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ADS8900BEVM-PDK: Hookup for software control debug/validation?

Dave Nadler
Intellectual 365 points
Part Number: ADS8900BEVM-PDK

I purchased the eval kit. It has lots of great stuff for looking at ADC fine resolution, however....
The analog qualification of the part is already done.

What I need to do now is hook the AD8902 to a micro-controller and validate software, proper control of the device, SPI timing, etc.
For this stage of development 4-bit resolution is enough! No fancy references or signal conditioning required!
I need a pot input, and external 5v (not 5.2v) supply, and hookups to conv/reset/SPI.

Sooo... How can I hook up the eval kit for the software debug/qualification task?
Or does someone know of a more suitable breakout board for this part?

Thanks!
Best Regards, Dave

  • 0
    TI__Mastermind 46360 points
    Hello Dave,

    The ADS8900BEVM is the only board TI has available for the device. You can wire your own MCU into this board for software testing. The EVM User's Guide has the schematics included.

    For power, provide 5.5V to the EVM_REG_5V5 net, and 3.3V to the EVM_DVDD net.

    To talk to the device, you can use as few as 4 lines, and each line is available on 0ohm jumpers on the board.

    Short /CS, CONVST together as a single /CS line. (R35)
    SCLK (R37)
    SDO-0 (R43)
    SDI (R47)

    Of course, all digital IO lines are available if you want to use the RESET, CONVST, RVS or multiple SDO lines.

    Regards,
    Keith N.
    Precision ADC Applications
  • 0 in reply to Keith Nicholas
    Intellectual 365 points
    Got it regarding the 0 resisters for the signal inputs, I'm looking at the schematic.
    I can source 3.3v from the MCU board OK. However...

    I have 5v available (from USB supply on MCU board), but not more than 5v.
    Do I have to remove the precision reference and supply the 5v2 net with 5v0 ?

    Also, how do I convert this to a single-sided (not differential) input, so I connect a test pot?

    Thanks!
  • 0 in reply to Dave Nadler
    TI__Mastermind 46360 points
    Hello Dave,

    If you just need basic functionality to test software, then you should be able to use a 5V supply for the 5.5V input. The 5.2V regulator and the reference will be in dropout (output will not be regulated), but the ADC should still have basic functionality. However, I have not had a chance to test this, so recommend finding a lab supply that can be set to 5.5V. (You need less than 100mA to power the board.)

    For the input, you can leave the negative input floating, and just adjust the positive input between 2.3 and 2.7.

    Regards,
    Keith
  • 0 in reply to Keith Nicholas
    Intellectual 365 points
    OK, I got this working with mods below.
    It would *REALLY* help customers like us if you could:
    - add vias without solder mask by each pin to allow us to easily solder patch wires
    - place a dumb pot on the board (with easy single-end configuration) for this kind of testing/integration work
    Thanks!
    Best Regards, Dave

    1. Remove R28 (disconnects on-board 5v reference, which requires the 5.2v we don’t have).
    2. Power: Connect gnd to MCU GND
    3. Power: Connect 5.2v net to MCU 5v supply (same as DAC board)
    4. Power: Connect EVMDVDD net to MCU 3.3v
    5. Connect reference input (at R28, U11 ADC pin 3) to 5.2v net
    6. Connections for digital control with long pins for scope:
    1. PA0 – R34 (conversion strobe input)
    2. PB14 – R35 (CS)
    3. PB0 – R37 (SCK)
    4. PA10 – R47 (MOSI)
    5. PA12 – R43 (MISO)
    6. PA3 – R32 (RST)
    7. jumper PA0 to PA2 (so MCU can simulate external conversion strobe using timer9 CH1)
    8. set up single-ended input:
    1. remove R48
    2. remove R50
    3. install 0 ohm at R18 (ties ADC -input to ground)
    9. Pot:
    1. pin 1: first end: ground
    2. pin 3: second end: 5v (5.2v net on board)
    3. pin 2: tap: U11 pin 9 (available at R48 pad)
  • 0 in reply to Dave Nadler
    TI__Mastermind 46360 points
    Hi Dave,

    I am glad to hear that you got this working! I appreciate your feedback on how we can make our EVM's easier to work with. I will definitely consider this on future EVM's.

    Regards,
    Keith