How to drive an OLED for PPG in ADPD4001?

Hello everyone!

I am using the ADPD4001 for ECG and PPG measurement, however, for a low-power device, I am using an OLED light source. My OLED works at 100uA maximum. However, the driving current sunk on the ADPD4001 is a minimum of 2mA. Can you advise me on how to lower the current pulled? Would a resistor in series with the OLED work?

I think of a current divider with 2 resistors, but I'm not so sure it would work, and I don't want to burn my OLED on every try.

Parents
  • 0
    •  Analog Employees 
    on Jul 15, 2021 7:20 PM

    Hi there,

    Thanks for reaching out!

    The ADPD4001 LED drivers, which are current sink, have minimal current of 2mA. These are  2-3 µpulses though. The average current is much smaller.

    Is there any specific reason for choosing the OLED as your light source for your PPG measurement? What is luminous flux power of your OLED? In PPG measurement, the luminous flux power is an important factor that determines the SNR of the photocurrent.

    Regarding power, ADPD4001 uses 2-3 µs pulses for PPG measurement, which gives ADPD4001 tremendous advantage in low-power design.   

    By the way, you may consider ADPD4101 for your design as ADPD4101 has better power and SNR performance than ADPD4001. 

    Regards,

    Glen B.

  • Hello Glen!

    Thank you for your answer. I am not at liberty of sharing my OLED characteristics, but I am curious about how to drive the OLED at a lower current on the ADPD IC.

    I think the ADPD should still sink ~200mA, but putting the OLED with a resistor in parallel on a current divider so the current through it is ~100uA might work. I am not sure though.

    Additionally, I checked the ADPD4101 datasheet, and it works in the same way as the 4001, but with better performance. Do you think I can just swap the ICs? (and keep my controller and power source)

    Thanks again!

  • 0
    •  Analog Employees 
    on Jul 16, 2021 6:06 PM in reply to mvalbanp

    Hi there,

    The shunt resistor as a current divider may work. You may want to check the voltage drop across the OLED at your targeted current and then select a shunt resistor accordingly.

    The ADPD4001 and ADPD4101 are pin-to-pin compatible while ADPD4101 has much better SNR and power performance. There is no need for hardware change although there are a few register changes.

    Regards,

    Glen B.

Reply
  • 0
    •  Analog Employees 
    on Jul 16, 2021 6:06 PM in reply to mvalbanp

    Hi there,

    The shunt resistor as a current divider may work. You may want to check the voltage drop across the OLED at your targeted current and then select a shunt resistor accordingly.

    The ADPD4001 and ADPD4101 are pin-to-pin compatible while ADPD4101 has much better SNR and power performance. There is no need for hardware change although there are a few register changes.

    Regards,

    Glen B.

Children
No Data