PSRR improvement in BGR ckt

[Safiya]

hi,
My variation in bgr is 187uV with temp from -30 to 80C . is it acceptable? output is stable through out in transient and dc-response.
and my PSRR is -53dB. is the PSRR is enough or have to improve further , and how to improve ?
Thanks
Safiya

 

[yuvan]

That depends on your requirement, but can you post the circuit and input /output levels?

 

[dick_freebird]

First off, consider the problem of dynamic vs static PSRR.
Your bandgap is fed by something. Do you care if that
something's incoming ripple is passed unattenuated to
the destination?

For DC PSRR, 53dB is OK for DC accuracy goals on
a power management device; not OK for a data acq
reference beyond about 8-10 bits.

For RF applications you see people advertising 40dB
at 1MHz PSRRs, so the upstream switcher's ripple is
well-killed. That means a much higher DC PSRR.

The single easiest thing is to power the bandgap
from a local "poor boy" LDO regulator that has some
really good HF PSRR, maybe not fabulous (or even
regulated) DC accuracy. Like a low-VT NMOS
follower biased by a resistor/MOS diode stack and
decouple the heck out of its gate and source.
This makes vdd' a cleaner (AC-wise) power supply
and adds directly to your PSRR without messing the
bandgap itself around, any.