Overview

The MAX30102 is an integrated pulse oximetry and heart-rate monitor IC manufactured by Maxim Integrated (Analog Devices). It combines a 660 nm Red LED, an 880 nm Infrared (IR) LED, photodetectors, optical lenses, ambient light cancellation circuitry, and an 18-bit ADC inside a tiny 5.6×3.3 mm5.6 \times 3.3\text{ mm} package.

It measures blood oxygen saturation (SpO2\text{SpO}_2) and heart rate in Beats Per Minute (BPM) by detecting photoplethysmogram (PPG) optical absorption changes in arterial blood vessels when a finger is placed over the glass cover window.

Quick reference

Breakout Module Supply (VIN)3.3 V to 5.0 V DC (onboard 1.8V & 3.3V LDO regulators)
Chip Power Supply (VDD)1.7 V to 2.0 V DC
LED Driver Voltage (VLED)3.1 V to 5.25 V DC
LED WavelengthsRed: 660 nm / Infrared: 880 nm
ADC Resolution18-bit delta-sigma ADC (up to 3200 samples per second)
Communication InterfaceI2C (fixed slave address 0x57, up to 400 kHz)
FIFO Buffer32-sample internal FIFO buffer
Operating Current600 µA active, 0.7 µA shutdown

Pinout

Standard 5-Pin / 7-Pin Breakout Board Header

PinNameTypeDescription
1VINPower InputSupply voltage (+3.3 V to +5.0 V DC)
2GNDPowerGround (0 V)
3SCLDigital InputI2C Serial Clock input
4SDADigital I/OI2C Serial Data line
5INTDigital OutputActive-LOW Interrupt output (alerts MCU on new sample or FIFO full)
6IRDPower OutputInfrared LED cathode connection (internal connection on 5-pin boards)
7RDPower OutputRed LED cathode connection (internal connection on 5-pin boards)

Specifications

ParameterSymbolMinTypMaxUnitConditions
Chip Voltage (VDDV_{DD})VDDV_{DD}1.71.82.0VDC
LED Voltage (VLEDV_{LED})VLEDV_{LED}3.13.35.25VDC
Peak Current (Red LED)IREDI_{RED}02550mAProgrammable in 0.2mA steps
Peak Current (IR LED)IIRI_{IR}02550mAProgrammable in 0.2mA steps
Sample RateSRSR504003200SPSSamples per second
Dynamic RangeDRDR—89—dBAmbient light cancellation

Photoplethysmography (SpO2\text{SpO}_2) Principle

Oxygenated hemoglobin (HbO2\text{HbO}_2) absorbs more Infrared light (880 nm880\text{ nm}), whereas deoxygenated hemoglobin (Hb\text{Hb}) absorbs more Red light (660 nm660\text{ nm}).

By calculating the ratio of ratios (RR) from the AC and DC components of the Red and IR PPG signals:

R=(ACRed/DCRed)(ACIR/DCIR)R = \frac{(AC_{\text{Red}} / DC_{\text{Red}})}{(AC_{\text{IR}} / DC_{\text{IR}})}

SpO2 (%)=110−25×R\text{SpO}_2\text{ (\%)} = 110 - 25 \times R

Wiring

MAX30102 Breakout Pin→Microcontroller (Arduino Uno / ESP32)
VIN3.3V (or 5V)
GNDGND
SCLSCL (A5 on Uno, GPIO22 on ESP32)
SDASDA (A4 on Uno, GPIO21 on ESP32)
INTGPIO Pin with Interrupt support (e.g. D2 / GPIO4)
Warning

Medical Safety Warning & Cheap Breakout I2C Pull-up Flaw:

  • Hobbyist Non-Medical Device: The MAX30102 is an educational/hobbyist sensor. It must NOT be used for medical diagnosis, patient monitoring, or life safety.
  • Cheap Breakout PCB Flaw: Some low-cost purple/green MAX30102 breakout boards miswire the onboard I2C pull-up resistors to the 1.8V rail instead of 3.3V, causing I2C communication failures on 3.3V/5V MCUs. Cut the 1.8V pull-up trace or add external 4.7 kΩ4.7\text{ k}\Omega pull-up resistors to 3.3V.

Common mistakes

  • Excessive finger pressure: Pressing down hard on the sensor cuts off capillary blood flow in the fingertip, flattening the AC PPG pulse and causing zero readings. Rest the finger gently over the glass window.
  • Ambient Light Leakage: Bright indoor light bleeding into the optical receiver photodiode distorts SpO2\text{SpO}_2 calculations. Cover the finger and sensor with a dark cloth or clip.
  • MAX30100 vs MAX30102 differences: The MAX30100 is an older IC with different register addresses and 14-bit resolution. Software libraries written for MAX30100 will NOT work on MAX30102.

Notes

  • Supported by popular open-source libraries like SparkFun_MAX3010x for automatic heart rate and SpO2\text{SpO}_2 calculation.

Assets & downloads