• State
  • Locked Locked
  • Replies 4 replies
  • Subscribers 64 subscribers
  • Views 152 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LP8863-Q1: Sepic Capacitor with Additional Polymer Capacitor and Series Resistor.

DAVID SABALESKY
Prodigy 225 points
Part Number: LP8863-Q1
Other Parts Discussed in Thread: LP8868Y-Q1, TPS923654

Tool/software:

Hello Ti Support,

I am using the LP8863-Q1, Sepic configuration, with coupled inductors.

Do I need a Poly Capacitor with Resistor in parallel with the Coupling Capacitor?

A prior design incorporated the PCAP and RES. The datasheet indicates that this is not needed when using a coupled inductor.

I prefer not to add these components due to improved layout without them.

Please advise on the advantages or disadvantages of the PCAP and RES components in the design or omitted, as shown below - red box area. The Coupling Ceramic Capacitor is always in-circuit.

  • 0
    TI__Expert 3551 points

    Hi David,

    Our expert will reply to you later. Thanks for your patience!

  • 0
    Prodigy 225 points

    Thank you Suchen.

    I look forward to the reply. Please see details listed below on usage without BOOST or SEPIC configuration.

    I want to do my due diligence and design for maximum reliability.

    Estimated usage is +10K units, therefore I review all possible options before proceeding to final layout.

    The design has 5 led strips of varying lengths and current requirements.

    I prefer to use a simpler option due to cost of IC and Coupled Inductor. Perhaps LP8863 without BOOST or SEPIC is an option.

    Please advise if this possible or if there are other ICs that will accommodate RGB, 3-channel, outputs with respective current levels as the LP8863.

    The main Led Strip requires 800ma per RGB channel, hence the use of 3 ICs, one for each color, with all 6 outputs connected and paralleled together for max 900ma.

    The other 4 Led Strips require much less current, only 290ma per channel. Each RGB channel is driven from 2 outputs connected together (max 300ma IC).

    The design derives a 24V DC bus from an AC/DC power supply.

    1. Can you utilize the LP8863 without BOOST or SEPIC configuration, while limiting power losses within the IC?

    I would like to use the LP8863 as a simple current regulator for each RGB channel. NO BOOST or SEPIC configuration.

    I understand the LDO function of the LP8863 outputs and the adaptive voltage scaling to reduce power losses.

    Because the led strips are rated for 24V and the power rail is also at 24V, I would like to use the LP8863 as just a current regulator for each RGB channel.

    I am uncertain whether this will increase power consumption in the IC.

    The main led strip still needs one IC per RGB channel, while the other strips can use a single IC, 2 pins paralleled that drive the RGB and channels respectively.

    Please get back to me as soon as possible.

    Sincerely,

    David

  • 0 in reply to DAVID SABALESKY
    TI__Expert 3551 points

    Hi David,

    Our expert is OoO this week. Thanks for your patience.

    To be noted, LP8863-Q1's LED driver cannot work independently. If you are seeking for a high-current LED driver with 24V in and 24V out. LP8868Y-Q1 in Buck-boost configuration could be a choice (TPS923654/5 for non-automotive version).

  • 0 in reply to DAVID SABALESKY
    TI__Mastermind 31505 points

    Hi, David

    Let me summarize your requirement here.

    • Major led string, 800mA per channel, total 3channel.
    • other LED string, 290mA per channel, total 12 channel(4*3).
    • For all the string, VF is the same 24V or not? Normally Vf for RGB is different.

    May I understanding correct?

    Looks like you needs a liner device and directly connect to the input voltage. Maybe you could look at the TPS69627, 100mA per channel, total 48ch device.