Dear All
I need your help to understand about latch up test set up. I do not know if we need to connect the any capacitor between Vcc to GND. This is a problem as the result is different for case with and without capacitor (pass & fail latch up). Any idea? Thank you to enlighten
best rgds Jason
--
Yes.
I dT
dV = ------
C
what happens to dV as as C goes to zero?
You don't write what kind of stimulus you provide, but when a steep pulse is applied to an input and the internal protection diodes conduct the input current onto the rails, you might have a voltage transient which exceeds the max. ratings at the supply terminals. That is not latch-up, but overvoltage breakdown. Talk to the guy who designed this test rig, and put a transil across the rails as close to the device as possible.
-- ciao Ban Apricale, Italy
Dear John
The V for sure will goes to infinity if C tends to go 0. C is 0 giving very high impedance between Vcc and gnd if the capacitance is between the mentioned 2 nodes. How should I interprete this? Kindly enlighten
Dear Ban
Grazie for the help. The test is by positive and negative injection of high current separately to the pad. Are all device come with dioe protection which you mentioned? Kindly enlighten as well
best rgds Jason
------------------------------------------------------------------------------- Ban wrote:
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DNA
In terms of dumb f*ck things to do that was a pretty dumb f*ck thing to do. Even I have not been dumb f*ck enough to use the access provided by a company I have worked for to ask a dumb f*ck question on usenet.
Either the company you are working for has an attitude that makes you afraid to ask them questions or you have the attitude. I'd vote for the former. Either way someone needs to get rid of it.
DNA
Yes, all opamps have protection diodes either between the inputs and/or to the supply rails. You *have to* monitor directly the voltage across the supply pins and make sure that your injected current is shunted to gnd without rising the rail voltage. Generally this might happen if the injected current is higher than the idle supply current of the opamp. You also have to observe the max. input current rating provided in the datasheet. A cap helps with short pulses and the zener or transil will do it for DC. These intrinsically have quite a capacitance and are fast, making a cap unnecessary in this case, but I would do both.
-- ciao Ban Apricale, Italy
Hello Ban
Thanks a lot for the wonderful lesson. By the way, if you know of any document online which touch about the observation of injection current to diode and the rails and their mechanism in details, kindly let me know the link. Please let me know if I can email to your mailbox.
Thank you Ban
yours Jas> jas> > Dear John
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