mostly suitable. © PREMA Semiconductor GmbH 2006-2008 Page 6/12 Rev 0908 |
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