ADUM315x / ADUM3151 / ADUM3152 / ADUM3153 speedgrade question

Hello together,

I have a question concerning ADUM315x parts and speedgrade A and B:

In datasheet you can find the followoing information:

Later in technical description of the datasheet there are more detailed information;

So my question why is speedgrade A specified for 1MHz only? If glitch filter is the only difference between those parts maximum speed should be higher and not differ so much to speedgrade B. We have tested to clock ADUM3151

A with more then 1MHz (up to 5MHz) without having a problem in communication. In that case propagation delay is still smaller then clock frequency.

Anyhow we doubt to do that because when refering to datasheet we would operate the part beyond specification.

Could you provide some more information concering that issue? When using information provided in should be a problem to increase data rate a speed grade A type.

Thanks in advance


[edited by: intec at 10:41 AM (GMT 0) on 6 Feb 2019]