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LMP8646EB: Evaluation board

MASSIMO UBERTI
Prodigy 30 points
Part Number: LMP8646EB
Other Parts Discussed in Thread: LM3102, LMP8646

Hi, I'm working with LMP8646EB evaluation board  suggest from TI engineer Amy Le with his very interest video, anyway connect and test the board  something seem not to work properly.

The problem is that the LM3102 (or LMP8646) do not limiting the current to the super capacitor that goes over his 2.3 volt limit... dangerously !

These are my questions:

1) Are the evaluation board ready to use out of the box with all correct components for the supercap installed ? 

2) Why the User guide suggest to use a second  power supply for the LMP 8646 V+  ( the LM3102  itself provide  the Vcc to LMP8646 via  JP1 )

3) There is need to connect J2 VP ?

Thank you

Massimo

  • 0
    TI__Mastermind 24535 points
    Hello Massimo,

    Thanks for considering to use Texas Instruments.
    1) Typically all our EVMs are supposed to be out of the box ready with all necessary components installed. Do you see any unpopulated footprints on your board?
    2)I believe the person who designed this board wanted to give the user the flexibility of using two different power rails for the devices and therefore included JP1. As for the mention of two supplies in section 1.2, I think the writer meant to say 1 supply was for Vin to LM3102 while the other supply was for the VCC and V+ of the LMP8646 and LM3102.
    3)Unless you connect a supply to TP5 some other part of the trace connecting LM3102 pin 16 and LMP8646 pin 6, it is absolutely necessary that you connect a supply to J2 VP.
  • 0 in reply to Patrick Simmons
    Prodigy 30 points
    Hello Patrick and thank you for your reply.
    This what I found:
    The e2e.ti.com/.../LMP8646EB board are populated but not with correct components. There is only one supercap instead two as manual report. This single supercap has double capacity but different voltage and other component value involve to regulate I believe are not adjust to match the new requirements.

    I changed on the evaluation board the components with I used in my project like supercap and some resistors and in this way everything works fine.

    So for the future everyone want to use LMP8646EB be careful double check or the supercap will go over voltage and blow out in few second.

    Regards
    Massimo