• Intended as a biomedical-grade development architecture, not a released diagnostic design.
• Worn on skin as a flexible patch with embedded electrodes and microfluidic/electrochemical interfaces.
• Battery-powered during sensing. USB-C is for charging/programming and must trigger patient-signal disable/disconnect.
• Clinical claims for diagnostic ECG, blood glucose, lactate, SpO2, or blood pressure require later safety, regulatory, and clinical validation.

• Acquire ECG biopotential signals for heart-rate/rhythm research.
• Acquire optical PPG for heart-rate/contact-quality research.
• Acquire electrochemical lactate and glucose electrode signals through AD5940-class potentiostat/electrochemical AFE circuitry.
• Monitor contact/pressure using a 0–300 mmHg / 40 kPa digital gauge pressure sensor.
• Track motion for artifact rejection.
• Report data over BLE using an nRF52840 module.
• Monitor battery state of charge and support USB-C LiPo charging.
• Prevent patient-applied sensing from remaining active while USB is attached.

• BLE wireless MCU: Raytac MDBT50Q-1MV2 / nRF52840 module.
• USB-C sink charging input.
• BQ24074 power-path LiPo charger.
• TPS63031 3.3 V buck-boost rail.
• LDK130 adjustable 1.8 V rail for MAX30102 core supply.
• ADS1292R ECG/biopotential AFE.
• MAX30102 PPG sensor.
• AD5940 electrochemical AFE.
• Honeywell MPRLS0300YG00001B pressure/contact sensor.
• KX022-1020 accelerometer.
• MAX17048 fuel gauge.
• FPC connectors for ECG and electrochemical electrode tails.

Diagram

• USB-C sink input with CC pull-downs and VBUS ESD clamp.
• BQ24074 charger / power-path management.
• Protected LiPo pack required; NTC/thermal behavior must be finalized.
• TPS63031 buck-boost generates VSYS_3V3 from LiPo/SYS input.
• LDK130 generates VDD_1V8 for MAX30102 VDD.

• MDBT50Q-1MV2 nRF52840 module provides BLE telemetry, I2C/SPI master, SWD debug, USB device pins, and reset/user controls.
• Antenna must be placed at the flex/rigid edge with module-specific copper keepout.

• ADS1292R connected over SPI.
• ECG electrode inputs route through current-limiting resistors, ESD array, and analog switch disconnect.
• RLD output is included but requires final patient-disconnect/fault review.

• MAX30102 on I2C with 1.8 V core and 3.3 V LED supply.
• Requires optomechanical baffle, opaque window/adhesive stack, and pressure/motion compensation.

• AD5940 connected over SPI.
• Lactate and glucose electrode nets are provisionally routed through FPC connector pins and protection/switching.
• Chemistry, reference electrode, microfluidics, and calibration are not solved by the PCB alone.

• Honeywell MPRLS0300YG00001B pressure sensor on I2C.
• Use as contact/pressure signal or research pulse waveform input. Do not claim cuffless blood pressure without clinical validation.

• USB-C: VBUS, GND, CC1/CC2, D+/D−.
• Battery: 2-pin JST PH LiPo connector.
• SWD: 10-pin 1.27 mm Cortex/SWD header.
• FPC J3: ECG electrode tail; active pins: ECG_RA_RAW, ECG_LA_RAW, ECG_RLD_RAW.
• FPC J4: microfluidic/electrochemical electrode tail; active pins: LAC_WE/RE/CE and GLU_WE/RE/CE.
• I2C: PPG, pressure, accelerometer, fuel gauge.
• SPI: ADS1292R and AD5940.

• Initial current budget is provisional: sleep <1 mA target, active sensing tens of mA, PPG LED pulse peaks can push system peak toward ~150 mA.
• USB input current should initially be limited around 500 mA or less.
• Charge current should be conservative for skin-contact thermal safety, likely ~100 mA until battery capacity and thermal model are defined.
• Runtime depends on cell capacity, BLE duty cycle, PPG LED current/duty, electrochemical sample rate, and ECG sample rate.

• Rigid-flex or flex-with-rigid-islands architecture is strongly preferred.
• Use components on rigid islands; keep bend zones free of components/vias.
• 4-layer stackup is recommended for controlled return paths, RF, USB, and analog partitioning.
• Medical-grade biocompatible adhesive/electrode/encapsulant stack is not yet specified.

• SWD programming/debug through J5.
• BLE telemetry using nRF52840.
• Sensor buses: I2C_SCL/SDA and SPI_SCLK/MOSI/MISO.
• Patient-switch control: PATIENT_SW_CTRL.
• USB attach/safety state available via USB_VBUS and charger status signals.
• Interrupts: PPG_INT_N, ECG_DRDY_N, PRESS_EOC, ACCEL_INT1, FUEL_ALRT_N.

• Flexible rounded patch form matching reference image.
• Approximate first-pass board outline: wide rounded transparent/flex patch with left/right upper microfluidic/electrode regions, central rigid electronics island, bottom electrode/contact area, and edge USB/battery/debug access.
• Antenna on a clean outer edge, not under battery/electrodes/copper.
• Electrochemical and ECG high-impedance traces short, guarded, and far from USB/power/RF.

• Use nRF52840 module rather than bare RF SoC to reduce RF certification and antenna risk.
• Use BQ24074 power-path charger instead of charger-only MCP73831 because sensing system may need controlled SYS power and charge management.
• Use ADS1292R over AD8232 for digital ECG acquisition.
• Use AD5940 for flexible electrochemical research capability.
• Treat pressure sensor as contact/pressure input, not validated blood-pressure measurement.
• Sensing while USB is attached is a safety risk; hardware disconnect and firmware lockout are required.

• Single-cell protected LiPo pack.
• Battery-only sensing during skin contact.
• USB-C is not connected while active patient-applied sensing is enabled.
• Device is development/medical design-intent, not yet certified.
• Sweat/ISF lactate and glucose chemistry will be supplied/validated separately.

• Initial architecture, schematic, and layout concept created from the supplied prototype patch image.
• Added biomedical safety constraints from independent review: patient leakage, hardware disconnect, conservative charging, regulatory documentation, and claim limitations.