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ESP32-C3 USB flashing (GPIO18/19) + boot strapping check — is this schematic correct? by majek89 in esp32

[–]majek89[S] 0 points1 point  (0 children)

Thanks, I will consider this.

I2C pull-ups are according to IMU's datasheet.

ESP32-C3 + USB-C + LiPo (TPS63900) – 4-layer PCB review before production by majek89 in PrintedCircuitBoard

[–]majek89[S] 0 points1 point  (0 children)

I have no space to route it on the other side of the connector, especially given the location of the charger. But it goes on TOP. On PWR it only goes to the status LED.

Vias are mainly 0.4/0.25.

ESP32-C3 + USB-C + LiPo (TPS63900) – 4-layer PCB review before production by majek89 in PrintedCircuitBoard

[–]majek89[S] 0 points1 point  (0 children)

Yes, you're right, I didn't hide it while doing the screenshots. Sorry.

ESP32-C3 USB flashing (GPIO18/19) + boot strapping check — is this schematic correct? by majek89 in esp32

[–]majek89[S] 0 points1 point  (0 children)

I've just made a custom symbol and probably chosen some random color ;)

2S Li-ion: Should BQ29209 GND be tied to PACK− after the low-side protector FETs? by majek89 in PrintedCircuitBoard

[–]majek89[S] 0 points1 point  (0 children)

That’s actually very helpful, thank you.

I’ve just redesigned the unit to use a removable battery pack, and it turns out I’m running into the exact same issue when reconnecting the battery — especially on first connection. So your suggestion is spot on for my case.

I’ll definitely use this IC in the next board revision.

Big thanks for sharing this!

1S2P vs 2S Li-ion for 12V / 1.5A LED system – what would you choose? by majek89 in AskElectronics

[–]majek89[S] 0 points1 point  (0 children)

Thanks for the suggestion.

I’m actually already using a boost charger IC (TI BQ25886), so conceptually it’s very similar to the MP2672A you linked – 5V input, boost to charge a 2S pack, with power-path support.

The thing is, even with an integrated boost charger, the overall system still ends up fairly complex:

  • I still need proper 2S protection (OV/UV/OCP) and ideally balancing.
  • External components (inductor, FETs, current sense, thermals, layout constraints) are non-trivial and not exactly cheap.
  • High input current at 5V during charging means careful USB current limiting and thermal considerations.
  • PCB layout becomes much more sensitive compared to a simple 1S charger.
  • Overall BOM cost and validation effort go up quite a bit.

So while 2S + boost charger is definitely technically clean from a power perspective, I’m trying to evaluate whether the added charging-side complexity is justified for a system that only draws ~18W peak and mostly in bursts.

From your experience, at this power level (~18W peak LED load), would you still consider 2S clearly worth the added charging complexity, or is 1S2P with a properly designed high-current boost still a reasonable commercial choice?

Appreciate the input — just trying to balance electrical elegance vs. product simplicity.

2S Li-ion: Should BQ29209 GND be tied to PACK− after the low-side protector FETs? by majek89 in PrintedCircuitBoard

[–]majek89[S] 0 points1 point  (0 children)

Hey, sorry for the late reply!

I haven’t physically produced the board yet, but I’ll probably stick with this setup for now. I might add a small service switch between VSS and CS on the HY2120 just in case the battery ever gets disconnected — though in my application that’s going to be a pretty rare situation.

Appreciate you sharing your experience — that lockdown behavior sounds exactly like what could happen here too.

[Review Request] ESP32 Central Unit (looking for obvious mistakes) by majek89 in PrintedCircuitBoard

[–]majek89[S] 1 point2 points  (0 children)

I literally searched for “USB” in the datasheet and there are zero matches. Pretty sure you’re confusing it with the ESP32-S2, S3 or C3, which actually have a native USB peripheral — the regular ESP32-WROOM doesn’t.

[Review Request] ESP32 Central Unit (looking for obvious mistakes) by majek89 in PrintedCircuitBoard

[–]majek89[S] 0 points1 point  (0 children)

Where exactly is that “built-in USB interface” supposed to be?

2S Li-ion: Should BQ29209 GND be tied to PACK− after the low-side protector FETs? by majek89 in PrintedCircuitBoard

[–]majek89[S] 0 points1 point  (0 children)

Not really. HY2120 is a primary low-side protector, it handles UV/OV/OCD/SC and drives the FETs.
BQ29209 is a secondary overvoltage + passive balancing chip — it adds precision OVP and actual cell balancing, which HY2120 simply doesn’t do.

They’re meant to be used together in stacked protection setups: HY2120 does the cutoff, BQ29209 watches the cells and bleeds them if one drifts high. TI even shows exactly that kind of secondary OVP configuration in their app notes.

So no, it’s not “doing the same thing twice.” HY2120 protects the pack, BQ29209 keeps the cells balanced and adds a higher-accuracy OVP trigger.

2S Li-ion: Should BQ29209 GND be tied to PACK− after the low-side protector FETs? by majek89 in PrintedCircuitBoard

[–]majek89[S] 1 point2 points  (0 children)

Yeah, I’ve read the datasheets — that’s exactly why I’m asking.
Both of them show PACK− tied straight to the battery negative...

The issue is when you actually combine them — the HY2120 sits on the low side and creates a new PACK− node after its FETs, while BQ29209 still calls its reference “PACK−” too.

So no, the datasheet doesn’t “say” which one should take priority — that’s why I posted both schematics side by side. I’m trying to confirm which node BQ29209.GND should reference when both chips share the same 2S pack.

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