Honored Contributor
Honored ContributorI think there are a few too many uncertainties here to be able to reassure you that it'll just work...
Yes, you can clearly drive pin 3 on the AE part to 3.3V. The first discussion is whether the AE part needs 3.3V on that VCC pin. Different devices distribute power to the fabric in different ways and many devices rely on power being applied to all power pins for correct operation. Remove power from one pin and bits of the device can stop working. I'm not saying that's the case with this device - I strongly suspect it isn't. If the four power pins are directly connected to each other internally then, clearly, the device won't need 3.3V sourced to pin 3. However, if that's the case, and your analyser does try assert PDn and place the part in sleep mode, then we're clearly heading for a problem. If the source impedance of that PDn signal is high, you'll be fine. If it's low then you're going to end up with a direct short, through the AE part, from power to ground (via the source of the PDn signal). Not so good. If you're really keen you could explore the source impedance of that signal and measure it. If you're happy that it's high enough then, even if the AE part is 'sourcing' 3.3V onto pin 3 (by virtue of a common power rail inside the device), and PDn is asserted low, then everything could continue to work, albeit without any power saving. On the contrary, we'll actually be burning more power, the power dissipated through the PDn driver circuit. However, measuring it's source impedance will rely on you being able to exercise the PDn signal - and you don't know if the you network tester even uses it. I look forward to your next instalment... Cheers, Alex
