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TPS7A49: Input capacitor

Daniel Gregor
Prodigy 90 points
Part Number: TPS7A49

Hello,

in a special application (current pulse output) I have to reduce the Input capacitor of the TPS7A49 to 47nF to achieve a low rise time (Circuit see attachment).  I have tested the LDO with 47nF without stability problems (5 Boards). To determine the minimum required capacity I have also tested 18pF and also in this case the LDO has been stable. I do not have high requirements regarding the noise. The noise performance with 47nF is sufficient. 

In the datasheet min 10µF are recommended. Can I also use 47nF when I sufficient with the noise? The important thing is that we don’t not have stability problems in mass productions. 

Thanks!

Daniel

SKMBT_28317031520100.pdf

  • 0
    TI__Guru 55940 points
    Hi Daniel,

    Per the capacitor requirements section of the datasheet we actually require a minimum input capacitor of 2.2uF as this is where we designed, characterized, and tested this device to operate. We recommend 10uF in order to maximize ac performance. That being said a smaller input capacitor may satisfy your specific application since the input capacitor requirement is somewhat dependent on your upstream source. The way to determine this is to do prototype testing as you have done with 5 boards. During this testing you should subject the LDO to your worst case conditions (transients, temperature, etc).

    Very Respectfully,
    Ryan