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some examples for practical LATCH UP?????

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mahendra

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Hi all

I want to find practical situations of latch up when an IC powered with clean power supply.Plz help in this regard.Thnx in advance.
 

steer

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One example of latchup is if one leaves Nwell floating.
Another example is if one has a small number of substrate or Nwell contacts, a fast switching large transistor can change local substrate of Nwell potential by capacitive coupling. That can trigger latchup in proper curcumstances.
Both scenerious can happen with perfectly clean supplies.
 

mahendra

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HI
Thanx for the reply.

if low frequency circuit then how it reacts for the latch-up???

Let us discuss with one example,Low frequency OP-AMP.ALL SUBSTRATE CONTACTS ARE CONNECTED TO THE POWER RAILS. What r causes of latch-up in this case??
 

steer

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If circuit is slow, all supplies are ideal and Nwell and Pwell are connected to supply and gnd rails, then no latchup is possible.

BUT, is power-up and power-down of your circuit slow enough?
Can nearby digital circuit inject minority carriers into the common substrate that diffuse to your slow op-amp and fire latchup then?
Is input of your op-amp is clean of high-frequency components? Can output be overdriven?
All these reasons can lead to the latchup, albeit much less probable for a slow circuit.
 

    mahendra

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mahendra

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Thts good.


Thanx a lot.I could get some conclusions.

Regards
Mahendra
 

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