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LP8758-B0: LP8758-B0 / Guideline of parasitic inductance and resistance from VOUT to load at remote sense

S.Satoshi
Guru 21685 points
Part Number: LP8758-B0

Hi,

Please let me ask the guideline of parasitic inductance and resistance from VOUT to load at remote sense. I'm asking this because the customer evaluate the remote sense function by connecting load board with lead wire, then the output voltage is oscillated with no load. So they'd like to know the guideline of parasitic inductance and resistance from VOUT to load to design their test board from now.

I can share the actual waveform and photo of board connection offline.

Best Regards,

Satoshi / Japan Disty

  • 0
    TI__Mastermind 30280 points
    Satoshi-san,

    It would be very helpful if you can share the waveform of the issue occurring here in e2e.

    I understand you say the output voltage is oscillating with no load, but what happens when the customer applies a load using the load board?

    The expert on the LP8758-B0 device has been assigned to this question and will respond to you.
  • 0 in reply to Brian Berner
    Guru 21685 points

    Hi Brian,

    I'm sorry but it's difficult to share the customer's waveform on E2E so I'd like to discuss the expert on private message or email.

    Best Regards,

    Satoshi / Japan Disty

  • 0
    TI__Mastermind 42921 points

    Hi Satoshi-san,

      Please follow the guideline below:

    1. Use FB_B0 for Vout+ and FB_B1 (Instead of GND) for Vout- to sense the output as the picture below copied from datasheet.
    2. It's better to limit the lead wires length for the sense lines to 2"; otherwise, use twist wires can help.
    3. Use strong enough lead wires (( IxR drop<2mV even in peak current) for current carrying Vout and GND connection. 
    4. Double check if the EVM configuration resistors J0, J1B, J2B and J3B (as showing by PCB 3D bottom side view below) are soldered properly.

    Thanks!
    Phil

  • 0 in reply to S.Satoshi
    TI__Mastermind 42921 points

    Hi Satoshi-san,

      I also find my attached pictures not showing up properly here. Please share the customer's waveform to my Email: pyi@ti.com; and then I can share you the pictures mentioned in my post message above. 

    Thanks!

    Phil