Got my laptop recently and it took me a couple days (and a few cables) to realize the charger I was using was the issue. It’s output specifications are
USB PD Output: 5V=3A/9V=3A，15V=2A/20V=1.5A
I don’t have a lot of knowledge of how the negotiations work but is there a reason that the laptop isn’t opting for the 20V?
This charger was only supposed to be a temporary measure until my dedicated charger arrived but the dedicated charger has the specifications:
DC 5V/3A, 9V/3A, 12V/3A, 15V/3A, 20V/3.25A
so I’m worried that might also be fall into the same trap.
@fishghost How are you determining what voltage the laptop is negotiating with the charger? Because based on those specs, it should never try to negotiate the 15 V mode.
Hey @Sean_Greenslade, thanks for checking. It’s just an assumption on my part based on what’s been discussed above and your research with the dev board.
All I know for certain is that the laptop isn’t charging from an Anker device that offers 15V and 20V. But does charge from a smaller charger that offers 5V/9V.
EDIT: Totally could have made incorrect assumptions about the charging device as well.
Thankfully the new charger seems to be working fine. Though, it’s little power indicator tells me it’s charging the laptop at 70+W at times so I’m not sure what that’s about either since it’s supposed to max out at 65W.
Is this 15V charging problem likely to be addressed by a BIOS change or a warranty replacement of the motherboard? I suspect I have the same problem because my dock which delivers 85W power to a Macbook only delivers a tiny amount of power to my Framework.
Seems like the input capacitance (not gate capacitance) is 2094pF which seems somewhat high. Turn on/off delays are also longer.
I guess you don’t really have a choice when the good stuff just isn’t available.
You probably simply need to find good parts with lower capacitance(s) so they won’t have switching problems when the input voltage is around 15V.
Yeah the AON6354 (datasheet) have input capacitance of only 1330pF. Typical, I guess, but the max value shouldn’t be too high either.
I guess you can get them from really anywhere, as long as they meet the specifications.
(browsing Ti.com for 30 minute in search of parts)
I don’t work for Ti. We just have a lot of their stuff floating around. They just look more posh than other stuff, even though the other stuff is still great.
They all look the same, but you only need to add a sprinkle of, say, boron atoms to change the behavior of the (really, transistors) MOSFETs.
These look quite good
Bios update 3.09 mentions completely disabling 15V charging in thr changelog, see BIOS 3.09 Beta release
I have not tried it yet to see if this can still be optionally enabled for boards that have the right transistor, but the changelog wording suggests not.
I added a control register to the PD firmware to enable/disable 15v charging that you could control via EC . I will write up some instructions but since there is only one person who did the rework we don’t plan on officially supporting this.
I just wanted to thank you for following through on this, @Kieran_Levin . I really appreciate it. With the new BIOS / EC firmware, I can indeed use my 18 W power bank to its full capability:
Sure. The computer was at idle, so most of the power was going into the battery. Also, I have a heavy power cap applied to the CPU. Most of the time, the fan is either off or spinning at very low speed. Plus, in my experience, the cooling fan is able to get enough intake air through the second hinge vent to tolerate having the bottom vent blocked.
As to the rework, I personally know several folks who did it here at my office, with the AOS FETs. I also sent a few FETs to colleagues at another office who did a couple. I think the total number was around 4-5 people.
Isn’t this also relevant for people who got a board with the original correct FET, not just those who reworked their board? Or can the BIOS already detect this and keep 15V charging enabled automatically on these boards (the BIOS changelog implies that 14-16V charging is disabled unconditionally).
