SPIKE FILTER CIRCUIT FOR CMOS IC

[Ajay Jamdar]

Hi,
I am facing problem always while i am making any circuit related to CMOS-IC 4000 series,that if i switch ON/OFF mains power supply 230VAC suddenly IC tooks spike & gives result that should come by any logic means example : Alarm gets ON,relay operated by IC gets ON etc.

I am looking for interface OR filter circuit which i can built at input pins of IC OR filter circuit which will avoid this malfunctioning of IC caused by spike /frequent ON-OFF in power.

Please suggest.

Ajay J.

[pebe]

I assume you already have smoothing caps on your supply rails. You can provide an effective cure in most cases by putting simple low-pass filters on input pins. Take the feed to the input pin via a 10K resistor fitted as close to the pin as possible, and fit a 1nF cap between input pin and ground. Also, the physical layout of components can sometimes cause such problems by creating ground loops that give unwanted coupling.

It is difficult to be more specific without seeing the circuit - If you care to provide one we can probably give you a more comprehensive reply.

[dave0885]

you could try and put a zenner diode across the + and - teminals something like a BZY55- x, x being the suply voltage IE if its a 12v circuit use a BZY55/12, this will stop the spike voltage as ive used this array in many automotive cicuits ive built and it works every time