ESP32 PPG Sensor Design

flux

0:08

Work done
  • Separated the charger programming path from output channel 1 by moving MCP73871 PROG1 onto dedicated resistor R8, while keeping channel output on R4.
  • Added optional USB-C power input using J2 with 5.1 kOhm CC pull-downs R6 and R7, plus input capacitors C11 and C12, and tied VIN_5V into charger U3.
  • Tied unused MCP73871 status/config pins on U3 to GND so they are no longer floating.
  • Cleaned net intent by creating output-side naming for channel 2 and preserving separate OUT1 and OUT2 current-limit paths through R4 and R5.
  • Defined the layout as an 80 mm x 80 mm rounded rectangle, set Standard 4 Layer stackup, and established baseline layout constraints including 0.15 mm minimum trace width, 0.2 mm keep out, 0.5 mm board inset margin, and preferred widths of 0.15 mm / 0.25 mm / 0.5 mm.
  • Applied explicit net trace-width rules for R8's PROG1 net and the OUT2 GPIO-side net.
Success criteria review
  • ✅ The charger programming resistor is now functionally separated from output channel 1.
  • ✅ The optional USB input/charge connector is added and integrated into the charging path.
  • ✅ The PCB layout now has a compact board size, 4-layer stackup, and baseline manufacturability constraints.
  • ✅ The charger-related ERC issues were reduced by grounding unused MCP73871 pins.
  • ✅ Remaining floating-pin ERC items are now limited to intentionally unused ESP32 module pins, unused USB-C data/SBU pins, unused TVS array I/O pins, and extra standalone GND symbols that were added earlier but are not needed for function.
Next steps The remaining ERC items are cleanup-level and not charger/function blockers. The main follow-up is to remove the unused standalone GND symbols, replace or rewire D1 to a simpler VBUS TVS part, and decide whether the unused ESP32 and USB data pins should stay intentionally unconnected or be terminated/documented. I can do that cleanup pass next.
Fix remaining ERCs
Set compact board size
Add USB charge input
31 days
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ESP32 PPG Battery Device thumbnail
Battery-powered ESP32-WROOM-32 design with MAX30102 PPG sensor, MCP73871 single-cell Li-ion charging and power-path management, 3.3V regulation, and two low-current output terminals.

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