USB-6501 1.5V Output through Open Drain Configuration?

[BobDizzle]

Hello,

I was looking to use a the 6501 to drive a parallel addressing bus that has a 1.5V nominal logic high (yeah why?).  Is there any reason I can't use a 1.5V supply with a bunch of pull-ups to accomplish this?  Looks simple enough to me just want to make sure I'm not missing anything.

Thanks,

Bob  

[K C]

Hi,

It looks simple enough 2 resistors for each output. Choose the right value and the 0-5V is converted to 0-1.5V.

But there is a catch. How much current is the address input sourcing when the input is a '0'

That reverse input current will cause the input voltage to rise a bit. Normally no problem but with 1.5V input it is more critical.

Do you have the specification of the input(s) connected to the addresses ?

Kees

[BobDizzle]

Working with the designers to determine the thresholds and the characteristics of the addressing circuitry.  I guess my question was more along the lines of "can the internal 5V reference be shut off?"

[K C]

Don't think that is possible. But like I explained the 5V is not a problem.

Kees

[PatQ]

Hi, I wan to use the USB-6501 as open drain, but without the 5V output. Like (high imp - open drain). By software is it possible? Or by HW? I drive 3.3V and some 1.8V. Anyone found a solution.

Thanks,

Patrick

[santo_13]

Yes, you can configure the channels as open-drain or push-pull through software.

You can configure this feature using the below property node

[PatQ]

Hi Santo_13,

I already read this, did you try it in open drain without the 5V. Because of the 5V pull up in the circuit I'm not able to eliminate it by software. Only if I remove the Rx pull up, I'm able to use it in open drain without the 5V output if the logic is 1. But it's not what I wan to do.( 2 x DIO x 24 port x 16 test stations).

If you know by software please let me know.

Thanks,

Patrick

[santo_13]

Now I get your concern, no, you cannot disable the internal pullup to 5V as stated in the manual.

Your options,

1. Use an external open-drain buffer, like this https://www.ti.com/lit/ds/symlink/sn74lvc1g07.pdf?ts=1622567899185&ref_url=https%253A%252F%252Fwww.t...
2. Open up 6501 and desolder all those pull-up resistors but it may interfere with DI functionality or other features.

[PatQ]

Hi Santo_13,

Thank you very much!

I will check what it's better for me.

Have a nice day,

Patrick