QWe are developing an evaluation board for our custom designed ic (ASIC) and we
are planning to use the Digital Isolators ADuM3480
There is a detail in the datasheet, which we don't understand:
It says on Page 12 that the default output state can be chosen to be high or
low by pulling the Input Ctrl2 high or low.
On page 17 it says that "If the decoder receives no pulses for more than about
5 μs, the input side is assumed to be unpowered or nonfunctional, in which case
the isolator output is forced to a default low state by the watchdog timer
We are irritated that it is not mentioned on page 17 that the default State can
be chosen. It says, that he can only be low. And we would like to ask, if the
default state on page 17 is the one which can be selected on Ctrl2. Do this two
descriptions talk about the same thing of does the Ctrl2 does not has anything
to do with this default state after 5ms?
And the other question which is very important for us: Do we understand it
correctly, that the ic is not desiged to keep a digital output on the same
level as its input for longer than 5ms, because after 5ms the output changes to
the default level if no digital transition happens on the input?
AOn page 17 the “low” should be replace by the word “selected”.
Yes, Ctrl2 selects the value of the default state as it says in the pin
description. It was a text reuse issue, since many of our parts do not allow
selection of the default state it was copied and not corrected.
You are correct, if power is removed from side 1 the last state through the
coupler will be valid for a maximum of 5uS (microseconds, not milliseconds)
then it will switch to the default state set by pin Ctrl2.