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newic

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ESD protection for multi-supply
Mar 18^th, 2015, 11:38pm

Hi

How is the ESD protection scheme for multi-supply system? I am more concerns on ESD event from VDD1 to VDD2, assume VDD2 is a reference during ESD event.
I read some books that recommends to add bidirectional diode between 2 supplies. But it will cause leakage during power up event. is it a practical solution?
Is there any good solution?

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newic Senior Member Offline Posts: 138	Re: ESD protection for multi-supply Reply #1 - Apr 14^th, 2015, 7:41pm any expert can comment??
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RobG Community Fellow Offline Posts: 570 Bozeman, MT	Re: ESD protection for multi-supply Reply #2 - Apr 15^th, 2015, 2:49am I'm not even close to an expert, but the Vdd pads I see these days have a snapback device between the pad and ground. This protects each Vdd pad relative to ground so there is no need to put diodes between the separate Vdds.
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newic Senior Member Offline Posts: 138	Re: ESD protection for multi-supply Reply #3 - Apr 16^th, 2015, 12:54am hi It is true that each supplies has a clamp between vdd1/2 to vss. But the clamp will not turn on if Vdd1 & Vdd2 did not have a common ground. The charge can go from vdd1 to vdd2 through the level shifter circuit instead of going through vss. assume Vdd1 pairs with vss1 while vdd2 pairs with vss2.
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RobG Community Fellow Offline Posts: 570 Bozeman, MT	Re: ESD protection for multi-supply Reply #4 - Apr 16^th, 2015, 1:53am I guess you would have your snapbacks between the vdd pads and a common line, such as substrate or one of the vss lines. Then put back-to-back diodes between the vss pads.
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newic Senior Member Offline Posts: 138	Re: ESD protection for multi-supply Reply #5 - Apr 16^th, 2015, 10:13pm Hi RobG, it is not a snapback ESD device at the power supplies. CMOS RC-Triggered MOSFET ESD Power Clamp is used instead. Is there a problem?
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RobG Community Fellow Offline Posts: 570 Bozeman, MT	Re: ESD protection for multi-supply Reply #6 - Apr 17^th, 2015, 7:08am Yes, same idea. I see my Vdd pads use the RC clamps.
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newic Senior Member Offline Posts: 138	Re: ESD protection for multi-supply Reply #7 - Apr 22^nd, 2015, 1:13am thx!!
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