ESD question about protection circuit at the output

[ccw27]

ESD Question

Suppose I have an output buffer which will connect to output pad and for MOS layout I comply with ESD rule. Do I still need to add I/O ESD protection circuit at the output?

Thanks

 

[DoctorProf]

Re: ESD Question

The need for extra protection really depends on the process. Some of the processes I work with have very fragle NMOS transistors (drain silicide shorts to body) others are more robust. If the output transistor is large enough and is designed with the same rules as the ESD device then it could be OK. You really need to discuss this with the foundry.

Adding specific ESD clamping/stearing elements is always a safer bet. The ones that provide the best protection are the ones that trigger (start to conduct) prior to the output device and have a low enough resistance that the voltage does not exceed the breakdown of the output device. The ESD clamping device should be tied to the same local power bus as the output device.

DrProf

 

[obi1]

ESD Question

depends of how powerfull is the output driver and the enviroment conditions

 

[phoebe]

ESD Question

if your output buffer strong and close to the pad enough, then needn't I/O ESD protection

 

[laglead]

Re: ESD Question

Generally, making output driver meet ESD requirement is enough.

 

[laydesign]

Re: ESD Question

Suppose I have an output buffer which will connect to output pad and for MOS layout I comply with ESD rule. Do I still need to add I/O ESD protection circuit at the output?

Thanks

The output MOS width + the ESD MOS width fit the ESD current discharge ability .
If the Output mos width is big enough , You don't need esd . If the output mos width is not big enough , add the following mos width with the extra ESD structure .

best regard!

 

[srivatsan]

ESD Question

I dont agree at all with not having the ESD protection because presence of "good" output buffer is at best secondary protection inspite of following all ESD rules.

Anyways, if you do follow the ESD rules, have you seen its frequency response in the desired range for the application?

Srivats

 

[analog99]

Re: ESD Question

Would like to suggest always adding ESD circuits whenever possible unless your output device is huge

 

[williamy]

ESD Question

generally, the output stage dose not need I/O ESD protection. If you add protection, you must take care that the out performance is not affected by ESD protection circuits.