Hello Ti-Experts,
I built a simple buffer circuit using the TPS60403 for biasing with the 3 recommended 1uF capacitors from the datasheet.
My load current idles at about 40 uA and swings around that q-point within 55uA 25uA.
The TPS60403 voltage inverter is connected in such way, that this load current flows between Pin 1 (Out) and Pin 4 (GND).
Of course the ripple which the charge pump creates should be minimized. I used the ripple-formula for V_O(ripple) given in the datasheet prior to buying the part, which gave a negligible ripple of 2mV for this load current I_O. Right now the noise created by the charge pump is more in the area of 40 mV (peak-to-peak) which is too high.
In the datasheet table 4. shows results using a LC-Post Filter at the output of the TPS60400, and also a higher output capacitance C_O.
The lowest ripple and noise is achieved there by using a C_O of 10uF plus the LC-Post Filter.
Before trying out different values and filters, can you tell me whether I should use a different part for this application or need to stabilize the -5V from the charge pump e.g. with an LDO?
Or can I resolve the noise issue by using the LC filter configuration without influencing the dynamic behaviour of the whole circuit at this low current?
I Appreciate any support,
Thank you
