SN65LVELT23: If not use one of input pins

Yuto Sakai

Part Number: SN65LVELT23

Hi,

I would like to know the connection when not using one of the input pins.
Should I connect to GND? Is there a problem with floating?

Best regards,
Yuto Sakai

over 5 years ago

0 David (ASIC) Liu over 5 years ago

TI__Guru**** 158296 points

Yuto-san

You would want to drive the unused input to a known state, either VCC or GND. The SN65LVELT23 has internal pullup/pulldown resistors, so you can leave input floating.

Please see this app note for more detail: http://www.ti.com/lit/an/slla082b/slla082b.pdf.

Thanks

David

0 Yuto Sakai over 5 years ago in reply to David (ASIC) Liu

Mastermind 6100 points

Hi David-san,

Thank you for you reply.
When the input pins is floating, is the output pin "high"? Or is it "Low"? Or "High" and "Low" repeat?

Best regards,
Yuto Sakai

0 David (ASIC) Liu over 5 years ago in reply to Yuto Sakai

TI__Guru**** 158296 points

Yuto-san

The SN65LVELT23 is a low-power dual GND Ground LVPECL/LVDS to LVTTL translator device. The device includes circuitry to maintain inputs at VCC/2 when left open.

Thanks

David

0 Yuto Sakai over 5 years ago in reply to David (ASIC) Liu

Mastermind 6100 points

Hi David-san,

Thank you for your reply.
When D0 and /D0 pins left floating, is the logic level of Q0 high? Or is it low?

Best regards,
Yuto Sakai

0 David (ASIC) Liu over 5 years ago in reply to Yuto Sakai

TI__Guru**** 158296 points

Yuto-san

If you want to guarantee the low on the output, then you need to add a weak pull resistor on the input. Please see this app note for more detail: http://www.ti.com/lit/an/snla051b/snla051b.pdf.

Thanks

David

0 Yuto Sakai over 5 years ago in reply to David (ASIC) Liu

Mastermind 6100 points

Hi David-san,

What is the state of the output if there is no weak resistor on the input?
Is the output tri-state?

I am concerned about causing crosstalk if the output is the operation that repeats Hi→Low.

Best regards,
Yuto Sakai

0 David (ASIC) Liu over 5 years ago in reply to Yuto Sakai

TI__Guru**** 158296 points

Yuto-san

The output may toggle. I would suggest putting the 50k pulldown on unused input to make sure the output stays low.

Thanks

David

Interface

Interface forum

SN65LVELT23: If not use one of input pins