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Released September 16, 2016. Models A1661, A1784, and A1785. Available in 32, 128, or 256 GB configurations in Rose gold, gold, silver, black, jet black, and (Product)Red.

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What is the purpose of Q2102 FET on SWI line?

hey

in older iphone models SWI line go directly to Charging IC ,But in Iphone 7 plus there is a kind of FET (Q2102) on SWI line , So what the purpose of this?

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I don't have an iPhone 7 on hand to probe the circuit but my reading is as follows:

  • Q2102 is an n-type enhancement mode MOSFET. The Source-Drain channel is normally "open-circuit" although there is a body diode that allows current to flow in one direction but not the other.
  • When PP1V8_SDRAM comes on, then the MOSFET is turned on and the channel closes. The Battery_SWI signal can now freely flow from the battery to TIGRIS.
  • When PP1V8_SDRAM goes to 0V (turning off the phone), the the channel opens up again and the Battery_SWI signal can no longer communicate to TIGRIS.

Why did Apple make this change? Who knows, perhaps they had some data to back up the assertion that some batteries (read: cheapo batteries) were sending spurious signals directly to TIGRIS and causing an unacceptable defect rate. Maybe that was the issue behind the "unexpected shutdown" recall for the iPhone 6S.

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So does that mean in iphone 7 model a battery type detection may be integrated?

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All TIGRIS enabled devices already had a battery sense line (see pin E1 - BAT_SNS).

Interestingly, the iPhone 6 did not have the FET but rather a direct connection to the battery gauge via a filter (FL2511). Starting with the iPhone 6S, the filter is gone and replaced by an RC Filter configuration, filtering out anything above ~30MHz, and feeding it.

Perhaps even more interesting is that on the iPhone 6S/6S+, the FET is in line with the HDQ_HOST pin of TIGRIS whereas on the iPhone 7/7+, the FET is in line with the HDQ_GAUGE pin. I suspect there is an error on one of the two schematics but unfortunately I don't have an iPhone 7 on hand to check.

So take what I say in my answer with a grain of salt. It makes sense electronically but I can't say for sure if this is indeed the way it's connected on the logic board.

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