Hello
I am doing the schematic to generate -5V for a RF amplifier. I have an inverting regulator, ADP5073 that generates the negative supply. Can someone please confirm the noise level as it is not mentioned in the datasheet?
What would be the noise performance if I cascade with a negative LDO such as LT3094?
The noise performance of an LT3094 after a switcher will be similar to what is shown below in the LT3045-1 datasheet page 1 application where the noise out of the LT3045-1 LDO is below the noise floor of the spectrum analyzer. The noise floor of the spectrum analyzer is relatively high in this case because the spectrum analyzer is programmed to have relatively high input attenuation so it can process the switcher noise without overloading, in the scenario where there is no LDO. I would use a ferrite bead-capacitor filter at the output of the switcher to filter the high-frequency switcher noise spikes because LDOs generally cannot reject high frequency noise spikes completely. There are evaluation boards available for both the ADP5073 and LT3094 that you may be able to use to evaluate your system's performance with just the switcher or the switcher plus the LDO. If you use the evaluation boards to power your system, try to use shielded leads like coaxial so the leads don't radiate and make the noise performance look worse than it actually is.
