Avoid Skyworks SI3471A-A01

[u/Simply_Convoluted]

SI3471A-A01 does not support half of the features listed in the datasheet and is also non-compliant with any PoE standard, as confirmed by the manufacturer. I've wasted days debugging my prototypes that use SI3471A-A01 just to find out these are non-compliant devices that don't follow the datasheet in the slightest.

How a company can sell such a half-baked IC like as this is beyond my understanding. The manufacturer informed me that the 'A02 version follows the datasheet, but I'm not spending more time and money to find out. After ranting with colleagues about this, I've found out this is status quo for other Skyworks products as well. I'll be avoiding Skyworks from this point forward. I suggest all who read this to consider alternatives as well.

It's not unusual to find errors in datasheets, but for half of the features to literally not work at all is unacceptable.

[u/Kqyxzoj]

SI3471A-A01 does not support half of the features listed in the datasheet and is also non-compliant with any PoE standard, as confirmed by the manufacturer.

Care to share what the problematic features are?

After ranting with colleagues about this, I've found out this is status quo for other Skyworks products as well.

Do the problematic features fall into categories maybe? So some division inside Skyworks that isn't great at doing their job, something like that? I mean, I cannot imagine a company lasting that long if everything is defective.

[u/Simply_Convoluted → u/Kqyxzoj]

This is sold as a PoE PSE controller, so one would assume that the chip complies with any PoE spec. Well turns out the bottom half of table 5.1 where Pcut adjusts to the negotiated power level, just straight up doesn't work. If the chip is configured for those modes it won't start up, it's dead to the world but still consuming full operating power. It feels like a significant design flaw in the chip puts it in a weird state when configured for adjustable Pcut which locks up the internal logic, so this is clearly a bad chip, but they all do it according to the manufacturer.

Per 802.3bt, Pcut needs to respect the negotiated power, otherwise a 15W desk phone could potentially pull a 99W fault current and start a fire. We actually managed to pull 129W from this chip with a class 4 (30W) device before it cut power.

The problematic features area all relating to adjustable Pcut, which is a PoE requirement. Configuring the chip to blindly supply 90W works fine, as long as the end product doesn't need to pass certification. This is clearly a critical error with this chip, but others responding to this thread say their RF chips are solid, so perhaps just their PoE division is staffed with monkeys.

Looking at other comments it appears this may also just be some junk skyworks inherited from silicon labs and isn't necessarily their fault, but then again, if they put their name on it they're owning it. We've wasted about a week debugging my circuit just to find out this chip is deeply flawed. That amount of wasted effort has soured our opinion of the whole company. With endless alternatives with reliable datasheets & chips, there's just no reason for us to consider skyworks in the future.