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ADS1281EVM-PDK: ADS1281EVM

KIYOSHI ARAI
Prodigy 40 points

Part Number: ADS1281EVM-PDK

I use ADS1281EVM with single power.

So -5V is not supplied.

Jumper J7-4 AVSS is open because it will be connected to the -2.5V U13 output.

AVSS in the on-board circuitry does not appear to be connected to GND.

What are the conditions for using this board with bipolar power?

Where should AVSS be connected for single power?

Please give me instructions on how to connect J7-4 when using single power.

  • 0
    TI__Mastermind 18900 points

    Hello Kiyoshi-san,

    For the shortest answer to most of the questions is follow the procedure in the user guide to supply the correct voltage rails to the MMB0 board and then open up the GUI and change the appropriate settings. The EVM has the hardware to swap between bipolar and single supply voltage automatically.

    Detailed answer:

    But in general, the GUI is supposed to start up and GPIO3's state determines the bipolar or uniploar supplies are used. If GPIO3 is low, then AVSS is connected to GND (Q3 and Q2) and AVDD is supplied to 5V (Q1). If GPIO3 is high, bipolar supplies for the ADS1281 need to have AVSS = -2.5V (U13) and AVDD = 2.5V (U10). Note, that the 5V, 10V, -10V, -5V, and 3.3V all come from the MMB0 board (J8). 

    As described in user guide, a lot of the voltage are derived from the voltages on the MMB0 board, the schematic for it can be found here: https://e2e.ti.com/support/data-converters-group/data-converters/f/data-converters-forum/775258/faq-what-documentation-is-available-for-the-mmb0

    All of these statements operate under assumption that J7 shunts are covered at all times. If they are disconnected, the user is expected to supply those voltage directly at J7 as there is no direct connection from the voltage supplies to the pins.

    That being said, the linked post shows a user who's 5V input on the MMB0 board was damages as a result of starting up in unipolar so they removed the inverter on GPIO3 (U8) and permanently tied it to the 5V input. This post should has more detail if you want to start up the EVM in bipolar supply mode every time to avoid potential damage: https://e2e.ti.com/support/data-converters-group/data-converters/f/data-converters-forum/1124398/ads1281evm-pdk-why-is-gpio3-high---i-want-bipolar-mode 

    Hope this helps.

    Best,

    -Cole