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SN74CB3Q3257: Example circuit not works according Proteus simulation

albgarc2014
Genius 3480 points
Part Number: SN74CB3Q3257

Tool/software:

Hi TI:

I need to read 8 resistive dividers with a MSP432. I only have available 4 analog pins of the MSP432, I plan to multiplex through a SN74CB3Q3257PWR according to the attached schematic.

However in a proteus simulation (without the MSP432, leaving the common outputs 1A, 2A, 3A, 4A floating and biasing directly to OE and S), I don't get the correct voltage values on the common outputs 1A, 2A, 3A and 4A.

Do you see the correct use of the SN74CB3Q3257PWR or do you see some error in the design?

Thanks very much.

Best Regards.

  • +1
    Guru 298500 points

    As far as the switch is concerned, the schematic looks OK.

    I do not know what your Proteus simulation does. Try adding a load.

    The MSP432 SAR ADC inputs have quite a low input impedance, it might be necessary to buffer the inputs, at least with a capacitor.