The MAXREFDES1044 is a reference design for the MAX30101 and several other Maxim® products that demonstrates how a small size, low cost, low power, high accuracy heart-rate monitor can be easily implemented. This design can monitor heart rate using red, infrared (IR), or green LEDs.
The MAX30101 is an integrated pulse oximetry and heartrate monitor module. It includes internal LEDs, photodetectors, optical elements, and low-noise electronics with ambient light rejection. Other Maxim components used in this design include two MAX8892 (a high PSRR, low-dropout, 150mA linear regulator) to supply 1.8V and 3.3V for the rest of the design and a MAX1555 single-cell lithium-ion (Li+) battery charger to charge a Li+ battery. Two MAX40200 (an ideal diode current-switch) are also included to allow either the battery or VBUS from the USB port to supply power. The MAX40200 ideal diode has a forward voltage drop that is an order of magnitude better than a Schottkey diode. The MAX6864 (a nanopower μP supervisory circuit with manual reset and a watchdog timer) is used to monitor the 3.3V supply voltage and reset the microcontroller if it drops below 3.1V. The design also contains an FTDI FT234 USB-to-serial UART interface and a STMicroelectronics® STM32L432KC low-power microcontroller.
This document describes the hardware shown above. It provides a detailed systematic technical guide to design in a small-size, low-cost, low-power, high-accuracy heart-rate monitor. The design has been built and tested, details of which follow later in this document.