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LP2951-Q1: What is max (VO-VIN)?

Basil
Intellectual 1620 points
Part Number: LP2951-Q1

Dear Team,

I'm using the LP2951-Q1 in a design where's there is a risk of VOUT going above VIN.

What is the maximum (VOUT-VIN) that the device can handle without any external protection?

Thanks and best regards,

B

  • 0
    TI__Expert 7015 points
    Hi Basil,

    The device can only handle Vin + 0.3V at the output. It should be limited to less than this to avoid damage to the device.

    Regards,
    Mark
  • 0 in reply to Mark Sellers
    TI__Intellectual 1620 points
    Hi Mark,

    thanks a lot for your quick reply and for your support.

    I've got one more question:
    when using the 5V fixed output, do we need C_Bypass?
    If yes, what is the formula to calculate its value?

    Thanks and best regards,
    B
  • 0 in reply to Basil
    TI__Expert 7015 points
    Hi Basil,

    You do not need the C_Bypass cap (feed forward) for this LDO to operate correctly. However, you may want to use the bypass capacitor to get the better noise and transient performance that it can provide. Without knowing the exact values of the internal feedback resistors it is hard to say how to calculate the effect of the C_bypass capacitor. But typically the values for these capacitors would be from 100pF to 10nF. If you use capacitors in that range you should be fine.

    One thing to watch out for with this LDO is that if you use ceramic caps you may need to add extra ESR to get the part to be stable. If you plan to use ceramics I would check the datasheet and see what the ESR is and make sure that it falls within the recommended range of this LDO. If it doesn't you will have to add ESR to the capacitor.

    Also, here is an app note on feed forward capacitors that should help quantify their benefits some more:
    www.ti.com/.../sbva042.pdf

    Best Regards,
    Mark
  • 0 in reply to Mark Sellers
    TI__Intellectual 1620 points
    Hi Mark,

    great help, thanks a lot!

    Regards,
    B