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Design >> Analog Design >> double guard-ring in driver & pre-driver
https://designers-guide.org/forum/YaBB.pl?num=1319089745

Message started by newic on Oct 19^th, 2011, 10:49pm

Title: double guard-ring in driver & pre-driver
Post by newic on Oct 19^th, 2011, 10:49pm

normally double guard-ring is added in the IO driver which has large current. How about pre-driver? Should guard-ring be added into the pre-driver. Predriver consume average current about 1.5mA.

Title: Re: double guard-ring in driver & pre-driver
Post by raja.cedt on Oct 20^th, 2011, 12:25am

what do you mean by double ring driver? is it h-bridge driver?

Title: Re: double guard-ring in driver & pre-driver
Post by newic on Oct 20^th, 2011, 12:49am

inverter based voltage driver which is very noisy as compared to current driver.

double guard-ring is added to protect latch up issue

Title: Re: double guard-ring in driver & pre-driver
Post by raja.cedt on Oct 20^th, 2011, 12:54am

so double gaurd is layout rite, so no need to care from ckt point of view? So your's is voltage mode driver, so pre-drivers also kind of inverter based sturctre. To be frank i didn't understand the question. Because you are telling pre-driver consumes 1.5ma, and again you are asking wht about pre-driver...!!

Thanks,
Raj.

Title: Re: double guard-ring in driver & pre-driver
Post by newic on Oct 20^th, 2011, 1:04am

question: "Should guard-ring be added into the pre-driver." which this pre-drive consume about 1.5mA

Title: Re: double guard-ring in driver & pre-driver
Post by loose-electron on Oct 21^st, 2011, 5:58am

explicitly define your circuit
explicitly define what the circuit is supposed to do
explicitly define your layout
explicitly define your voltages, currents frequency
ask the question

without the above information its
impossible to answer the question

Title: Re: double guard-ring in driver & pre-driver
Post by vp1953 on Oct 22^nd, 2011, 9:54am

Hi Newic,

It probably does not hurt to have a double guard ring around the pre-driver. Aside from latch up prevention, it also helps to keep substrate currents confined to the local area, a factor that is of importance if the IO driver is sourcing large currents. 1.5mA does not seem like a huge current but if there are VCO's, bias generators etc in close proximity, having a double guard ring around the predriver would be helpful.

Title: Re: double guard-ring in driver & pre-driver
Post by chaojixin on Nov 6^th, 2011, 6:25pm

newic wrote on Oct 20^th, 2011, 12:49am:

inverter based voltage driver which is very noisy as compared to current driver.

double guard-ring is added to protect latch up issue

Hi, may I ask how to determine the width of guard-ring to prevent the latch-up? how to do the calculation, and what tools is needed?

thanks!

Title: Re: double guard-ring in driver & pre-driver
Post by loose-electron on Nov 7^th, 2011, 1:08pm

foundry will have physical design rules for latch-up

These are minimum.

Suggest that substrate grounds and N-well rings be connected back to metal ground-power bias connection as much as possible.

Title: Re: double guard-ring in driver & pre-driver
Post by chaojixin on Nov 9^th, 2011, 4:55pm

thank you very much!