Does ADPD103 parameters is very critical for noise?


i am using ADPD103 in our PCB(not adi evm), now we use default parameters and run at normal mode, but very noisy, is that any suggestion?

  • 0
    •  Analog Employees 
    on Jul 28, 2016 7:39 PM

    Hi leelose,

    Have you tried to do an AFE timing sweep as explained in the datasheet in the "Sweeping the AFE Position" section to determine that you have optimised timing? Can you tell me more about your circuit and configuration? It will be also important that you have a quiet power supply with 0.1uF decoupling capacitors very close to each of the supply pins and a 1uF capacitor on the VREF pin. Does your PCB use a ground plane with low inductance connections to the GND pins of the device?

    Regards.

  • Hi Buckley,

    thank you for your response, i already tried AFE timing sweep by using register 0x39,0x3B and optimize led timing(0x30,0x35,0x31,0x36) as considerate SNR, our PCB supply led voltage is 5V(Infrared is most lower VF ~1.15V) is that any suggestion about VLED? In our circuit, we use decoupling capacitors in all supply pin and already very close, and 1uF at VREF pin, and a 4.7uF at VCC_LED but close at LDO not the led anode, and the PCB GND plane is big. Do you have any optimize parameters in adpd103? and any sample code to reference?

    Best Regards,

    leelose

  • 0
    •  Analog Employees 
    on Aug 1, 2016 5:25 PM

    Hi leelose,

    There is 3.6V maximum voltage allowed on the LED driver pins, so you need to make sure that you use an LED supply voltage that ensures that the cathode of the LED does not exceed 3.6V. For example, with a 5V LED supply and IR LED Vf of ~1.15V, the driver pin of the ADPD103 would be at ~3.9V which is outside of the maximum specified voltage of 3.6V, so you need to use a smaller LED supply voltage for the IR LED.

    Regarding the noise issue you're having. Could you please tell me what you're seeing for noise that you believe is outside of the specs of the device?

    Regards.

  • hi Buckley,

    thanks for your notice, i change my voltage and follow the spec. noisy is reduce some, and i adjust the the LED timing and AFE timing also reduce some noise, but once i tune a optimize parameters, then another day i use these optimize parameters won't get same SNR, it mean that i want to tune the parameter every time? and the internal clock always must calibration when first time power startup?

    all the condition are follow the spec definition, i think the most problem is my parameters?

    Best Regards,

    leelose

  • 0
    •  Analog Employees 
    on Aug 3, 2016 5:30 PM

    Hi leelose,

    Optimized timing parameters would not need to be changed every time assuming that the sensor you have connected to the ADPD103 is not changing its characteristics over time. If the sensor is changing, then you may need to do periodic optimizations and calibrations. The internal clock can drift with temperature and over time so it is a good idea to do a clock calibration at power up.

    Regards,

    Kevin