[SOLVED] what diode should I use to protection my circuit Max input 6.5v?

[sheng]

Hi,

I am designing a circuit that allow max of 6.5v. Any suggestion on the diode for protection? For instance if someone hook up a 9V to the circuit nothing will happen to the circuit and will run fine next time.

Thanks.

 

[ashugtiwari]

Use the switching regulator or dc-dc charge pump convertor like MCP1252 etc. You can also use linear drop out regulator like LM series. zener diode will work too but heat dissipation will rise. But, if you are worried about the transient and spike protection, simply use metal oxide varistor or diode bypass circuit to power lines.

Hope that helps.

 

[zzllearner]

would you mind describe the diode bypass circuit in detail?
Thank you in advance!

 

[ashugtiwari]

This is diode protection for any surges. The capacitor help acts as surge filter and send the surge signal to chassis. The diode to Vcc will send positive surge to Vcc and is filtered by bypass caps in Vcc to chassis ground. The diode to ground sends the negative surge to chassis ground directly. Sorry for little bad explanation. actually, in a little hurry

Hope that helps.

 

[sheng]

Thanks guys for the answer, LM ldo maybe the way to go for my design.

 

[zzllearner]

Thank you for your particular explanation, you have helped me a lot.

 

[ashugtiwari]

Since, I was in hurry, i wanted to tell, you can also add a high wattage resistor between Capacitor and I/O1 i.e. at the input. This helps to reduce the surge energy much more bu converting it to heat and this is optional.
In one of my old designs, i have uased 1W to 2W SMD resistor along with above circuit and it helped me to few 100V surge protection (both in with and without resistor), usually something700 to 800V.

 

[zzllearner]

Thank you for your generosity.

 

[sheng]

Thank you ashugtiwari, great information.