SN75179B: Unused differential input pin

Hisao Uchikoshi

Genius 14870 points

Part Number: SN75179B

Hi Experts,

When we do not need RX side, can we tie pin 7 and 8 to GND and leave 2pin open?

regards,

Uchikoshi

over 3 years ago

+1 Clemens Ladisch over 3 years ago

Guru 316760 points

Unused outputs can be left open.

Differential inputs should be tied to different voltages; otherwise, the input is at the switching threshold and can lead to oscillations. But this device has hysteresis, so oscillations cannot occur. (But tying one input to V_CC anyway cannot hurt.)

0 Hisao Uchikoshi over 3 years ago in reply to Clemens Ladisch

TI__Genius 14870 points

Thank you for your answer.

Can we connect A pin and B pin to VCC and GND directly? Or Should we add pull-up/pull-down resister?

+1 Clemens Ladisch over 3 years ago in reply to Hisao Uchikoshi

Guru 316760 points

Resistors are not necessary.

+1 Eric Schott1 over 3 years ago in reply to Clemens Ladisch

TI__Guru 53555 points

Thanks Clemens!

Hi Hisao,

Biasing resistors would decrease the leakage current through the unused pins if you would like to same some extra power. If this is not a concern, a direct connection is also fine as Clemens suggests.

Let us know if you have any more questions.

Regards,
Eric Schott

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SN75179B: Unused differential input pin