AM26C32: Fail-Safe

Yuta Nishie

Part Number: AM26C32

Tool/software:

Hi,

Regarding the fail-safe function, the following thread states that it works in idle and open states.

https://e2e.ti.com/support/interface-group/interface/f/interface-forum/1202401/am26c32-reliable-fail-safe?tisearch=e2e-sitesearch&keymatch=AM26C32%2520fail#

Is it correct to assume that the fail-safe function works even if the differential input terminal is short-circuited? Or do I need to add a circuit for short-circuit protection?

Best Regards,

Nishie

7 months ago

0 Clemens Ladisch 7 months ago

Guru 316690 points

The description in the datasheet is not very precise; it does not say what "idle" means.

As shown in the functional block diagram, the A/B inputs have weak pull-up/-down resistors. This implies that the termination resistors would short the inputs, and that the fail-safe does not work for an idle+terminated or shorted bus.

0 Yuta Nishie 7 months ago in reply to Clemens Ladisch

Genius 4955 points

Hi Clemens-san,

Let me check if I understand your answer correctly.

・The AM26C32 failsafe function works only when the circuit is open.

・The failsafe function does not work when the circuit is idle or short. If protection is required, an external circuit must be added.

Best Regards,

Nishie

+1 Clemens Ladisch 7 months ago in reply to Yuta Nishie

Guru 316690 points

Correct.

Devices that have fail-safe receivers for open, idle, and shorts mention this explicitly in their datasheet. All modern transceivers have this, but they are one-channel devices.

0 Parker Dodson 7 months ago in reply to Yuta Nishie

TI__Guru 52132 points

Hi Nishie,

Clemens is correct - please let me know if you need any other help!

Best,

Parker Dodson

Interface

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AM26C32: Fail-Safe