AllenNeuralDynamics / harp.device.lickety-split

an ephys-compliant capacitive lick detector
MIT License
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V0.7: Analog switches cannot represent negative voltages #37

Open Poofjunior opened 4 months ago

Poofjunior commented 4 months ago

The original analog switch TS5A9411DCKR (datasheet) cannot represent negative voltages. There are two possible fixes for this:

I've opted for the second option although neither of the above two are obvious solutions here and require some testing.

The datasheet specifies that it operates on as low as +/-1.8V, but it also specifies that digital control inputs should be less than V+ + 0.3V, and that we should limit the current if they must operate in that condition. It also doesn't specify VIH in a number of cases that it should work in, including our +/-2.5V range. I have tested on the bench that VIH can be as low as 1.5V in a +/-2.5V supply configuration, so this part should be able to be substituted in with the necessary PCB changes.