Hi team,
We used to use LP38798 to power PLL device in radio system. And now we want to use TPS7A92 to replace it. How could i judge which device performance is better? From noise density aspect, both device is ~5uVrms, but the PSRR performance have a large difference.
The user case is that:
Vin:3.68V, Vout=3.3V, Io=600mA. Vin is coming from DCDC, which fs=700kHz~1MHz.
Thanks in advance
B.R.
Lucas
Hi Lucas,
The TPS7A92 will perform similarly however at those frequencies the LP38798 will filter out more of the ripple coming from the DCDC. So it depends on what the peak to peak ripple is and how much attenuation the load requires.
Looking at similar load currents you can use the two graphs below to get a very good idea of the difference in PSRR between that the two devices will have. This is because they use the same headroom (Vin-Vout=500mV), note that the output voltage does not change the PSRR much.
TPS7A92
LP38798
