5V "tolerant" question about AD2

[Alfonz57]

I am interfacing the AD2 to an older component that runs at 5V. It has a high Vih level (4V) and I thought I could drive it with the pattern generator using external pullup resistors and the signals in open-drain configuration. This it what 5V tolerance implies. However, it appears the AD2 still has diodes to 3.3V even when driving open drain. Are the outputs, in fact, 5V tolerant, or does tolerance just mean that the inputs are protected against damage at 5V?

Thanks for your response.

[attila]

Hi @Alfonz57

The DIOs are protected up to +/-20V, See the following:
https://digilent.com/reference/test-and-measurement/analog-discovery-2/hardware-design-guide#digital_io

[Alfonz57]

Thanks for the response! Reference diagram explains all.

[LHji]

We had a Analog Discovery 2 board.   We have the following questions about this 5V "tolerant":

1. Can we use "Open drain" with a pull up resistor to translate the digital output to 0 or 5V?  

2. Can we use "open drain" for IO pin that is configured as clock or pulse?

3.  What is the recommend pull up resistance value? 

 

Thanks

[attila]

Hi @LHji

1. As you can see here the DIOs have 220R series and diodes to 3.3V and GND.
https://digilent.com/reference/test-and-measurement/analog-discovery-2/hardware-design-guide?digital_io#digital_io

2. Yes.

3. It depends what high/low voltage and rate you want. With 1k pullup you will have about 4V high and 1V low, with 10k 3.5V and 0.1V