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LME49600: PSRR

Part Number: LME49600

Hello,

When look at datasheet page7, there are PSRR characteristics data.

Figure 18 and 20 are same title +PSRR vs Frequency VS = ±15V, Wide BW Mode.

What is different? Could Figure 20 be -PSRR?

Also, are Figure 19 and 21 same story?

 

Regards,

Mochizuki

  • Hello Mochizuki-san,

    Thank you for bringing these PSRR graphs to our attention.  This part is an older National Semiconductor part.  There appears to be a labelling error; please utilize my mappings below:

    Figure 18: -PSRR vs Frequency; Vs = +/- 15V, Low Iq Mode

    Figure 19: Correctly labelled

    Figure 20: -PSRR vs Frequency, Vs = +/- 15V, Wide BW Mode

    Figure 21: +PSRR vs. Frequency, Vs = +/- 15V, Wide BW Mode

    The Low Iq Mode curves are very similar, if not identical, for the LME49600.

    Best,

    Alec

  • Hi Alec,

    Thank you for your prompt information.

    Now our customer is struggling to reject -Vss power supply ripple noise at 100Hz or 120Hz.

    It seems - PSRR is -5dB lower than +PSRR by fundamental design, do you have a suggestion to improve -PSRR characteristics on EE application?

    Is there any cross-selling substitutable BUF device?

    Regards,

    Mochizuki

  • Hi Mochizuki-san, 

    Alec is out of the office today, so I will provide some comment. The part should maintain ~-70dB PSRR at 100-120Hz, which is going to be similar to what I would expect from other buffers. Would it be possible to add some additional power supply decoupling to the device, particularly with capacitors targeted to that frequency range. 

    Regards, 

    Jacob 

  • Hello Mochizuki-san,

    Were you able to consider adding additional power supply decoupling capacitors to the device, with the targeted frequency range suggested above?  Please let me know if you need further assistance.

    Best,

    Alec