Can the luminous intensity of the MAX30101 LED be independently adjusted?

The current of the LED can be adjusted; the maximum is 50mA. In addition, the pulse width of the current can also be adjusted. The range of adjustment covers 4 stages. Every LED light signal can be adjusted independently.

Does the MAX30101 requires temperature compensation?

Although Maxim designs parts with an eye toward future needs, most of MAX30101 customers SPO2 accuracy specification was +/- 2~3% of SPO2 level. And the compensation by temperature was very small compared to wide specification when SPO2 level is greater than 90%. So, currently Maxim does not provide any customer with compensation procedures using temperature data for SPO2.

Are larger currents better for the MAX30101 luminous tube?

Considering power consumption and effective resolution, it is not better to have a larger current. However, for some parts to be measured (such as a wrist), or objects to be measured (such as people with darker skin color and people who are physically overweight), the current of the luminous tube needs to be increase to effectively obtain the strength of the available signal and obtain the measured value.

Why does quality of the HR and SpO2 reading from the MAX30101 decrease when my finger is cold?

This result is expected. This is not because of the MAX30101/2, but rather because of the PPG signal itself. Colder temperatures reduce blood flow, which results in a reduced PPG signal quality. This affects our algorithm’s ability to detect heart rate and SpO2. I would recommend looking at this research paper if you would like to learn more about this topic: https://www.sciencedirect.com/science/article/pii/S2405896315020571

Is there any wake up delay after toggling the SHDN bit in the MAX30101?

SHDN just disables the sampling part of the chip but doesn’t actually power down any of the critical parts of the chip, so there is no wake-up delay. There is only a delay if the part is RESET or power cycled.

What is the order of sample data output from the MAX30101?

In multi-LED mode the order of the samples output by the MAX30101/2 is chronological with the order of time SLOTS for the LEDs that are enabled. i.e with SLOT1 enabled as LED1 (RED) and SLOT2 enabled as LED2 (IR), the samples output will be 3 bytes of red LED and 3 bytes of IR LED in that order and then revert back to the red LED to start again. Note: The slots should be enabled in order (i.e., SLOT1 should not be disabled if SLOT2 or SLOT3 are enabled).

How can we stop the MAX30101 from collecting data without disrupting the communication or resetting the registers?

The SHDN bit can be toggled to stop the part from collecting data without disrupting the communication or resetting any registers

What is the saturation value of the MAX30101 OVF_COUNTER register?

When the MAX30101 FIFO is full, the number of samples "missed" are counted by this 5-bit register. The OVF_COUNTER register, since it is 5 bits, has a maximum value of 0x1F and will saturate at this value if the number of missed samples exceeds 0x1F.

The measured waveforms from the MAX30101 and MAX30102 do not match the standard waveforms on the web. Why is this?

This is because there are two types of PPG heart-rate sensor and oximeter solutions: transmission mode and reflection mode. The waveforms for the two modes are different. Our MAX30101/2 works based on the reflection mode. Therefore, the waveforms may be different from the ones that were found on the web.

Is there a way to change the I2C address of the MAX30101 or MAX30102?

Unfortunately there is no way to change the default I2C address of the MAX30101/2. If you require more LED's on the same bus consider using the MAX86140/1 AFE which feature an SPI interface and allow for a number of different configurations for arrays of LEDs as detailed in the datasheets.

What value does the MAX30101 FIFO_A_FULL register represent?

The value programmed into the FIFO_A_FULL represents the number of empty spaces left in the FIFO when the A_FULL interrupt will be triggered. See the table below for clarification. Bits 3:0: FIFO Almost Full Value (FIFO_A_FULL) This register sets the trigger for the FIFO_A_FULL interrupt. For example, if set to 0x0F, the interrupt triggers when there are 15 empty spaces left (17 data samples), and so on. FIFO_A_FULL[3:0] NO. OF SAMPLES IN THE FIFO 0x00h 32 0x01h 31 0x02h 30 0x03h 29 .. .. 0x0Fh 17

Can the MAX30101/MAX30102 detect when the medical device is no longer attached?

