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Design >> Analog Design >> 3.3V vs 14V
https://designers-guide.org/forum/YaBB.pl?num=1353449147

Message started by grosser on Nov 20^th, 2012, 2:05pm

Title: 3.3V vs 14V
Post by grosser on Nov 20^th, 2012, 2:05pm

hello

will it be safe to use 3.3V transistors with 4.2V supply ? Gate oxide breakdown, diode junction breakdown is 7V and punch through voltage is 6.6V. It is 0.35um process
Or I should use hv transistors ready for 14V?

regards
grosser

Title: Re: 3.3V vs 14V
Post by boe on Nov 20^th, 2012, 2:55pm

Grosser,

this is determined by the reliability of the transistor wrt. hot-electron injection. It does not depend on breakdown or punch-through voltage.

You need reliability data from your fab to answer that; the issue will be most critical for minimum-length transistors

- B O E

Title: Re: 3.3V vs 14V
Post by analog_wiz on Nov 20^th, 2012, 7:05pm

Hi Grosser, it would depend on the topology you are using.What you can

do it run a transient simulation and measure the voltage across the transistor junctions(eldo has something called reliability simulations...). You could also use ultrasim and it has reliability checks for checking voltages across various junctions and it can flag violations if any when a transient sim is run.

Title: Re: 3.3V vs 14V
Post by carlgrace on Nov 21^st, 2012, 9:21am

The voltage requirements are based on differences between terminals (except for things like well breakdown).

If you don't ever have the 4.2 V across a gate-source or drain-source junction you're golden. Be sure you carefully check the startup sequence and ESD structures on your chip though... you may need a custom pad (depends on your pad library of course)

Title: Re: 3.3V vs 14V
Post by Lex on Nov 22^nd, 2012, 7:57am

carlgrace wrote on Nov 21^st, 2012, 9:21am:

I would think that VGS and VGD should not exceed 3.3V, and expect that VDS can handle higher voltages.