DS26LV32AT - Can differential input be left floating?

Andrea Ramos

Other Parts Discussed in Thread: DS26LV32AT

Hello,

Will it affect the result of the single-ended output (LVTTL) if I leave the low side of the RS-422 differential input unconnected (floating)?

The RS-422 line receiver that I use has the part number DS26LV32ATM.

Thanks for your help.

over 11 years ago

0 T.K. Chin over 11 years ago

TI__Expert 3175 points

Hi Andrea,

DS26LV32AT has "Receiver OPEN fail safe" feature. When the differential inputs are left open, the output is logic High. Please see Truth Table on page 2 of the datasheet.

regards,

TK Chin

0 Reagan Revisore over 11 years ago in reply to T.K. Chin

TI__Expert 4225 points

TK,

Is this still the case when only one of the inputs are left open?

-Reagan

0 Michael Lu (Santa Clara) over 11 years ago in reply to Reagan Revisore

TI__Mastermind 29655 points

Hi Reagan,

This part was designed for differential and not single-ended input operation. In which case would there only be one input left open?

Thanks,

Michael

0 T.K. Chin over 11 years ago in reply to Michael Lu (Santa Clara)

TI__Expert 3175 points

Hi Reagan,

There is internal bias to support the open fail safe feature. One input pin is pulled a little positive than the other pin through internal biasing. This ensures logic high at output when both inputs are open.

If there is only one pin open, there is no guarantee the output will be at logic high.

Regards,

Interface

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DS26LV32AT - Can differential input be left floating?