I was having problems with the 3.3V power rail (VCC pin) on the MKR Vidor 4000 not coming up if I put a large design in the FPGA. This can also be reproduced by putting a resistive load between VCC and GND (I used 18.5 Ohms for a 180mA load, and the 3.3V rail only got up to 2.1V). The EZ6301QI that generates the 3.3V rail should be able to generate up to 1.5A.
It turns out that this is due to the BQ24195L battery-charging IC limiting the current drawn from the USB power source to 100mA, so VSYS was around 2.1V. This IC is designed to detect the type of USB power source connected and limit the current draw appropriatetely.
So why did the BQ24195L fail to detect that I had connected a Dedicated Charging Port, and increase the current limit to 1.5A? Well on the Vidor 4000 modules I have here, R59 and R60 are not connected, so the BQ24195L has no connection to the USB port data lines and cannot detect the charger type!
I cannot see how this could ever work with a design that needs more than 100mA from the power source. Was there a build fault on the boards I received? It would help if the schematics indicated which components are meant to be fitted.
(Even if these resistors were fitted, the BQ24195L would limit the current to 100mA when power is supplied through the VIN pin instead of the USB port.)
Am I missing something?
Interesting, all my boards are missing R59 and R60 too, so it's not a random build fault. There had to be some consideration behind this choice.
I posted this question with lots of technical detail in hopes of getting some support from the designers/manufacturers, but it looks like they stopped providing support about 2 years ago. I'll repost it in the form of a warning to others that may see this issue.
Good that I noticed this.
I'm doing carrier board for this as hobby and was planning to order soon.
Had to check my schematics. I have "hot" running component there, maybe I just replace LT1117-3.3 with SMPS circuit.
See the thread Power-up issues in MKR Vidor 4000: how to recognise, how to fix for further discussion of this issue.
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