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grosser Community Member Offline Posts: 57	3.3V vs 14V 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
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boe Community Fellow Offline Posts: 615	Re: 3.3V vs 14V Reply #1 - 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
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analog_wiz

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Universe

Re: 3.3V vs 14V
Reply #2 - 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.

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carlgrace

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Berkeley, CA

Re: 3.3V vs 14V
Reply #3 - 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)

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Lex

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Eindhoven, Holland

Re: 3.3V vs 14V
Reply #4 - Nov 22^nd, 2012, 7:57am

carlgrace wrote 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. �...

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

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