Wearable Cardiac & SpO2 Monitor — PCB Design Case Study

A medical startup needed a wearable PCB to capture clinical-grade ECG and SpO2 data continuously for 72 hours on a coin-cell equivalent battery budget. The design had to meet IEC 60601-1 applied-part requirements, pass FCC Part 15 for BLE, and fit a rigid-flex assembly inside a 42 mm wristband housing.

• 4-layer rigid board, 38 mm × 28 mm, 0.8 mm total thickness
• ECG front-end: 24-bit ADC, 0.05–150 Hz bandwidth, CMRR > 80 dB, input-referred noise < 1 µV RMS
• BLE 5.2 antenna: 50 Ω trace matched to chip antenna, clearance from copper per antenna vendor keep-out
• IEC 60601-1 patient isolation — 1500 V reinforced isolation between applied-part and system power
• Power budget: 72-hour runtime from 200 mAh LiPo — average draw < 2.7 mA
• All components 0201 or smaller; 0.35 mm pitch BGA for IMU

• Separated analog and digital ground planes with a single star-point junction at the ADC reference pin, eliminating digital noise coupling into the ECG front-end
• Achieved IEC 60601-1 1500 V isolation using a 8 mm creepage gap routed as a slot through all copper layers, passing Hi-Pot test at 1800 V
• BLE antenna tuning required removing copper from 3 layers beneath the antenna zone — redesigned component placement to preserve this clearance without violating the form factor
• Achieved 2.4 mA average draw by mapping MCU sleep states to ECG sampling windows; SpO2 LED duty cycle reduced to 1% with oversampling compensation

• Full schematic (88 references) with analog isolation domain clearly demarcated
• 4-layer PCB layout with IPC-2221 annotation for medical creepage/clearance
• BOM with approved medical-grade component alternates
• IEC 60601-1 isolation gap documentation for regulatory submission
• Gerber, ODB++, and Pick-and-Place files for SMT assembly
• DFM sign-off from two medical EMS partners

Prototype passed IEC 60601-1 Hi-Pot and patient leakage current tests at a certified lab on first attempt. 72-hour runtime validated on bench. Client submitted 510(k) pre-submission with the design documentation package.