why 200 ohm is used in ESD protection circuits?

[lhlbluesky]

why 200 ohm?

in ESD protect circuit,why 200 ohm resistor is used?i mean,why is it not any other value,such as 1K,10 ohm etc.is there any reasons?

 

[vomit]

Re: why 200 ohm?

There is no rule to use 200 ohm. Your circuit has it, but it may be any other value.
It's a tradeoff between the advantages of
- a high resistance (force a very low current in case a ESD voltage spike enters)
- a low resistance (not too much voltage drop during its normal use)

In your case the designer made the tradeoff at 200 ohms for that particular circuit usage.

 

[ESDSolutions]

Re: why 200 ohm?

Vomit is right regarding the trade-off. Higher resistance can increase ESD robustness... BUT be sure to provide primary protection path for the ESD current. A resistor alone will not protect against ESD! A large resistor will ensure that ESD current searches for shunt paths with lower impedance.

Many leading foundries ask for a 200 ohm resistor between the bondpad and the sensitive (IO) circuits. Maybe this is where this value is coming from?

However high resistance at the pad reduces functional performance: speed and output voltage are reduced.

 

[andyjackcao]

Re: why 200 ohm?

I would like to add something;

except what's said above, I think that the protection for CDM is need to be

considerated;if the resistor is too huge, then the second protectin for CDM will be

damaged

 

[zjrlgf]

Re: why 200 ohm?

thanks, learns a lot