Are there recommendations for power sequencing, isolation, and temperature management for the MAX30101/2?

It is essential to provide proper power supply sequencing during power up. This is necessary so that current spikes from VLED/PGND do not corrupt the power sequence of the part via VDD and GND. VDD should be supplied before VLED. This is done by making the value of the bypass capacitor for VLED twice that of VDD. Make sure that the LED current does NOT flow into ANY portion of the analog supply loop. This is accomplished using separate LDO supply routing. If this is not done, then high frequency noise can be induced in the analog supply. For temperature, layout is crucial for proper operation and accuracy of the MAX30102. Wavelength of LED light waves is a function of temperature. Therefore, you need to make sure that the temperature of the MAX30102 (specifically pins 8 to 10) are constant in temperature. To reduce self-heating of the integrated LEDs, a relatively large thermal mass should be provided on the PCB to dissipate heat from the MAX30102 via pins 8 to 10. Since this thermal mass can directly induce heat to the MAX30102, make sure it is oriented as far away as possible from any external heat source.

Can 3.3V logic be used for the I2C pins of the MAX30101 even though VDD is 1.8V?

The device I/O can withstand up to 5.5V. The device will function properly when 3.3V is used for the I2C. The only caveat is slightly higher power consumption.

Why is the PPG signal saturated when using the MAX30101, MAX30102, or MAX30105?

The LED current may be set too high. Please try reducing the LED Pulse Amplitude.

Can Maxim provide the MAX30101 LED location and package details?

If a customer would like to alter the LED and/or photodiode locations or angles on the MAX30101 then the MAX86140 or MAX86141 are the recommended devices to use. However, Maxim can provide the package details to customers with the respective Business Manager's approval. If this is something you're interested in please contact a Maxim Support Applications Engineer for further details.

For MAX30101, is it necessary to add extra light barrier between chip glass and phone glass?

There are light barriers in the chip module. From chip glass and phone glass, the airgap should be 0.2mm~0.5mm. Normally, we don't add extra light barriers and don't add ink painting on the phone glass inner side.

Why do the green and red LEDs on the mother board keep flashing, when using the MAX30101ACCEVKIT?

If the MAX30101 is disconnected without first exiting the GUI, the firmware on the microcontroller might get corrupted. In this case the two lights on the microcontroller may keep flashing without stopping. In this scenario, the firmware must be reflashed and tested again using the GUI. The suggested software for this operation is Silicon Labs Flash Programming Utility. It is not provided with the EV kit but can be found on the Silicon Labs website.

How can PPG signal quality be improved when measured on the wrist?

Please note that the MAX30101 PPG module was developed for finger applications and not for the wrist. But to improve measurements for wrist-based heart rate applications try the following optimizations: 1. If haven't done already, please use green LED. This is the recommended LED for wrist application as it is less susceptible to motion artifacts and you will get a cleaner signal compared to red and infrared (IR) LED. 2. Please try increasing the LED current and keep the wrist very still. In general, the wrist has a low blood perfusion index so it's more challenging to get a good signal, and the signal is more susceptible to any motion compared to the finger, for example. 3. Please try increasing the sample average. That will reduce the signal noise.

Can the IR sensor of the MAX30101 be used to measure body temperature?

Answer: No. The photodiode is optimized for the spectrum of the LEDs used. (The IR LED is 880 nm; the red LED is 660 nm.) Measuring body temperature requires a good response to wavelengths more than 10 times longer, which is not feasible using a silicon photodiode. If non-contact temperature measurement is required then a thermopile -based sensor would be better suited.

Why is the MAX30101 green LED not lighting?

The green LED has a higher turn-on voltage than the red and IR LEDs, so we recommend supplying 4.5-5V to VLED if using the green LED. The green LED also tends to work best with higher current than the red or IR.

In PPG monitor, is Yellow LED used and what is the advantage?

Green/Yellow optical sensor array can provide superior measurement with all skin tones. Better than monitors and watches that employ only green sensors.

How can a customer package a MAX30101 to be used underwater?

The MAX30101 itself does not have an ingress protection (IP) rating of its own. It is the customer's final product containing the MAX30101 that is able to obtain an IP rating (if desired). It is left to the customer's system designer to determine how to package the final product for an IP rating of interest. Please go through a third-party for assistance on packaging the the MAX30101 for underwater use.

MAX30101 UV tolerant?

Q: Will there be any degradation of the MAX30101 when it is exposed to UV light, specifically the lens? Will the UV damage the MAX30101 device? A: No, there are no adverse effects to the silicon as a result of moderate UV exposure. Prolonged exposure to UV light can incur aging effects in plastics such as the LED plastic packages and LCP packaging material. Customers that include the MAX30101 in a final assembly that uses UV light to cure composite adhesives of the enclosure should be perfectly fine. Under normal, short duration intense UV light applications (e.g., 60 seconds dental curing used for polarization of light cure composites), there will be no problems to the optical components or the silicon.

