Datasheet

SpO
2
Temperature Compensation
The MAX30101 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 tempera-
ture of the IC. Use Table 13 to estimate the temperature.
Red LED Current Settings vs. LED Tempera-
ture Rise
Add this 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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MAX30101 High-Sensitivity Pulse Oximeter and
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