HCT4051 leakage

Hi,

Has anybody measured typical leakage currents for an HCT4051 analog
mux? I'm wondering about both ESD diode leakage (ie, to rails) and
leakage through open switches. I'm running 0 and +5V rails.

Indications are that everybody's 0.1 uA max spec is wildly
pessimistic, but I was wondering if anybody knows more, before I have
to drag my *** into the lab and make actual measurements. It's a lot
easier to sit here and type and eat bon-bons.

We're scanning eight RTDs. A +2.5 volt reference goes through a
precision 270 ohm resistor and gets mux'd to a selected RTD. The
voltage drop across the RTD gets differentially mux'd, too. A 24-bit
delta-sigma ADC digitizes the voltage drop across the 270, then the
voltage across the RTD, and does the math. We're getting errors in the
tens of PPM, tolerable, but we're curious where they're coming from.
The sensitivity analysis math here is a nuisance.


John

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