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ADAU1451WBCPZ-RL - Recommendation details (Pull up / Pull down / Floating) for ADC pin not used

Hi,
Could you please share the Recommendation details (Pull up / Pull down / Floating) for ADC pin when it is not used in the ADAU1451WBCPZ-RL DSP
Please provide the information as soon as possible.

Thanks in advance

Thanks & Regards,

Thangaprabu S

  • Hello Thangaprabu,

    These are AUX ADCs which are SAC type of converters. So the pin is not up on a common mode voltage so you can ground these pins if not used. 

    They can be left floating however, for applications where the device might be in a high RF or EMI field, where pins cannot be left floating then you can ground the pins. 

    Thanks,

    Dave T

  • Hi Dave,

    Thanks for the information. Could you clarify the below point

    1) Whether single pull down resistor 10K ohm is sufficient to connect all the  AUXADC0 to 6.(i.e. All ADC pin is tied together & connected to the 10K ohm pull down resistor) 

    2) Could you please share the Recommendation details (Pull up / Pull down / Floating) for other pin (GPIO/I2S/I2C/SPI/SPDIF/THD) pin also when it is not used.

    Thanks & Regards,

    Thangaprabu S

  • Hi Dave,

    Please update the above request.

    Thanks & Regards,

    Thangaprabu S

  • Hello Thangaprabu,

    1) Whether single pull down resistor 10K ohm is sufficient to connect all the  AUXADC0 to 6.(i.e. All ADC pin is tied together & connected to the 10K ohm pull down resistor) 

    These pins can be grounded. You certainly could put a resistor to ground but no need for it. 

    2) Could you please share the Recommendation details (Pull up / Pull down / Floating) for other pin (GPIO/I2S/I2C/SPI/SPDIF/THD) pin also when it is not used.

    Set the GPIO pins to be an input ( that should be the default setting), then ground the pin.

    I2S:

    Clock pins: If the serial port is not being used then set the pins to be an input and ground the pins. If you have to set the clocks to master and not use the pins. Which is sometimes the case, then use a 10K to ground. 

    SDATA Pins, for the SDATA input pins, ground them. For the SDATA output pins, use a 10K to ground. 

    THD pins. You can ground these. 

    SPDIF, leave floating, they are internally terminated but you can use a 10K to ground for the output. For the input, put a cap to ground. A small cap is good enough, 0.1uf is fine. The value is not very critical.

    By the Way, this is listed in the datasheet in the pin descriptions:

    " If terminations on all pins is required, this pin can be terminated with a 100 nF capacitor to ground. If a lower cost method is desired, this pin can be grounded to DGND. This pin draws approximately 0.1 mA when grounded."

    I2C or SPI.

    Are you talking about the master comms port? If the pin is unused then pull up the SS pin to IOVDD. 

    For the MOSI_M and SCLK_M pins tie 10K to ground.

    For the MISO_M a 10K to ground. 

    For the slave comms port I would be surprised if these are not being used. 

    Dave T

  • Hi Dave.

    Thanks for the detailed explanation.

    Thanks & Regards,

    Thangaprabu S