The LEDs on the MAX30101/MAX30102 can be used not only for Heart Rate and SpO2 measurements but also for proximity detection. This allows the LEDs to be inactive, saving power while not in use. When the user applies a finger or straps the device to the wrist, the SpO2 or HR function is initiated. This can also be used to detect the removal of the device. For the MAX30101 and MAX30102, the integrated proximity mode only works with the red LED (LED 1). When the SpO2 or HR function is initiated (by writing the MODE register), the RED LED is activated in proximity mode with a drive current set by the PILOT_PA register. When an object is detected by exceeding the RED ADC count threshold (set in the PROX_INT_THRESH register), the part transitions automatically to the normal SpO2/HR Mode. By reentering proximity mode periodically, the proximity detection can detect when the device is no longer connected to the used as the LEDs will be inactive. To reenter proximity mode, the MODE register must be rewritten (even if the value is the same). The proximity function can be disabled by resetting PROX_INT_EN to 0. In this case, the SpO2 or HR mode begins immediately. Alterntatively, this procedure can also be implemented through software for any of the LEDs available in the sensor. For an IR software proximity sensor use the below pseudo code: Initial Setting – SW proximity mode 0x0C 0x00 //RED LED: 0mA 0x0D 0x19 //IR LED: 5mA 0x0E 0x00 //GREEN LED: 0mA Only for MAX30101 0x0A 0x43 //SPO2 CONFIGURATION //SPO2_ADC_RGE : 8uA (this is a good starting point, try other settings in order to fine tune your design), //SPO2_SR : 50HZ, LED_PW : 400us 0x08 0x00 //FIFO CONFIG 0x11 0x12 //Multi-LED 1 0x12 0x00 //Multi-LED 2 0x04 0x00 //FIFO RESET 0x05 0x00 //FIFO RESET 0x06 0x00 //FIFO RESET 0x09 0x07 //Mode Configuration : Multi-LED Mode 0x02 0x40 //PPG RDY Interrupt Enable current mode = proximity IRQ Handler Read 6 bytes from FIFO(first 3bytes : IR, next 3bytes : RED) If ( IR Count > 2000 and current mode == proximity ) { 0x0C 0x? //RED LED: desired LED current for RED 0x0D 0x? //IR LED: desired LED current for IR 0x0E 0x? //GREEN LED: desired LED current for GREEN Only for MAX30101 0x0A 0x4E //SPO2 CONFIGURATION SPO2_ADC_RGE : 8uA, SPO2_SR : 400HZ, LED_PW : 400us 0x08 0x40 //FIFO CONFIG : SMP_AVG : 4 Samples : 100 Hz ODR current mode = HRM_SPO2 } else if ( IR Count < 5000 and current mode == HRM_SPO2 ) { 0x0C 0x00 //RED LED: 0mA 0x0D 0x19 //IR LED: 5mA 0x0E 0x00 //GREEN LED: 0mA Only for MAX30101 0x0A 0x43 //SPO2 CONFIGURATION SPO2_ADC_RGE : 8uA, SPO2_SR : 50HZ, LED_PW : 400us 0x08 0x00 //FIFO CONFIG current mode = proximity }

How to avoid water condensation inside the MAX30101/5?

Unfortunately the 14 pin OLGA package has a vent hole at the bottom and this cannot be avoided, you need to use the device in a noncondensing environment. This is the risk of open packages. If you seal it, a strong pressure differential might cause lid to break/pop off.

In Multi-LED mode, if SLOTx in the MAX30101 is disabled will I receive dummy bytes?

If a SLOTx is not active in Multi-LED mode then once the samples for the active slots have been taken, the FIFO will move on to the next sample. There are no dummy bytes generated. For example, with only RED and IR LEDs used. This means that both the RED and IR channels will each generate three bytes (2x3 bytes) in the order they are set in the SLOTx and then return to sample the first channel again.

Does Maxim offer Algorithm of SpO2 and HR Calculation in PPG solution?

Maxim Offers MAX32664GWEA+T for customer to acquire data from devices such as MAX30101, MAX30102 etc and calculate SpO2 and Heart rate. Customer only need to use his own MCU to communicate with MAX32664GWEA+T to control and transmit data. So that customer do not need time to work with ALGO and customer do not need additional flash and ram to store the tempo original data.

How to minimize error due to the self-heating effect of the LED’s in the MAX30101?

A large thermal mass should be provided on the PCB to sink heat out of the MAX30101 via pins 8-10. As this thermal pad can also conduct heat into the part, these pins should be oriented as far from any external heat source as possible. Ideally, the component should be oriented such that any heat from an external source is centered along its axis to minimize any thermal gradients across the pins/die.

Is the SLOTx[2:0] 000b value in the Multi-LED Mode Control Registers the same as 100b for the MAX30101/2?

Yes. Both values 000 and 100 will disable the slot of the relevant SLOTx[2:0] and the LED PULSE AMPLITUDE SETTING for that slot will be disabled. Note: The slots should be enabled in order. SLOT1 should not be disabled if SLOT2, SLOT3 or SLOT4 are enabled.

Is it recommended to use two green LEDs for heart rate measurement using the wrist?

Many HR wrist bands use 2-LEDs. However, they are typically matched, positioned symmetrically to the Photodiode centroid, have the same height, and implement optical walls to reduce cross coupling. One external LED can be used with MAX30101 to have two LED solution with one embedded and one external LED. However, matching is not viable as the external LED needs to be exactly matched with the embedded LED. In addition an optical barrier (i.e., light absorbing wall) is recommended between an external LED and the Photodiode.

Can the systolic blood pressure be obtained from the PPG and ECG signals?

While there is no direct way to obtain the exact value of blood pressure from PPG and ECG signals, mathematical models can be used to estimate the blood pressure information. A popular way of doing so is to use ECG-PPG heartbeat pairs to determine pulse transit time (PTT) measurement which is then used in a PTT&HR-SBP model for systolic blood pressure application. You may find the following links to be quite useful: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5294811/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4512231/

What are the optimal current values for the LEDs in the MAX30101 for wrist-based biosensor measurements?

You can use the following settings as a starting point for wrist-based measurement. The green LED generally needs much more current than the red and IR for good results. To evaluate the quality, you should place the module against your wrist and then plot each color vs time and look for distinctive peaks for each heart beat. If the plot shows a straight line, then the ADC is saturated and the LED current is too high. If you just see noise, try increasing LED current or adjusting the sensor on your wrist. Here are the recommended starting point settings: Pulse width: 411us ADC Full Scale: 8192nA Red: 10mA IR: 10mA Green: 50mA