TPS7A89: charge pump noise

Hi Mark,

Please find the charge pump noise vs frequency below.  Please keep in mind that a pi-filter can be used to filter out the charge pump noise.

Very Respectfully,

Ryan

Dear Ryan:

Please explain how I calculate the peak-to-peak charge pump noise from the noise density plot?

Can you provide an oscilloscope image of the charge pump noise?

Regards,

Mark

Hi Mark,

The noise spectral density must first be converted to RMS. Our RMS measurement for the bandwidth is 4.5 uVrms per the legend of the graph. From the RMS voltage can be converted to peak to peak by simply multiplying by 6. We multiply by 6 because the RMS voltage represents one standard deviation of the noise. To estimate the peak to peak using +/- 3 standard deviations we must multiple by 6. This yields 27 uVpp.

Very Respectfully,
Ryan