ADPD188gg Heart rate in wrist mounted wearable

Hi,

I'm evaluating using the ADPD188GG for a wrist mounted wearable.

In my application I would only need to calculate an average BPM in different activity during a normal day (standing still, walking, small sprints).

I already have a design and algorithm for the activity recognition based on an M4 ble chipset (nrf52) and a low power accelerometer and would like to know if someone has successfully implement an algorithm for wrist mounted Heart rate using the ADPD188GG, I'm especially interested in the motion compensation.

Does Analog supply an algorithm? 

Thanks

  • +1
    •  Analog Employees 
    on Sep 11, 2020 3:20 PM 2 months ago

    Hi,

    We're supporting heart rate through field sales based on the size of the opportunity.

    Could you please fill out this:

    https://form.analog.com/form_pages/support/integrated/techsupport.aspx

    We cannot do anything here on EZ. 

    Thanks,

    Yigit

  • Thanks for the reply. I'm talking with the sales team. 

    I have a small technical doubt, at page 38 of the data sheet in the chapter "float mode for synchronous LED measurements", the float mode is proposed as a way to lower the current of the LEDs and the voltage drop so a boost converter can be omitted (very interesting). Is this applicable also to the internal LEDs? Because at page 4 the VLED1 has a minimum of 4V and I can't find anywhere a VF/I of the internal green LEDs.

    Thanks for the support

  • 0
    •  Analog Employees 
    on Sep 24, 2020 9:45 PM 1 month ago in reply to Zucky

    That statement is true for the ADPD1080, which is the AFE inside ADPD188GG module. Float mode allows you to operate under low CTR (current transfer ratio) conditions. It is a different type of measurement compared to the normal operating mode, it allows you to accumulate charge on photodiode for a period of (float) time that you set and that's why under low PD current/low light conditions, it allows you to use the chip efficiently. Keep in mind that float mode is typically recommended under low PD current/low light conditions and not under normal conditions, because it is typically very prone to ambient light. If there is ambient light, it will cause TIA and/or ADC saturation, or at the very least, a noisy measurement because ambient light rejection is inferior compared to the normal operating mode. You will see the ambient light effect much more with float mode, so please be cautious to it. But if there is no ambient light, it is certainly super helpful in some cases. 

    That being said, that statement is a bit tricky when it comes to the internal green LEDs. You can use ADPD188GG with any type of LED, that's why it's a correct statement for ADPD188GG if the external LED you choose allow you to do it, also taking the compliance voltage of the ADPD1080/ADPD188GG LED driver into account. Basically it all depends on the LED forward voltage requirements.

    We don't officially recommend you to use lower than 4 V for the internal green LED supplies though, because 4 V is already close to the low end of the supply voltage requirement for a reasonable LED current. Therefore, you will need to make sure you characterize your system properly. If you supply too low voltage, you may not get the luminous flux that you would want, so that could cause an issue in your system even if you use float mode with a long float time to accumulate charge.

    Just as a side note, typically green/blue/UV LEDs require a higher supply voltage. You could still find some that require a lower supply voltage for a certain current, but they are typically more expensive. 

  • 0
    •  Analog Employees 
    on Sep 24, 2020 9:52 PM 1 month ago in reply to Yigit Yoleri

    As a clarification, you could theoretically use lower than 4 V to a low extent of LED current, but we do NOT recommend it officially because it may cause you to get lower performance than you would want.

  • Thanks for the fast reply. We are going to use the boost then for the LED supply. Better to be safe.