Medical Pulse Oximeter: ADI OPA dic + ADC Achieve <0.1% SpO2 Error

Challenge

A medical device manufacturer needed Class IIb SpO2 accuracy (<3% ARMS) for their bedside patient monitor while operating on a single 3.3V rail from a Li-ion battery — all within a 35mm × 35mm PCB.

Solution

ADI OPAx392 precision op-amp front-end for photodiode current-to-voltage conversion, followed by AD7175 24-bit Σ-Δ ADC. Both specified at 3.3V single supply with 4kV ESD protection.

Key Outcomes