Am I understanding this circuit right?

[caphair]

This is from an iPhone 6. I'm having a hard time understanding how q1401 controls the "handshake" to Tristar_pin to allow charging.

I don't see anything controlling the gate of q1401 either. Am I write to assume current flow that I've traced in red?

[budm]

Re: Am I understanding this circuit right?

Do you mean Q1701?
Voltage Source is fed to the Source pin of that P-CH MOSFET (Positive is applied to SOURCE pin so DRAIN has to be less positive than the SOURCE pin), when the Gate Voltage is 3~5V below the Source the MOSFET will be turned on then you will have Voltage at the Drain pin.
Do you see that NETLIST named 'REVERSE GATE'? That pin goes to other circuit that has the same NETLIST name that you need to find, that will be what control the MOSFET, that NETLIST named 'REVERSE GATE' may go to more than one place.
May be you should upload the whole schematics for people to see.

[caphair]

Re: Am I understanding this circuit right?

Here is full schematic. I don't see netlist 'reverse gate' anywhere. Even searched entire PDF

[budm]

Re: Am I understanding this circuit right?

That NETLIST 'REVERSE GATE' has to be some where in the schematics.
That one page Schematic is not going to be enough.

[caphair]

Re: Am I understanding this circuit right?

That NETLIST 'REVERSE GATE' has to be some where in the schematics.
That one page Schematic is not going to be enough.

I've searched the entire PDF of iPhone 6 and did not find another 'reverse gate' net. There aren't even any page numbers next to it indicating where else it would be found in the PDF. I'm puzzled as well

[budm]

Re: Am I understanding this circuit right?

BTW, so what DCV do you have right now at S, G, and D?

[stj]

Re: Am I understanding this circuit right?

look more closely.

the fet is bypassed with a diode to allow INCOMING power to reach the chip,
the fet is only used to enable OUTGOING power for USB-OTG use.

[caphair]

Re: Am I understanding this circuit right?

look more closely.

the fet is bypassed with a diode to allow INCOMING power to reach the chip,
the fet is only used to enable OUTGOING power for USB-OTG use.

Could you explain this more?

@budm I don't have one to test I'm just trying to understand the operation

[stj]

Re: Am I understanding this circuit right?

usb-otg = a usb port that can act as a master supplying power, or a slave like a memory stick.

the device needs to be able to detect 5v on the connector to know if it's plugged into a pc,
but also needs to be able to power it up with 5v incase you connect a memory stick etc.

[caphair]

Re: Am I understanding this circuit right?

So the p_in terminal acts both as an input and output? It's confusing because it's tagged "p_in" and the line "handshake" so makes me think USB 5v flows into it.

But if q1701 is a p channel then the source pin (Tristar) would mean 5v USB is being provided to the drain

[stj]

Re: Am I understanding this circuit right?

i would need the full schems.
what's your interest anyway? curiosity - or a faulty fone?

[caphair]

Re: Am I understanding this circuit right?

Curiosity. Trying to figure out how that chip knows you're using a genuine Apple charger. As I've read the Tristar chip is responsible for that and I see "handshake pin" on that line

[stj]

Re: Am I understanding this circuit right?

that's easy,
there are resistors between the power and data pins.
the combination of resistances tells the fone what charger your using.

this was originally done by blackberry btw, so the fone would not "boost-charge" itself when plugged into a pc and trash your usb ports!

[stj]

Re: Am I understanding this circuit right?

look at this:
there is a table on page16

[caphair]

Re: Am I understanding this circuit right?

Oh geez so what's all that "handshake" pin stuff about? I was under the assumption that because an Apple lightning cable had an integrated chip in it that it operated more complexly

[gabiz_ro]

Re: Am I understanding this circuit right?

Note that genuine Apple charger is charger
Lightning cable is ... cable.
For charger stj is right.Just resistors.
But for lightning there is more complicated things.
More info on http://ramtin-amin.fr/#tristar

[caphair]

Re: Am I understanding this circuit right?

Note that genuine Apple charger is charger
Lightning cable is ... cable.
For charger stj is right.Just resistors.
But for lightning there is more complicated things.
More info on http://ramtin-amin.fr/#tristar

Ah yes I was referring to the cable. My mistake. It does look somewhat complex.

So in my original post, are the red arrows I drew the wrong way current flows into that line?

[gabiz_ro]

Re: Am I understanding this circuit right?

On the phone is little hard to follow schematics.
But from a quick look I don't see any protection to reverse voltage.Could be in dock flex connector,but not sure.
Also looking on 5S schematic,looks similar and 5V usb protect.
As result if voltage right aplied tristar may enable charging and usb data,if reverse voltage aplied tristar disable charging and other circuits to protect.

[caphair]

Re: Am I understanding this circuit right?

On the phone is little hard to follow schematics.
But from a quick look I don't see any protection to reverse voltage.Could be in dock flex connector,but not sure.
Also looking on 5S schematic,looks similar and 5V usb protect.
As result if voltage right aplied tristar may enable charging and usb data,if reverse voltage aplied tristar disable charging and other circuits to protect.

What do you mean by reverse voltage applied?

[gabiz_ro]

Re: Am I understanding this circuit right?

Reverse voltage,when you doesn't use genuine cable,chargers,etc.
When right is + to + and gnd to gnd,is right,reversed when reversed.
If you take a look at iPhone schematics from iPhone 3 to newer ones,you'll see that first ones use two transistors.If voltage applied right,then 5V from USB or charger reach to phone internals.If wrong or reversed voltage applied,then nothing.

Seems like newer ones doesn't care if power line are reversed so only protect circuit is for tristar,if OK will power if not just do nothing.

Seems hard to explain,but take a look at +5V from USB on iphone 3,3GS,4,4S...
On all seems to be something that prevent reversed polarity,on 6 except circuit you ask in first post,nothing.

This is not first post where you ask something iphone related.
As you may noticed,for many components there is no generic info or datasheets available.
So we may only guess what is about this.

Short answer.
Tristar P_IN pin needs to be powered with +5V to start charging and power on.
Why? I don't know since I can't see or find tristar datasheet.