Hi,
I’m using birdirectional digital isolator for the first time. I completely missed that the bidirectional pins of the isolator are open-drain. I see the datasheet says that I need to use pull-up resistors. I need help selecting corrrect vales of them. I did calculated and it seems to me that they are low than the value of usual pull-up resistor.
Any help is highly appreciated.
Thanks.
Greetings,
A suitable pull-up resistor value would depend on a number of factors, chiefly the amount of capacitance on the line and how fast one wants to go. All the current for charging any connected capacitance during a low-high transition has to go through the P/U resistor; too-high values will cause the signal edges to round off excessively and wreck your timing. Too low, and one burns more current than necessary. The limiting value for the affected pins appears to be 50mA, so that gives you a floor value based on the supply voltage used.
The datasheet does offer some guidance and reference info on the matter, but ultimately you’ll probably want to 'scope the result in action and verify that you’re not uncomfortably close on the timings.
