LP5910: LP5910 LDO PSRR measurement

Hi Roy,

Here are some app notes which discuss measuring PSRR in general.

https://www.ti.com/lit/an/slaa414a/slaa414a.pdf

https://www.ti.com/lit/an/slyt547/slyt547.pdf

https://www.omicron-lab.com/fileadmin/assets/Bode_100/ApplicationNotes/PSRR/App_Note_PSRR_2_0.pdf

When I measure PSRR I use the Omicron Bode 100 with the Line Injector module from Picotest.  This assumes that the LDO does not require an input capacitor.  If the LDO requires an input capacitor then you need a different method such as what is used in the first app note I provided, as the Bode 100 + line injector are not capable of driving the capacitor at high frequencies while maintaining the injection level.

Thanks,

- Stephen

Hi Roy,

The simulation looks correct to me.  Here are the results.  The TI legacy simulation models are accurate with regards to the typical DC attenuation, the first pole and the first zero.  You can see that they used about -80 dB as the DC attenuation, followed by a pole at around 1 kHz and a zero around 200 kHz.  This approximates what you see in the datasheet in figures 11, 12 and 13.

Thanks,

- Stephen