Pogo pins power clarification - reading schematics
01-06-2021, 11:33 PM
Thanks both for the replies. Forgive me if I seem stubborn. Still want to talk through this if you'll humor me :-)
I'm not asking about any single use case, but want to understand what PIN1 and PIN5 are and how they work. I'm sure that we can power an expansion board from pogo pins, we can set that aside as a given.
Makes sense to me, I agree.
I follow you that it's on the same rail. Pogo PIN1 goes directly to the PMIC's power inputs ACIN and VBUS. The USB C connector's VBUS pins also go directly there.
By "no protective element in between", you mean none between pogo PIN1 and the USB C connector? I agree. What doesn't make sense is why you couldn't power the phone from PIN1 (given USB C is not connected). I don't see any logic there to distinguish PIN1 from the USB C connector's VBUS. It's the same DCIN signal on the schematics.
Imagine a scenario: Powering a lone mainboard. There would be no USB-C smallboard attached via the 40-pin connector. Would it now be safe to connect a 5 V source to pogo PIN1?
Another scenario: this "wireless coil design used in the back case" from the december blog update. The may blog update even says "Wireless charging coming to the PinePhone via add-on / using pogo pins". My guess was the wireless charger provides 5 V to PIN1/DCIN.
Some investigation with a multimeter:
With a powered down PinePhone, I get 0 V from PIN5 and 4.0 V (battery voltage, unloaded) from PIN1.
Power up the PinePhone with no charger in the USB C port. I get 0 V from PIN5 and 3.9 V (battery voltage, loaded, modem is off) from PIN1.
PinePhone still powered on, now I plug in a USB C charger. I get 5.0 V from PIN5 and 4.8 V from PIN1.
As I understand it, 4.8 V is the voltage of my external AC to DC power brick in the wall under whatever load. I don't _think_ that's the voltage at which the battery gets charged. I think the max allowed for charging a Li battery is around 4.2 or 4.3 V, and anyways, since this battery is almost full, it's probably in the constant-voltage phase of charging. Maybe I'll hook up to a variable power supply to investigate more.
What I'm hearing is that if you're powering an expansion board from the PinePhone's pogo pins, you can pick between a 5 V source or the battery voltage. But what I'm measuring is that if you pick PIN5, you get 0 V or 5 V depending on whether or not USB-5V is enabled. If you pick PIN1, you get either the battery voltage or the USB C connector's voltage, depending on whether or not an external power source is plugged in.
I noticed something else. Without the charger plugged in to the USB Type-C port. So if you use PIN1/DCIN as an output from the PinePhone. Power is going from the battery into the PMIC, and then out of the PMIC's ACIN and VBUS pins? The AXP803 data sheet says ACIN and VBUS are type "PI" (I think Power Input). Is that drawing power "backwards" through the PMIC?
I'm not asking about any single use case, but want to understand what PIN1 and PIN5 are and how they work. I'm sure that we can power an expansion board from pogo pins, we can set that aside as a given.
(01-06-2021, 04:33 AM)scholbert Wrote: USB-5V is delivered from a DCDC-regulator and used in general to power attached USB devices with the Pinephone is in the role of the host.
In this case it is switched to USB Type-C connector.
When using USB-5V as a power rail it should definitely be used as a power source coming from the Pinephone.
It could be controlled by GPIO PD8-VCC5V_EN
Makes sense to me, I agree.
(01-06-2021, 04:33 AM)scholbert Wrote: As DCIN is directly connected to the USB Type-C port it's on the same rail.
From my point of view it should not be used to power the phone or charge the battery, because it may conflict with an attached USB Type-C charger.
Powering DCIN from the pogo pins, conflicts with the logic inside the phone and there's no protective element in between.
I follow you that it's on the same rail. Pogo PIN1 goes directly to the PMIC's power inputs ACIN and VBUS. The USB C connector's VBUS pins also go directly there.
By "no protective element in between", you mean none between pogo PIN1 and the USB C connector? I agree. What doesn't make sense is why you couldn't power the phone from PIN1 (given USB C is not connected). I don't see any logic there to distinguish PIN1 from the USB C connector's VBUS. It's the same DCIN signal on the schematics.
Imagine a scenario: Powering a lone mainboard. There would be no USB-C smallboard attached via the 40-pin connector. Would it now be safe to connect a 5 V source to pogo PIN1?
Another scenario: this "wireless coil design used in the back case" from the december blog update. The may blog update even says "Wireless charging coming to the PinePhone via add-on / using pogo pins". My guess was the wireless charger provides 5 V to PIN1/DCIN.
Some investigation with a multimeter:
With a powered down PinePhone, I get 0 V from PIN5 and 4.0 V (battery voltage, unloaded) from PIN1.
Power up the PinePhone with no charger in the USB C port. I get 0 V from PIN5 and 3.9 V (battery voltage, loaded, modem is off) from PIN1.
PinePhone still powered on, now I plug in a USB C charger. I get 5.0 V from PIN5 and 4.8 V from PIN1.
As I understand it, 4.8 V is the voltage of my external AC to DC power brick in the wall under whatever load. I don't _think_ that's the voltage at which the battery gets charged. I think the max allowed for charging a Li battery is around 4.2 or 4.3 V, and anyways, since this battery is almost full, it's probably in the constant-voltage phase of charging. Maybe I'll hook up to a variable power supply to investigate more.
What I'm hearing is that if you're powering an expansion board from the PinePhone's pogo pins, you can pick between a 5 V source or the battery voltage. But what I'm measuring is that if you pick PIN5, you get 0 V or 5 V depending on whether or not USB-5V is enabled. If you pick PIN1, you get either the battery voltage or the USB C connector's voltage, depending on whether or not an external power source is plugged in.
(01-06-2021, 04:33 AM)scholbert Wrote: USB-5V and DCIN should be used to power your extension board... so, yes they should be seen as outputs.
(01-06-2021, 04:33 AM)scholbert Wrote: Without a charger connected to USB Type-C DCIN is normally not present
I noticed something else. Without the charger plugged in to the USB Type-C port. So if you use PIN1/DCIN as an output from the PinePhone. Power is going from the battery into the PMIC, and then out of the PMIC's ACIN and VBUS pins? The AXP803 data sheet says ACIN and VBUS are type "PI" (I think Power Input). Is that drawing power "backwards" through the PMIC?
