Datasheet

In the Heart Rate mode, only the Red LED is used to
capture optical data and determine the user’s heart rate
and/or photoplethysmogram (PPG).
SpO
2
Temperature Compensation
The MAX30102 has an accurate on-board temperature
sensor that digitizes the IC’s internal temperature upon
command from the I
2
C master. The temperature has an
effect on the wavelength of the red and IR LEDs. While
the device output data is relatively insensitive to the wave-
length of the IR LED, the red LED’s wavelength is critical
to correct interpretation of the data.
Table 13 shows the correlation of red LED wavelength versus
the temperature of the LED. Since the LED die heats up with
a very short thermal time constant (tens of microseconds),
the LED wavelength should be calculated according to the
current level of the LED and the temperature of the IC. Use
Table 13 to estimate the temperature.
Red LED Current Settings vs.
LED Temperature Rise
Add the temperature rise to the module temperature
reading to estimate the LED temperature and output
wavelength. The LED temperature estimate is valid even
with very short pulse widths, due to the fast thermal time
constant of the LED.
Interrupt Pin Functionality
The active-low interrupt pin pulls low when an interrupt is
triggered. The pin is open-drain, which means it normally
requires a pullup resistor or current source to an external
voltage supply (up to +5V from GND). The interrupt pin is
not designed to sink large currents, so the pullup resistor
value should be large, such as 4.7kΩ.
Table 13. RED LED Current Settings vs. LED Temperature Rise
RED LED CURRENT SETTING
RED LED DUTY CYCLE (% OF LED
PULSE WIDTH TO SAMPLE TIME)
ESTIMATED TEMPERATURE
RISE (ADD TO TEMP SENSOR
MEASUREMENT) (°C)
00000001 (0.2mA) 8 0.1
11111010 (50mA) 8 2
00000001 (0.2mA) 16 0.3
11111010 (50mA) 16 4
00000001 (0.2mA) 32 0.6
11111010 (50mA) 32 8
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Maxim Integrated │ 24
MAX30102 High-Sensitivity Pulse Oximeter and
Heart-Rate Sensor for Wearable Health