ADP323 Pulsing Spikes

Can Anyone please answer the previous question, if can be done...

Thanks.

There may be a couple issues here.

I assume the EN1 signal has very fast rise and fall times.  This could be injecting noise into the ground and causing the noise to appear.  It may be common mode signal since you are seeing on GND.

Can you put a scope probe on GND and short the probe ground connection to the scope input when measuring the noise on the GND?  If you still see the spikes, it is definitely common mode noise, not differential mode noise.  This isn't really an issue unless your circuit has poor common mode rejection.  Slowing the EN1 pulse edges with an RC should help.  Try to limit the rise and fall times to a few microseconds or longer.

I noticed that the output voltage divider resistances are very high.  Is it possible to reduce them by a factor of 10?  This also might help reduce the coupling of the EN1 signal into the output.

Do you have a load on the output of Vout1. If you load is demanding a lot of current then you may be forcing a transient at the input of the LDO. You may need additional input capacitance.

Also since the output cap is being charged when you disable it, the input cap is sourcing current to recharge it when you re-enable the LDO, again higher input cap may be needed in this case.

LucaV