How do I read the FIFO of MAX30101?

Max30101 comes with a FIFO that can hold 32 samples of data. There is one set of red, ir, and green data in each sample. Every data sample occupies 3 bytes. Therefore, if we only care to read the RED and IR LED, then after reading all the samples available, 6 bytes need to be extracted from every sample. The first three bytes are for RED ADC data, and the last three bytes are for IR ADC data. Up to 32 sets of sample data can be saved. Old FIFO data needs to be read before FIFO is full. Once it is full, samples are not pushed onto the FIFO, and they are lost.

What Cover Material Can I Use for the MAX30101, MAX30102, or MAX30105?

Any material with high transmission in the visible range can work as a cover material. Specifically, the spectral response has to be 90% or above for the wavelengths of the LEDs. For MAX30101 and MAX30105, the spectral transmittance response has to be 90% or above around 537nm, 880nm and 660nm wavelengths. For MAX30102, the spectral transmittance response has to be 90% or above around 880nm and 660nm wavelengths. Some materials used in the past are Plexiglass 7N and AF32 glass.

Which Maxim Pulse Oximeters integrate Red/IR LEDs?

All Maxim pulse oximeter modules currently integrate the Red/IR LEDs (MAX30101, MAX30102) needed to determine heart rate and SpO2. The MAX30101 also integrates a green LED.

How to select the green LED only on the MAX30101

Multi-LED allows the setting of individual LEDs on the MAX30101 To use only the green LED you can set the mode to Multi-LED by setting MODE[2:0] to 111b (Table 4, page 19) and set the Red LED: LED1_PA[7:0] and IR LED: LED2_PA[7:0] currents to 0. With a green only configuration you will only be able to acquire HR values. The sample rate, pulse width and LED current will also have a considerable impact on power in a wearable application.

How do I set up interrupt for MAX30101/MAX30102 for reading data?

There are two kinds of interrupt sources relevant for reading data from the MAX30101 or MAX30102. The first is A_FULL, which triggers when the 32 samples of FIFO data is about to get full. The number of free samples away from full FIFO can be programmed by setting FIFO_A_FULL[3:0] in the FIFO Configuration register. For example, the interrupt can be triggered when the FIFO is one sample away from being full, or when it is two samples away from being full. The interrupt is cleared by reading the Interrupt Status 1 register (0x00). If A_FULL_EN is set, the master will be informed to read the data via hardware interrupt once the interrupt triggers. Otherwise, the host will have to poll the Interrupt Status 1 register to determine whether the interrupt has occurred. The second is PPG_RDY, which triggers for every new sample of data. The interrupt is cleared by reading the Interrupt Status 1 register (0x00), or by reading the FIFO_DATA register. If PPG_RDY_EN is set, the host processor will be informed to read the data via hardware interrupt once the interrupt triggers. Otherwise, the host will have to poll the Interrupt Status 1 register to determine whether the interrupt has occurred.

How do I set the sample rate for SpO2 measurements in multi-LED mode for the MAX30101?

You do this in the same way as the other modes. This is because in multi-LED mode, a sample consists of three slots, one for each LED. To set the sample rate, the user has to write to the bits [4:2] of the SpO2 Configuration register with address 0x0Ah. Table 6 in the datasheet lists the available samples-per-second configurations.

How do I configure MAX30101 in Multi-LED Mode?

1. Mode Configuration (0x09): please configure the device in Multi-LED mode by setting bit0-2 of Register 0x09 to 0b111. 2. Multi-LED Mode Control Registers (0x11–0x12): Register 0x11 and 0x12 should be configured as necessary for the end application. For example, to turn on IR, red, and green LEDs, three time slots would be needed. In this case, register 0x11 may be set to 0x21, and register 0x12 may be set to 0x03. 3. LED Pulse Amplitude (0x0C–0x10), The next step is to configure register 0x0C - 0x0F for setting the LED current as shown below. If three time slots were used, only 0x0C-0x0E need to be configured. 4. FIFO Data Register FIFO_DATA[7: 0] 0x07： To read collected data, please perform a read of FIFO data register. The number of bytes to read depend on the number of time slots that are enabled. For example, for three time slots (e.g IR, Red, and Green LED), 9 bytes need to be read to get one sample.

How do I convert the "Time" output in the log output by the MAX30101ACCEVKIT into seconds?

The "Time" column represents the number of the sample. Therefore, to convert to seconds, you would multiply the number of the sample times the inverse of the sample rate (in samples per second).