Optical Biometric Sensor Hub Algorithms

MAX32664 is a family of four biometric sensor hubs (versions A, B, C, D) each with embedded firmware and algorithms, specifically developed for use in health and fitness wearables. The MAX32664 family can communicate with several of Maxim’s optical sensor solutions (see table for details) delivering raw or calculated data, as required by the user application. This is achieved while also minimizing overall system power consumption. All versions interface to a host microcontroller through a fast-mode, slave I²C interface, providing access to raw or processed sensor data. Future updates to the firmware and algorithms will be made available to download. These can then be uploaded to the MAX32664 through its I²C interface.

Benefits of using a Biometric Sensor Hub:

• Enables new wearable health monitoring use cases for home-based care solutions, including
  • wrist worn blood-pressure monitoring
  • wrist worn SpO₂ monitoring (to assist in the detection of sleep apnea)
• An “all-in-one” bundled solution reduces time to market.
• Fully tested and validated solution allows you to effortlessly incorporate accurate biosensing features into your wearable designs
• Meets the size, power, and accuracy requirements of wearable healthcare products

MAX32664A enables users to capture raw and calculated SpO₂ and heart-rate data through in finger-based applications. The part is preprogrammed with the firmware, drivers, and algorithm that are required to interface with the MAX30101 sensor device through an I²C port. The I²C slave interface is also used for establishing communication with a host microcontroller (e.g., MAX32630) as shown in the figure. The MAXREFDES220# reference design, which includes the MAX30101 and the MAX32664, provides an integrated hardware and software solution for finger-based applications.

The embedded algorithm uses digital filtering, pressure/position compensation, advanced R-wave detection, and automatic gain control to determine the heart rate in beats per minute while minimizing power. Also, the Maxim Integrated sensor hardware has built-in ambient light rejection to minimize background noise. SpO₂ results are reported as percentage of hemoglobin that is saturated with oxygen. The calibration values for SpO₂ configuration should be determined while using the end-product.

Design Resources

• Download software ›
• "Guidelines for SpO₂ Measurement Using the Maxim MAX32664 Sensor Hub"
  
• "MAX32664 User Guide"

Order Now ›

For this variant, reference the following part numbers:

• MAX32664GTGA+
• MAX32664GTGA+T
• MAX32664GWEA+
• MAX32664GWEA+T

MAX32664 version B is specifically targeted for the measurement of heart rate in wrist-worn applications. Combined with the MAX86141 optical sensor and a 3-axis accelerometer, it provides a sensor’s raw data, as well as calculated heart-rate data, to a host device through its I²C slave interface. The MAX32664B interfaces to the MAX86141 optical sensor through the SPI bus. An accelerometer is mandatory for heart-rate monitoring. A KX122 accelerometer can be connected directly to the MAX32664B. Alternatively, an external 3-axis host-side accelerometer can be used. In this case, the host needs to periodically provide accelerometer readings to the sensor hub. The MAXREFDES101# reference design, which includes both the MAX86141 and the MAX32664, provides an integrated hardware and software solution for evaluating heart rate measurements in wrist-worn solutions.

The embedded algorithm uses digital filtering, distance/motion compensation, and advanced R-wave detection to determine the pulse rate in beats per minute. Power usage is minimized with automatic power-minimized gain control. In addition, the Maxim Integrated sensor hardware provides additional features such as ambient light rejection, higher signal-to-noise (SNR) ratio, and external LEDs for optimal placement.

Design Resources

• Download software ›
• "MAX32664 User Guide"

Order Now ›

For this variant, reference the following part numbers:

• MAX32664GWEB+
• MAX32664GWEB+T

MAX32664C enables users to capture raw, as well as calculated Pulse Blood Oxygen Saturation (SpO₂) and heart-rate data, in wrist worn applications. The part is preprogrammed with the firmware, drivers, and algorithm that are required to interface with the MAX86141 sensor device through the SPI port. The I²C slave interface is dedicated to establishing communication with a host microcontroller. In order to properly capture and calculate the data, this solution requires an accelerometer. The MAX32664C firmware includes the required drivers for the Kionix^® KX122 accelerometer, which is wired together with the MAX86141 to the same SPI port. Alternatively, a host-side accelerometer can be used. In this case, the sampled accelerometer data is required to be periodically reported to the MAX32664C by the host microcontroller.

The embedded algorithm uses digital filtering, distance/motion compensation, and advanced R-wave detection to determine the pulse rate in beats per minute. Power usage is minimized with automatic power-minimized gain control. SpO₂ results are reported as a percentage of hemoglobin that is saturated with oxygen. The calibration values for SpO₂ configuration should be determined while using the end product. In addition, the Maxim Integrated sensor hardware provides additional features such as ambient light rejection, higher signal-to-noise (SNR) ratio, and external LEDs for optimal placement.

Design Resources

• Download software ›
• "Guidelines for the Opto-Mechanical Integration of Heart-Rate Monitors in Wearable Earbud Devices"
  
• "Guidelines for the Opto-Mechanical Integration of Heart-Rate Monitors in Wearable Wrist Devices"
  
• "Guidelines for SpO₂ Measurement Using the Maxim MAX32664 Sensor Hub"
  
• "MAX32664 User Guide"

Order Now ›

For this variant, reference the following part numbers:

• MAX32664GWEC+
• MAX32664GWEC+T

MAX32664D enables users to capture raw and/or calculated systolic and diastolic blood pressure (BP), SpO₂, and heart-rate data in finger-based applications. The part is preprogrammed with the firmware, drivers, and algorithm that are required to interface with the MAX30101 sensor device through an I²C port. The I²C slave interface is also used for establishing communication with a host microcontroller. The MAXREFDES220# reference design provides an integrated hardware and software solution for evaluation of blood pressure measurements (in addition to heart rate and SpO₂ measurement referred to previously for MAX32664A).

The embedded algorithm uses digital filtering, pressure/position compensation, advanced R-wave detection, and automatic gain control to determine the heart rate in beats per minute while minimizing power. Also, the Maxim Integrated sensor hardware has built-in ambient light rejection to minimize background noise. SpO₂ results are reported as percentage of hemoglobin that is saturated with oxygen. The calibration values for SpO₂ configuration should be determined while using the end-product. Blood pressure is reported for systolic and diastolic blood pressure. Blood pressure cuff measurements are used to set the blood pressure calibration data in the firmware.

Design Resources

• Download software ›
• "Guidelines for SpO₂ Measurement Using the Maxim MAX32664 Sensor Hub"
• "MAX32664 User Guide"

Order Now ›

For this variant, reference the following part numbers:

• MAX32664GWED+
• MAX32664GWED+T