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LP2981: P2P Compatible, Drop in Replacement

JP
Expert 3801 points
Part Number: LP2981
Other Parts Discussed in Thread: LP2985, LP2992

Hello Team,

I am currently looking for a P2P compatible solution for the LP2981 in 5-Pin SOT-23 Package. The general requirements are:

  • Vin (max) must be 8V or more
  • Iout is 150mA (max)
  • Output is fixed, but ADJ works as well

So far I am considering using the TPS709xx devices as this meets all the requiremetns, but I was also interested in the LP2992, and LP2985. Both the LP2992 and LP2985, have a bypass cap pin which is a "NC" on the LP2981. 

This leads to my question, as to whether or not the bypass cap is required for those devices? In the datasheet it is assumed that the bypass cap will be used, but for cases of replacing the LP2981 on an existing board, we cannot add a cap. 

Thank you for your help in advance, and if there is a better solution that I may have overlooked please let me know!

Best Regards,

Javier Palomo

  • 0
    TI__Guru 55940 points
    Hi Javier,

    The bypass capacitor serves the same function as a noise reduction capacitor on other LDOs. This capacitor is not required for stability (several of the typical characteristics curves in both datasheets show Cbypass as open); however, noise performance and ac performance such as PSRR and transient response will not be optimized without the capacitor.

    Very Respectfully,
    Ryan