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ADS1278: S2 DIP Switch Pin4 (F2) - Pulled High

joti1
Prodigy 70 points

Part Number: ADS1278
Other Parts Discussed in Thread: ADCPRO

I am using PCB Rev F of the ADS1278 EVM board and I am trying to configure the board to operate in SPI TDM Dynamic mode (F2=0,F1=0,F0=0)

However, it looks like F2 is always pulled high on S2 pin4 - regardless of the DIP switch setting.

I notice there is an errata document for this board that refers to an issue with the CLKDIV pin (pin 3 of S2) - however this pin seems operate as expected on my board and can be controlled by the DIP switch

Are there any known issues regarding S2-Pin4 (or could this be somehow related to the existing errata for this DIP switch)? 

thanks,

  • 0
    TI__Guru 51470 points

    Hi Joe,

    Do you have the ADS1278EVM plugged into the MMB0 board?

    The Format Pins on the ADS1278 are all inputs.  However, If using the MMB0 board to power the ADS1278EVM daughter board, it will pull the different IO lines high or low, and requires all switch positions to be open (down position).  The MMB0 and ADCPRO software defaults to the Frame-Sync-TDM-Fixed mode, which forces the F2 line high.

    You can operate the ADS1278EVM standalone with your own host controller, in which case, the dip switches are useful to configure the desired format, but the board should not be plugged into the MMB0 board in this case.

    Please note that SPI mode limits your SCLK to a maximum of 27MHz, which limits the maximum output data rate to 105ksps.  Also, CLKDIV must always be set high when using high-speed and high-resolution modes, per table 8 in the datasheet.

    Regards,
    Keith Nicholas
    Precision ADC Applications

  • 0 in reply to Keith Nicholas
    Prodigy 70 points

    Hi Keith,

    If I operate the ADS1278EVM in standalone mode what voltages will I need to provide from the host controller side?

    Do I need to provide 5.0v, 3.3v and 1.8v onto the J5 connector?

    Thanks

  • 0 in reply to joti1
    TI__Guru 51470 points

    Hi Joe,

    Yes, you need these three supply voltages.  Please note that these supplies on J5 connect directly to the power supply pins of the ADS1278.  If these voltages exceed the ABS Max specs, the part may be damaged.

    Per the ADS1278 Datasheet:

    Also, the user's guide has the DVDD/IOVDD labeled backwards.  It should state:

    The ADS1278 digital supplies are connected as follows:

    • IOVDD supply is connected to the +3.3VD pin of the J3 header.

    • DVDD supply is connected to the +1.8VD pin of the J3 header.

    The ADS1278 analog supply, AVDD, is connected to the +5VA pin of the J5 header.

    Regards,
    Keith