Optical Biometric Sensor Hub Algorithms

Sensor Hubs Help Collect and Process Raw Biometric Data

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

Optical Biometric Sensor Hub Selector Table

MAX32664 Data Sheet

MAX32664
Sensor Hub Version
Optical Sensor IC Data Measurement Type Body Location Part Numbers Reference Design
MAX32664A MAX30101
MAX30102
SpO2
Pulse HR
Finger MAX32664GTGA+ (TQFN, Bulk)
MAX32664GTGA+T (TQFN, T&R)
MAX32664GWEA+ (WLP, Bulk)
MAX32664GWEA+T (WLP, T&R)
MAXREFDES220
MAX32664B MAX86140
MAX86141
Pulse HR Wrist MAX32664GWEB+ (WLP, Bulk)
MAX32664GWEB+T (WLP, T&R)
MAXREFDES101
MAX32664C MAX86140
MAX86141
SpO2
Pulse HR
Wrist MAX32664GWEC+ (WLP, Bulk)
MAX32664GWEC+T (WLP, T&R)
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MAX32664D MAX30101
MAX30102
SpO2
Pulse HR
BP Trending
Finger MAX32664GWED+ (WLP, Bulk)
MAX32664GWED+T (WLP, T&R)
MAXREFDES220
MAX32664Z - Evaluates All - MAX32664GWEZ+ (WLP,Bulk) -

SpO2 = Pulse Blood Oxygen Saturation, HR = Heart Rate, BP = Blood Pressure

The following sections provide a brief description of each of the four versions of the MAX32664 Biometric Sensor Hub.

MAX32664A


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.

MAX32664A: Supports SpO2 Measurement Enlarge+



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For this variant, reference the following part numbers:

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

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MAX32664B


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.

MAX32664B: Supports Heart-Rate Measurement Enlarge+



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For this variant, reference the following part numbers:

  • MAX32664GWEB+
  • MAX32664GWEB+T

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MAX32664C


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.

MAX32664C: Supports Heart Rate and SpO2 Measurement Enlarge+



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For this variant, reference the following part numbers:

  • MAX32664GWEC+
  • MAX32664GWEC+T

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MAX32664D


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.

MAX332664D: Supports Blood Pressure, SpO2, and Heart-Rate Measurement Enlarge+



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For this variant, reference the following part numbers:

  • MAX32664GWED+
  • MAX32664GWED+T

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MAX32664Z


Some users may wish to experiment with several versions of the MAX32664 in different applications. Since each version of the MAX32664 will only load an algorithm encrypted with its corresponding encryption key (for example, MAX32664A will only load an algorithm encrypted with the ‘A’ encryption key) we have developed an evaluation version to simplify development: the MAX32664Z. This single IC contains only a bootloader and a ‘Z’ encryption key which allows algorithms for any of the MAX32664 variants to be loaded (not simultaneously). This requires a special version of each algorithm (MAX32664A, B, C, or D algorithms with a ‘Z’ encryption key). In this way the MAX32664Z can be configured to function as any of the A/B/C/D versions. The version being evaluated will determine which sensor interface must be used (either SPI or I2C) as shown in the table above. MAX32664Z is not available for mass production and is intended only for use in algorithm evaluation and selection. To download the Z algorithms, go to the Design Resources tab and download the software package for the variant you would like to evaluate.

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