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[AmpeRose] And yet another problem… Experts… A word…

Hello,

So, in previous posts, we’ve shown you the results of simulating Switches, initial calibration, automatic calibration sub-system, etc. In addition, we’ve talked about some problems and how we’ve approached them and shared the results with you. However, we are still having a little problem, let’s see what’s happening… The origin of the problem is the DUT itself, to be more precise, it’s the decoupling capacitors that are bothering us. Yesterday, we showed you (In this post) that  a decoupling capacitor must be used by the DUT to ensure that we do not have a big voltage drop in case of a very fast transition between current ranges. This guarantees that the DUT will always be powered up.

Now, we’re getting closer to the problem.

Problem Statement

A negative current is being fed to AmpeRose by the decoupling capacitors during fast current transitions, therefore delaying the stabilisation of the op amp output.

Remember that we’re sampling each 10 us. That being said, a lot of samples would need to be discarded (~ 70) before voltage stabilization.

What do we want?

We want to block the current flowing from the decoupling capacitor of the DUT, easy, let’s use a diode.

Not that easy! In fact, an ideal diode would have definitely solved our problem(?), because it allows the current to flow in one direction only and does not consume any voltage (drop voltage = 0). However, such a diode does not exist… 🙁

Different solutions

Constructors (Linear tech, Maxim,…) provide different near-ideal diode solutions. However, the drop voltage is still huge, and therefore not suitable for our needs.

Well, I hope I made the problem clear… If you have any questions or clarification requests, we’re here to answer… And, it goes without saying… We’re open for any and all suggestions.

Thank you.

Bilal ADDAM

2 comments to [AmpeRose] And yet another problem… Experts… A word…

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