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TPS65987DDJ: ADCIN2 connection to get I2C_ADDR_DECODE 011b

Antony Lin
Genius 13480 points
Part Number: TPS65987DDJ

Hi,

In the EVM, to get I2C_ADDR_DECODE @ 011b we see ADCIn2 is connected to a resitive divider of 10Kohm vs 100Kohm.  Meanwhile, in the datasheet there's a description as below which shows it's workable to connect ADCIN2 to LDO_3V3 directly.  But, with ADCIn2 conencted to LDO_3V3, we sometimes see a yellow mark in Windows Device manager for TPS65987DDJ (with i2C connected to PCH).  But, the same issue is not seen if we connect 10kohm vs 100kohm.  Can you confirm if it's ok to connect ADCIN2 to LDO_3V3 directly? 

Thanks!

Antony

  • 0
    TI__Mastermind 36756 points

    Hi Antony,

    It is recommended to have a resistor divider present on the ADCIN pins. This will ensure that the ADC is correctly sampling the voltage on the ADCIN pin and not reading a false value. When directly tying the ADCIN pin to LDO_3V3, it is possible for the ADC to read an incorrect value on bootup and set the wrong I2C address. When connecting ADCIN pins through a resistor divider, this error cannot happen.

    Thank you,
    Eric

  • 0 in reply to Eric Beljaars
    TI__Genius 13480 points

    HI Eric,

    Thanks for your comments.  Considering customer already tied ADCIN2 to LDO_3V3 and encounter such unstable issue for the moment, is there any way we can force the I2C address to be 0x23 as desired by any FW setting in config tool?

    THanks!

    Antony

  • 0 in reply to Antony Lin
    TI__Mastermind 36756 points

    Hi Antony,

    Unfortunately, the I2C1 address is not configurable through the Host Interface. It is strongly recommended to use a resistor divider on the ADCIN pins to avoid these ADC read errors. 

    Thank you,
    Eric