Optical blood-pressure trending reference design enables convenient monitoring

Until now, accurate blood-pressure monitoring could only be achieved with bulky and mechanical cuff-based medical devices. Now, Maxim Integrated Products, Inc. has introduced a solid-state blood-pressure monitoring solution to more conveniently track this critical health indicator. Design engineers can develop blood-pressure trending solutions with the MAXREFDES220# reference design from Maxim.

Comprised of a complete integrated optical sensor module, a microcontroller sensor hub and a sensing algorithm, the MAXREFDES220# optical blood-pressure trending solution can be embedded into smartphones or wearables. It enables users to place their finger on a device for 30-45 seconds while resting to measure blood pressure anywhere and anytime. The reference design includes the MAX30101 or MAX30102 high-sensitivity optical sensor, as well as the MAX32664D sensor hub IC with built-in algorithms.

The MAX30101 (using two LEDs) and MAX30102 (using three LEDs) pulse-oximeter and heart-rate optical sensor modules combine photodetectors, LEDs and analog front-end (AFE) electronics with an integrated cover glass. This integrated optical design and lenses-on-top approach enables optimal signal-to-noise ratio (SNR) for a small, lower cost and power-efficient module. It comes in a tiny 5.6mm x 3.3mm 14-pin optical package with an I²C interface to the sensor hub IC.

The MAX32664D sensor hub IC includes firmware which controls the sensor and executes the algorithms which measure cuffless blood pressure, heart rate and blood-oxygen levels. Its ultra-small size (1.6mm x 1.6mm) can easily fit into small devices to seamlessly and effortlessly connect to a device’s host microcontroller.

The MAXREFDES220# provides industry-best accuracy that meets Class-II regulatory limits. For example, under resting-only measurement conditions, the solution provides the following accuracies:

• Systolic Error: Mean = 1.7mmHg, Std Dev = 7.4mmHg
• Diastolic Error: Mean = 0.1mmHg, Std Dev = 7.6mmHg
• For reference, Class-II regulatory limits are |Mean Error| ≤ 5mmHg, and Std Dev ≤ 8mmHg

This solution requires calibration every four weeks to maintain above accuracies. This is based on independent testing and a limited number of subjects at resting condition. 

MAXREFDES220# reference design is available at Maxim’s website for $100; also available from authorized distributors

• MAX32664D in WLP package is available at Maxim’s website for $63 (1000-up, FOB USA); select variants available from authorized distributors
• MAX30101 is available at Maxim’s website for $4.23 (1000-up, FOB USA); also available from authorized distributors
• MAX30102 is available at Maxim’s website for $4.13 (1000-up, FOB USA); also available from authorized distributors