I am trying to use the ADUM6400 isolation component with a LiIon battery. My Vcc is 3V for the rest of the circuit, however, for most power efficiency I would like to use the LiIon voltage (4.2V) for Vdd. This poses a problem in that my logic levels are at 3.0V. The datasheet is not very clear about the use of Vddl, but it seems like this pin can be used to set the logic levels. But then I read that Vddi and Vddl must be connected to the same external supply.
Please clarify. Can Vddl be different from Vddi in order to for me to use lower voltage logic signals? If not, is there a workaround such that I don't have to regulate Vddi down to 3.0V before powering the ADUM6400.
The ADuM6400 added the extra Vddl pin to give a supply pin that was somewhat decoupled from the tank switching noise internal to the part, not to add a new feature. We did not intend to have the supplies run at different volatges, so we have not characterized the device that way.
I spoke to the priciple designer and he thinks there is nothing preventing the part from being operated with Vddl at 3V and Vdd1at 4.2V. But it is not a configuration that we can guarentee performance, mostely because we have not checked it thoroughly. I would give it a try.
Thank you for your help.
Yes, indeed I hooked one up and tried it out.
The logic output on the "non-isolated" side of an ADUM6402 seems to
follow Vddl, and the inputs have thresholds that are also sensitive to
this same level, and not Vdd1. It looks like this part will be able to
do exactly what I need.