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BQ25882: About built-in ADC accuracy

Tsukui Yusuke
Guru 21930 points
Part Number: BQ25882
Other Parts Discussed in Thread: BQSTUDIO

Hi,

Customers plan to use the built-in ADC to monitor charging current and voltage.
However, there is a discrepancy between the measured data and the ADC sense result.
Could you tell me the ADC sense data accuracy information to confirm the practicality of the built-in ADC?



Best regards,
Yusuke

  • 0
    TI__Genius 10385 points

    Tsukui-san,

    Could you elaborate further on the customer's measurement setup and what their results were?

    How significant was the delta between the measured, expected, and ADC reported result?

    Thanks,

    Ricardo

  • 0 in reply to Ricardo
    Guru 21930 points

    Hi Ricardo,

    Thank you for your reply.

    We measured it using EVM and bqstudio.
    To get an overview of ADC accuracy with EVM,
    we tested it with a charging voltage of 8.4V and a charging current of 100mA.

    ・Multimeter result is 99mA
    ・ADC sensing result is 75mA (bqstudio)

    From the above results, it was found that ADC sensing has rough accuracy.
    Customers want ADC sensing accuracy information when the ICHG is:

    ・50mA
    ・20mA
    ・2mA

    Could you tell me ADC sensing accuracy information for the above charging current conditions to decide whether to use the ADC?

    Best regards,
    Yusuke

  • 0 in reply to Tsukui Yusuke
    TI__Genius 10385 points

    Yusuke-san,

    I will follow up with you on Wednesday (Dallas time) with information regarding the ADC accuracy.

    Thanks,

    Ricardo

  • 0 in reply to Ricardo
    Guru 21930 points

    Hi Ricardo-san,

    Thank you for your kind support.
    I understand the situation.
    We look forward to hearing from you.

    Thanks,
    Yusuke






  • 0 in reply to Tsukui Yusuke
    TI__Genius 10385 points

    Yusuke-san,

    I am observing similar behavior on my side as well. Unfortunately we do not offer any performance warranty on the ADC accuracy. Additionally at such low currents the signal going into the current sense amplifier is pretty small. This makes the resulting ADC read out subject to inaccuracy. 

    If sensing currents this small is a customer requirement, then an external current sensing solution should be applied.

    Thanks,

    Ricardo