5V PIC noise tolerance

Hi All:

I have a project running a capacitive discharge off a 36V supply. The 36V is also regulated via an LM317 to 12V and then via another to 5.12V.
The discharges are causing some 500Hz sub 150mV ac spikes (5uSec kickback) on the 5.12 Vreg line meant to feed a 16F886 and 16x2LCD.

Now the 16F886 knows when the pulses take place so it can avoid using the adc when the transient is happening as the Vref = 5.12 Vcc.

What I am wondering is if the PIC is tolerant (no resets) of 0.15V spikes on its Vcc?
Or do I need to make an independent supply for it?

I would have though 0.15V spikes are no concern at all - however, I would also suggest that it 'might' not even have such spikes - often a scope will pick up such spikes directly, and not give an accurate representation of the supply lines.

I'm presuming you have suitable decoupling capacitors close to both the PIC and LCD, plus sensible layout.

hello am looking on how to have a circuit that takes in 0-6 vollt and 5-0 volt output.though am new to electronics am i can assemble a circuit.

Nigel Goodwin said:

I would have though 0.15V spikes are no concern at all - however, I would also suggest that it 'might' not even have such spikes - often a scope will pick up such spikes directly, and not give an accurate representation of the supply lines.

I'm presuming you have suitable decoupling capacitors close to both the PIC and LCD, plus sensible layout.

Click to expand...

That's quite possible, as the scope shows different amplitudes depending on the angle of the probe, so the <.15V is the smallest I could get . I am still using the 3" ground clip which does pick up extra noise. I know there's some as a ferrite bead reduces it a bit. I have some low frequency (10Mhz) beads on order as their is a bit of 25Mhz, 100mV ringing on the transition edges.