MUX508: Unused pins

Takashi Onawa

Part Number: MUX508

Hi Team,

Could you tell me how we should deal with Unused pins of MUX508?
It can be left floating or both side should be tied to GND or Vcc?

Regards,

Takashi Onawa

over 3 years ago

0 Clemens Ladisch over 3 years ago

Guru 316760 points

[FAQ] More Frequently Asked Questions about signal switches and multiplexers says:

This training video answers this question for all potentially unused pins of a device: signal pins, control pins, VSS, No Connect pins, and thermal pads.

Switch control inputs must always have a defined state. If the device does not have internal pullup or pulldown resistors, the pin must be tied to a known voltage.

Switch signal input/output pins may be left floating. In high speed applications, best practice is to terminate these unused pins to GND.

0 Takashi Onawa over 3 years ago in reply to Clemens Ladisch

TI__Genius 13200 points

Hi Clemens-san,

Thank you for your prompt response on this.

OK, I understood that Digital "input" should tied to High or Low and doesn't care for analog lines.
I didn't find any description about internal pull up and down on Digital input pins. Could you tell me which is better for TMUS508, High or Low?

If there is pull down in it, tied to low is better to reduce the leakage.

Regards,

Takashi Onawa

+1 Clemens Ladisch over 3 years ago in reply to Takashi Onawa

Guru 316760 points

This device does not have internal pull-up or pull-down resistors.

+1 Tyler McGuire over 3 years ago

TI__Expert 3515 points

Hi Takashi,

The digital inputs (A0,A1,A2,EN) cannot be left floating but for unused source pins, they can be floated in lower frequency applications. For higher frequency or noise sensitive applications, we recommend that they be terminated to ground though a 50 ohm resistor. This will reduce noise coupling and cross talk.

On top of the video Clemens linked, we have an FAQ on the topic that can provide a more detailed explanation: [FAQ] What to do with Unused Pins & Exposed Thermal Pads?

Thanks,
Tyler

0 Takashi Onawa over 3 years ago in reply to Tyler McGuire

TI__Genius 13200 points

Hi Tyler-san,

Thank you for your supplemental explanation

Regards,

Takashi Onawa

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MUX508: Unused pins