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LP8866-Q1: Adaptive Boost Control Clarification

Part Number: LP8866-Q1


I have a potential application looking to use different LED string lengths on the six outputs of the LP8866-Q1, is that an acceptable use case?  Reading section of the datasheet, my understanding is as follows:

I have two LED strings, one of length 12 and the other of length 6.  The forward voltage of the LEDs in these strings is 3.2V and the forward current is 30mA.  If I connect these two strings to two different outputs of the LP8866-Q1, my understanding is the adaptive boost control will control for the longer length of 12 LED string to maintain a reasonable VHEADROOM.  Assuming a 1V VHEADROOM, the boost voltage would be around (12*3.2)+1 = 39.4V.  In the case of the string with length 6, that would leave (39.4V - (6*3.2))*.03A = 606mW to be dissipated across the OUTx path of the LP8866-Q1. 

Is that understanding correct?  And more importantly, is that an acceptable use case for this component or should all the LED strings be kept at the same length? 

Thank you!

  • Yes, the understanding is correct. As LP8886 driver channels can be tied together in groups of one, two or three, It's recommend to tie OUT4-OUT6 together to dissipate the power consumption. A resistor of 300- 500ohm (0.5- 1W) else in series with this LED string can also help reduce power loss in chip.