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FDC1004: Question regarding initialization time and peak current

Johannes Omberg
Prodigy 30 points
Part Number: FDC1004

Hi

We are using the FDC1004 in a small size portable device with a very small battery. To save energy we switch the sensor on and off by toggling the power supply to the FDC. At first the FDC wouldn't communicate on the I2C line but when we added a 5ms delay it worked. We also tried 2ms but it didn't work.

So questions:
1) How long time does the FDC1004 need to start up and begin measuring (disregarding any capacitance on the VDD)? I'm not sure if the issue is in the MCU or in the FDC.
2) When we start-up the FDC1004 we can see a peak current of 3.9mA. Is that normal? We expected 750uA at most.

Our design is copy pasted from the evaluation board except for different MCU and sensing part.

Best regards

Johannes

  • 0
    TI__Expert 3435 points

    Hi,

    We have received your question. I will get back to you in a day or two. 


    Regards

    Sharath.

  • 0 in reply to Sharath Vallamkonda
    TI__Expert 3435 points

    Hi,

    Thank you for providing detailed information regarding the issue you have. 

    1. I couldn't find startup time for FDC1004 devices. I cant provide a definitive answer as we are not testing this parameter on ATE. This could vary with temperature and voltage ranges. Is it possible for micro to try at 4ms and try again after 1ms until it starts communicating?

    2. How is this current measured? 750ua current consumption is during the normal operation mode, startup peak current could be little higher. Could it be the current consumed by the capacitor or other circuitry on your board?


    Regards

    Sharath.