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LP5868: Powering LP5868T from 3.7V lithium ion battery

Cyrus Hazari
Prodigy 60 points
Part Number: LP5868

Hi,

I would like to have an LP5868T driving several laser diodes in an enclosure that is free of any external power cables.

So I would like a 3.7V Lithium Ion battery embedded with the 5868T and laser diodes to power everything, and when it runs out of juice, be recharged by plugging in a USB power cable.

In the simplest design, TI components are used to provide charging circuitry for the battery, and as soon as the USB cable is plugged in, the battery begins to charge without causing any damage or loss of continued light emission by the laser diodes. In other words, I can "hot" connect and disconnect charging power from USB without interrupting the output of the laser diodes.

The laser diodes require 3V of DC supply.

Can you provide a TI component list and design guides/application notes?

Thanks,

Cyrus

  • 0
    TI__Expert 6440 points

    Hi Cyrus,

    Nice to hear you.

    I have some questions for your application:

    1) Does the 3.7V power supply for LED and LP5868T will drop below 3.7V during battery running time?

    2) How many current you need for laser diodes? Because the forward voltage of LED will be affected by the current. Besides, the saturation voltage of LP5868 current sink will be affected by the current value. For example, if the current be set to 100mA, I think the forward voltage of lase diodes will be around 3.4V and the saturation voltage will be 0.7V, considering the voltage drop on wire, the 3.7V power supply is not enough for powering the laser diodes.

    3) What kind of design guide/AN you need from TI? example for LP5868T or example LP5868T + charger?

    Thanks!

    Ives Li