How to improve low frequency PSRR of bandgap reference circuit in PCB

[bhl777]

Hi all, I have a bandgap reference circuit on PCB board. Internal circuits cannot be changed, but external components can be freely chosen.
The measured low frequency(up to 1kHz) PSRR is around -15dB but simulation results showed around -50dB. I am not sure if any external circuits can help about this. Can anyone advise?
I did look into this thread, https://www.edaboard.com/threads/52940/, but it seems it deals with high frequency PSRR. In my case, low frequency PSRR is more important, and do I need to do something in power supply to improve it?
Thank you!

 

[Dominik Przyborowski]

Do You include in your simulations bonds and pcb paths inductance? After full chip RC extraction the PSRR is also quite good?

 

[bhl777]

Do You include in your simulations bonds and pcb paths inductance? After full chip RC extraction the PSRR is also quite good?

Hi Dominik, I did not include bondpads and pcb paths inductance in simulation. If they are the problems causing bad low frequency PSRR, how can I improve it on board? Thank you!

 

[crutschow]

Post your schematic and simulation.

 

[bhl777]

Post your schematic and simulation.

That is traditional first order bandgap, with opamp and cascode current mirrors to generate PTAT current. Simulation with the schematic (not post-process simulation) is like this


The measurement setup is similar to what used to be done for power supply audio susceptibility, like this


Thank you!