LP8866-Q1: Control Current on each channel separately over i2c interface

Benjamin Vespone

Part Number: LP8866-Q1
Other Parts Discussed in Thread: LP8866EVM, LP8863-Q1, LP5569,

Hello,

I'm evaluating with LP8866EVM for a single high current LED application that requires precise brightness control that does not rely on PWM dimming. My intent was to combine 5 channels on the LP8866 to achieve the 1000mA current that I require, and use the 12bit current control registers to change the total effective current. In evaluating the sample, it appears that the programming interface only allows a global control over channel current, meaning that even if I combine all channels together, effective resolution is still only 12bits. Am I missing something here? If not, can anyone recommend a different part number that can provide high resolution current control for up to 1000mA @ <3V (single LED).

Thanks,
Ben

over 3 years ago

0 Charles-Chen over 3 years ago

TI__Genius 11836 points

Hi Ben,

You can use analog dimming with PWM input for 16bit.

0 Benjamin Vespone over 3 years ago in reply to Charles-Chen

Prodigy 120 points

Hi Charles,

Thank you for the response. I am wondering if channels can be controlled individually. I only see global dimming.

-Ben

0 Charles-Chen over 3 years ago in reply to Benjamin Vespone

TI__Genius 11836 points

Hi Ben,

For independent control of each channel, you can choose LP8863-Q1

0 Benjamin Vespone over 3 years ago in reply to Charles-Chen

Prodigy 120 points

Hi Charles,

Thank you for that suggestion. In looking at the datasheet, it appears that if I choose the LP8863-Q1, I would lose the dedicated analog dimming feature. The LP8863 has a 'hybrid' dimming, which utilizes PWM at low currents and analog dimming at high currents. My design goal is a high resolution pure analog dimming control. We've done this in the past with a high resolution digipot on the input of a resistor-set-point based constant current driver. I can do this again, but was hopeful for a more integrated solution.

Any other suggestions?

Thanks,
Ben

0 Charles-Chen over 3 years ago in reply to Benjamin Vespone

TI__Genius 11836 points

Hi Ben,

Actually, I can't understand the resistor-set-point based constant current driver. What's the device of it?

0 Benjamin Vespone over 3 years ago in reply to Charles-Chen

Prodigy 120 points

After looking back at the schematic, it's not actually a digipot, it's an dedicated 12bit DAC feeding the SET pin of a constant current driver that was designed for a voltage divider to determine set point.

https://www.analog.com/en/products/ad5621.html#product-overview

going to SET pin of

https://www.analog.com/en/products/lt3092.html

I would imagine something similar is happening inside these integrated LED drivers that are programmable over i2c.

I'm really looking for something like the LP5569, with a much higher current capacity, and preferably 12 bit current control (vs 8 bit on the LP5569).

Thanks,

Ben

0 Charles-Chen over 3 years ago in reply to Benjamin Vespone

TI__Genius 11836 points

Hi Ben,

I don't under stand your requirement now. The lp8866-q1 is totally different from the LP5569. And LP5569 is not an automotive part. What do you need actually? What's your target application?

0 Charles-Chen over 3 years ago in reply to Charles-Chen

TI__Genius 11836 points

Hi Ben ,

Do you have any feedback for this question?

0 Charles-Chen over 3 years ago in reply to Charles-Chen

TI__Genius 11836 points

Hi Ben,

I will close this thread temporarily since I haven't received your feedback yet. You can keep asking questions in this thread if you have any more questions.

0 Benjamin Vespone over 3 years ago in reply to Charles-Chen

Prodigy 120 points

Hi Charles.

Ok to close thread.

Thanks,
Ben

Power management

Power management forum

LP8866-Q1: Control Current on each channel separately over i2c interface