Objective
BioNode is a wrist worn health monitoring device and autonomous emergency beacon designed for users operating in environments where cellular infrastructure is unavailable or unreliable. Built around the nRF54L10 MCU on an 8-layer main PCB, the device continuously acquires multi-modal physiological data - ECG, EMG, EDA, and PPG via a dedicated 6-layer sensor PCB with analog front ends powered by the ADS1292, MAX86141 and AD5940, delivering real-time insight into cardiac activity, muscle response, electrodermal activity, and blood oxygen saturation. On-device anomaly detection processes this data locally, and without any user input, transmits a GNSS-tagged distress alert over Satellite LoRa - no cellular coverage required.
Analog & Mixed-Signal Front End
ECG/EMG: TI ADS1292: 24-bit delta-sigma biopotential AFE, 2-channel, bottom-layer exposed ENIG dry electrodes.
PPG/SpO₂/HR: Maxim MAX86141 optical AFE.
EDA/GSR: Analog Devices AD5940 bioimpedance AFE, bipolar 2-electrode.
Electrode sharing: EDA/EMG share electrodes via a low-leakage precision analog mux (MUX509), two-state (on-demand ECG/EMG vs. background EDA).
Temperature: TMP117 with a dedicated skin-side thermal path.
Motion: LSM6DSV16X 6-axis IMU for motion-artifact cancellation and physical-state classification.
RF & Connectivity
Three co-located radios for an autonomous emergency beacon that transmits location with no cellular coverage.
BLE: nRF54L10 (also host MCU), GNSS: u-blox MAX-M10S (L1) and LoRa: Semtech LR1121 (dual-band sub-GHz + S-band direct-to-satellite).
Per-antenna front ends: SAW BPF + LC matching; All RFIC uses TCXO / OCXO.
Interference Handling: per-band SAW filtering, corner antenna placement, single-radio-active-at-a-time state machine.
Filtering
High-CMRR biopotential AFE (100 dB+).
Hardware input LPF: 19.74 kHz common-mode / 9.87 kHz differential on ECG electrodes.
Digital 60 Hz notch + digital 40 Hz LPF on the ECG channel.
Active RLD + low PGA to reject dry-electrode DC offset and common-mode noise.
Multi-stage ESD/defibrillation protection on all electrode inputs (IEC 60601-2-27)
Power Management
Maxim MAX77654 wearable SIMO PMIC - 1S LiPo charger, 2 buck + 1 boost + 1 ultra-low-noise LDO.
Buck→LDO cascade for the low-noise biopotential rail; dedicated precision reference for the ADS1292.
Separate TPS61040 boost for the PMOLED; BQ27426 fuel gauge; 4-pin magnetic pogo-pin charging; 2.8 V UVLO.
Architecture & Interfaces
Two-board stack: 6-layer analog sensor + 8-layer HDI digital/RF main, mezzanine-connected to isolate the biopotential front end from radios and power converters.
QSPI NOR flash (512 Mbit) logging; 1.3" COG PMOLED (SH1107).
UART console on charging pogo-pins; SWD test points; BLE OTA.
PCB Design
30 × 30 mm high-density boards: 6-layer sensor, 8-layer HDI main.
Fine-pitch BGA / LGA / QFN packages and 0201 passives.
Stackup target: ≥2 internal GND planes, GND pours on remaining layers, 1 power plane, 3 signal layers.
ECG Front End
PPG Front End
PMIC
PMOLED
IMU
Fuel Gauge
