AM26C32: Encoder Interface

Brian Wang0928

Genius 14030 points

Part Number: AM26C32

Customer is now using competition MAX14890E device on Encoder interface with HTL and TTL receivers.

Is AM26C32 able to support TTL and HTL? Or what else new one you recommended? thanks.

over 2 years ago

0 Clemens Ladisch over 2 years ago

Guru 316470 points

Single-ended TTL and HTL signals are just logic signals. Is support for differential TTL/HTL signals required?

0 Brian Wang0928 over 2 years ago in reply to Clemens Ladisch

TI__Genius 14030 points

You can refer to below one from competition. it's diff. input receiver.

0 Parker Dodson over 2 years ago in reply to Brian Wang0928

TI__Guru 52052 points

Hi Brian,

The AM26C32 Single ended outputs do meet TTL at 5V as the VOH(min) =3.8V and the VOL(max) = 0.3V so those should conform to TTL levels okay.

For an input value - you would need to bias the "-" input to half of the max signal received from the TTL driver so that the AM26C32 can see a negative and positive value and if those values are <-200mV for 0 and >200mV for 1 than it would work - but you will not get any distance with TTL outputs and so this output is going to limit the length of the system. So ultimately it may be possible - but you will have to add circuitry to make it feasible and it will still have reduced performance comparted to RS-422 standard.

This is our recommended part for this type of application still.

Please let me know if you have any other questions!

Best,

Parker Dodson

0 Brian Wang0928 over 2 years ago in reply to Parker Dodson

TI__Genius 14030 points

Thanks Parker.

In the most Encoder application, it would need various interface for RS422/HTL/TTL like MAX14890E with SE or Diff type inputs.

Does team have plan to develop such device and dedicated for Encoder?

Regards

Brian

+1 Parker Dodson over 2 years ago in reply to Brian Wang0928

TI__Guru 52052 points

Hi Brian,

At this time I do not think so. I will also note - we really don't do RS-422 anymore, explicitly anyway as RS-485 is generally preferred for its improved performance.

We haven't really been doing multi-channel (>2 channels) devices for a decade + so I wouldn't hold your breath waiting. The best option from us is the one I mentioned - but its not exact - we don't have a direct match.

Best,

Parker Dodson

0 Brian Wang0928 over 2 years ago in reply to Parker Dodson

TI__Genius 14030 points

Thanks.

Customer don't think the AM26C32 is able to support HTL. is this statement correct?

Regards

Brian

0 Clemens Ladisch over 2 years ago in reply to Brian Wang0928

Guru 316470 points

Not without additional components. (Any differential receiver can be made to read a single-ended signal by connecting a reference voltage of (high+low)/2 to the inverting input.)

+1 Parker Dodson over 2 years ago in reply to Brian Wang0928

TI__Guru 52052 points

Hi Brian,

You can - but not without additional components - it doesn't automatically conform to HTL - you would need to connect a reference voltage to the inverting input as Clemens described - but it should be possible - but not necessarily advisable.

Please let me know if you have any other questions!

Best,

Parker Dodson

0 Brian Wang0928 over 2 years ago in reply to Parker Dodson

TI__Genius 14030 points

Thanks. Is there circuitry to achieve this HTL with AM26C32 to share?

Regards

Brian

0 Clemens Ladisch over 2 years ago in reply to Brian Wang0928

Guru 316470 points

See section 5 and figure 2 of AN-972 Inter-Operation of Interface Standards.

0 Parker Dodson over 2 years ago in reply to Brian Wang0928

TI__Guru 52052 points

Brian,

The document Clemens linked is the best resource we have for these types of applications.

Best,

Parker Dodson

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AM26C32: Encoder Interface