Power consumption

Hi Fizzl,

  These current levels are normal and with expected levels for this part. See page 4 of the datasheet, where the expected Vcc supply current with the bus unloaded can range from a typical of 20mA up to 53mA, so your ~30mA is right in the range.

The ADM2582 uses a different isolated power supply circuit which is more efficient, but it is also a stronger source of common-mode emissions and so requires a careful PCB layout with multiple layers to form stitching capacitor to control these emissions.  The ADM2863's power supply circuit is greatly improved from the power supply's common-mode emissions perspective, but this improvement comes at the cost of a greater supply current.

  Unfortunately this part doesn't natively offer a lower power standby option.  If your application is able to tolerate the approximately 10ms start up time for the power supply, you could add a switch/pass transistor to switch the Vcc supply on and off.  It is OK to leave VIO powered and if DE and TxD are both low, the supply current will be less than 1mA.    If you implement this mode, I'd suggest also making sure that nRE is pulled high so that RxD is put into a high-Z state.

Eric

Hi Eric,

thank you for your detailed answer. I was pretty much expecting this after all my tests and, as you said, as the datasheet already mentions this. But as the ADM2582s datasheet states >100mA in some scenarios I wanted do be sure that i haven't missed anything here. 

Good to know that I can turn it off that way. I'll try that and see what the consumption is after that - additional 10ms are no problem here.

As an alternative, is there a low-power isolated 485 IC that would fit (ideally) this footprint and maybe even as a drop in replacement?

Thanks

Fizzl