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LP2985: LP2985-333DBVR

Rock Shao
Expert 2995 points
Part Number: LP2985

Hi Team,

U5 position is to use TI LP2985-333DBVR for this part.
The output capacitor originally had C25, C1, and C2, but we now replace C25 with 1KΩ,
Only C1 and C2 are relatively close to U1 (MCU). How about this for TI’s IC?
Are there any influences? Thanks.

  • 0
    TI__Intellectual 2250 points

    Hey Rock,

    Thanks a lot for reaching out.

    I have few questions regarding the changes. Please provide me the details so that I can provide details on this:

    • Instead of C25, now a 1K resistance is placed between LDO output and Ground. Please correct me on this.
    • As you mentioned about C1 and C2 being far from LDO and closure to MCU. Can you get some info on parasitic parameters (such as resistance, inductance etc). Any resistance on this path will act as ESR for the LDO loop stability. Similarly any parasitic inductance can act as ESL and show huge ringing in terms of load transients. This can directly impact the stability of the LDO loop.

    Regards,
    Rohit

  • 0 in reply to Rohit Phogat1
    Expert 2995 points

    Hi Rohit,

    Thanks for your reply quickly.

    Yes, the customer replaced the C25 4.7uF to 1K. Are there any influences? Thanks.

  • 0 in reply to Rock Shao
    TI__Intellectual 2250 points

    Hey Rock,

    My apologies for delayed response on this.
    No I don't see any issue with this. I was interested to see that customer deliberately flowing 3.3mA current from the LDO to ground. Is this for specific application. Just to update you, LP2985-33DBVR is stable with 0mA current also. 

    Regards,

    Rohit Phogat