Using Multiplexer 74HCT4053

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Hi, i want to use multiplexer chip for ADC. To measure voltage and current. ADC is LTC2420. As im using only one switch in it (its a Triple 2-channel multiplexer) i don't know what to do with others (datasheet not tells anything about unused pins). Can they all be grounded? As im using 2Y0, 2Y1, 2Z and S2 pins other select pins also can be grounded?

Thank you.

[singapol]

The general guideline is unused cmos outputs can be left floating but unused inputs must be connected to VCC(power supply) or ground.

Questions about cmos ic:   http://toshiba.semicon-storage.com/ap-en/design-support/faq/logic.html

Designing with logic:  www.ti.com/lit/an/sdya009c/sdya009c.pdf

https://www.fairchildsemi.com/application-notes/AN/AN-77.pdf

http://electronicdesign.com/boards/save-power-managing-unused-cmos-io-pins

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Yep. i tryed on scope how signal looks on floating select pins channels. It looks like WAV to MP3 conversion  (its picking 50Hz and swiching on and off

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Anyone can tell is it good layout for ADC or can give some advises how it can be improved?

[ebclr]

Maybe is to late but this can be bougth

http://www.ti.com/lit/ds/symlink/ads1226.pdf

[JPortici]

The Selector input is a CMOS digital input and as such it must be connected to a digital 0 or 1, so to VCC or GND.
I guess you could leave the analog channel floating, but i would ground every pin just to be sure nothing gets picked up ann injected to other channels

It looks like WAV to MP3 conversion

Huh?

[xoom]

Maybe is to late but this can be bougth

http://www.ti.com/lit/ds/symlink/ads1226.pdf

I already have that ADC so not planing to buy another

The Selector input is a CMOS digital input and as such it must be connected to a digital 0 or 1, so to VCC or GND.
I guess you could leave the analog channel floating, but i would ground every pin just to be sure nothing gets picked up ann injected to other channels

It looks like WAV to MP3 conversion

Huh?

S2 will be connected to Atmega.. im just thinking now about analog part (ground plane and voltage inputs, also VCC)

O.T. Analog sound to digital sound it just stuck in my memory when i seen similar image with that presentation

[Ian.M]

Unless charge injection and stray capacitance are serious issues, I'd simply wire all three '4053 switch sections and their control inputs in parallel for lower on resistance.

[Kleinstein]

With the LTC2420, the GND layout could be critical. As the HC4053 does not use a lot of current the layout is still OK. One might want a capacitor to GND from the input of the LTC2420.

The trimmer in the circuit looks a little strange - usually one would use numerical adjustment instead of a drifting analog trimmer.