• State TI Thinks Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 295 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

TPS7H1101A-SP: For Low noise applications - input/output cap sizing

Susan Miracle
Prodigy 70 points
Part Number: TPS7H1101A-SP
Other Parts Discussed in Thread: TPS7H1111-SP

Hi,

I have a low noise application.  When I look at the noise figures in the data sheet, they reference input/output capacitance of 220uF for each.  How dependent is low noise on input/output capacitance sizing?  To get the results below do I need 220uF for input/output capacitance?  Or can I get by with less input capacitance, because what really matters is the output capacitance?  This is being sourced by an upstream converter, which has at least 300uF of output capacitance.  If the output of the converter feeding this LDO is close in terms of layout, perhaps, I don't need a lot of input capacitance?  Thanks!

  • 0
    TI__Guru 62930 points

    Susan,

    There are various aspects that would impact the noise spectral density on the output of the LDO.  Much of this is internal to the design and noise on the internally generated reference voltage.

    The capacitance on the soft start pin will likely influence the noise on the TPS7H1101A, as it is associated with the reference voltage.  I do not have characterization data on the influence of CSS on this LDO.

    If you are in need of a low noise, high PSRR LDO, you might be able to take advantage of our new space rated RHA LDO that is currently available as pre-production with an expected fully qualified production availability in the June timeframe. 

    The TPS7H1111-SP currently has EVMs, and EM units available.

    See: https://www.ti.com/product/TPS7H1111-SP

    And for EVM : https://www.ti.com/tool/TPS7H1111EVM-CVAL

    If you are locked into the TPS7H1101A, I can take a look at evaluating noise performance with respect to Css.   I can also look at your exact Vin/Vout load conditions. 

    Regards,

    Wade

  • 0 in reply to Wade Vonbergen
    TI__Guru 62930 points

    I did get some feedback indicating that this LDO does not use the CSS to filter the bandgap.  Thus increased Css will not substantially impact noise performance.

    If you need further assistance, please reply back.