• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 62 subscribers
  • Views 183 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LP5912: Effect of load side capacitor

Hirotsugu Kobayashi
Mastermind 8745 points
Part Number: LP5912
Other Parts Discussed in Thread: TPS745

Hi team,

2uF is used for the output capacitor of LP5912.
However, 10 ADCs are connected to the load and 10uF is used for the bypass capacitor of each ADC.
The total amount of capacitors on the output side is 102uF.
Is it necessary to keep it within the maximum capacity of 10uF including the bypass capacitor on the load side?

Best Regards,

  • 0
    TI__Genius 12040 points

    Hello,

             Yes, the bypass capacitors would add to the output capacitance of the LDO. It is necessary for the net output capacitance (including the bypass capacitors) to be less than 10uF to ensure stability. Thanks!

    Regards,

    Srikanth

  • 0 in reply to Srikanth Lolla Venkata
    Mastermind 8745 points

    Hi Srikanth,

    The LDO and ADC are quite far apart, but will they affect the stability of the LDO?

  • +1 in reply to Hirotsugu Kobayashi
    TI__Genius 12040 points

    Hello Hirotsugu-San,

                                     There is no simple way to analyze the impact of a long trace on the stability. The most comprehensive method would be to accurately model the impedance of the trace and the 11 capacitors. We would then have to compute the net output impedance, and extract the effective capacitance and ESR from this. If the effective capacitance and ESR fall within the limits provided in Section 7.6 only then can we be confident of stability. As you may agree, this is not straightforward by any means. 

                                      To a first order approximation, it would be best to keep the net capacitance (Output cap plus the bypass caps) within the 10uF limit. As an alternative perhaps you could consider TPS745 which is pin to pin compatible with LP5912 and can support a much larger output capacitor (220uF). Thanks!

    Regards,

    Srikanth