SN65LVDT388A: Pin compatible part with active fail-safe

Patrick Ruf

Part Number: SN65LVDT388A
Other Parts Discussed in Thread: SN65LVDS32B, DSLVDS1048

Hi,

We use the part SN65LVDT388ADB in one of our application. Now we have the problem that under certain circumstances the inputs can get shorted to GND.
Does TI has a pin compatible part with active fail-safe (like e.g. SN65LVDS32B)?

If there is no pin compatible part what would be the best (closest) alternative with active fail-safe?

Thanks and best regards,

Patrick

over 2 years ago

0 Malik Barton57 over 2 years ago

TI__Guru 64326 points

Hi Patrick,

My apologizes for the delay. Unfortunately we do not have a 8 channel receiver with active fail safe. There are only 4 channel alternatives like SN65LVDS32B or DSLVDS1048.

0 Patrick Ruf over 2 years ago in reply to Malik Barton57

Genius 4810 points

Hi Malik,

Thanks for your answer. Further investigations showed that the inputs do not get shorted to GND but it is possible that they have weak pulldown resistors on them. Therefore the Receiver Open-Circuit Fail-safe circuit (chapter 10.3.2) from datasheet is interesting. Now I have one more question:
What could be the worst case VIT (threshold) max voltage? In the datasheet only an approximat value of 2.3V is mentioned.

Regards,
Patrick

0 Malik Barton57 over 2 years ago in reply to Patrick Ruf

TI__Guru 64326 points

Hi Patrick,

I am sill looking into this for you, sorry for the delay. I will update you when I can find more information. Are you interested in the max or min voltage? I believe worst case min VIT would be more applicable here.

0 Malik Barton57 over 2 years ago in reply to Malik Barton57

TI__Guru 64326 points

Hi Patrick,

Max VIT here would be 3.3V or Vcc and VIT ABS max is 4V.

0 Patrick Ruf over 2 years ago in reply to Malik Barton57

Genius 4810 points

Hi Malik, maybe there is a misunderstanding. On page 17 in the datasheet it is written "VIT≈2.3 V". So we need to know the range that VIT (internal threshold voltage) can have.

Regards,
Patrick

0 Clemens Ladisch over 2 years ago in reply to Patrick Ruf

Guru 264040 points

The recommended operating conditions imply that the highest valid input voltages (with a differential input voltage of 0.1 V) are 2.3 V and 2.4 V. So the V_IT of 2.3 V appears to be too low.

Anyway, how weak are the pulldowns? They would have to be much larger than 300 kΩ, or you would need to add stronger pullups.

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SN65LVDT388A: Pin compatible part with active fail-safe