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Original question:

ADS1220: one question about the power down mode of ADS1220

ADS1220 POWER DOWN between conversations

Arthur Buchta
Prodigy 10 points
Other Parts Discussed in Thread: ADS1220

Hello,

Currently I’m reading the ADS1220 with ppi in single-shot mode with 600 Hz, which works fine.

With a tx-buffer I’m sending the Start/Sync, READ DATA command and reading the data (tx_buffer = [0x08, 0x10, 0xFF, 0xFF, 0xFF])

The Problem:

I connected the bridge GND to AIN03 and set the Low-side power switch to automatic, to reduce power consumption.

I expand my tx-buffer with the Power-Down command to open the Low-side power switch after conversation.

Now I’m getting corrupted data …

Is it possible to open the Low-side power switch between conversations?

 Greetings

Arthur

  • 0
    TI__Guru** 112965 points

    Hi Arthur,

    Welcome to the E2E forum!  I think your problem is mostly procedural.  You are sending the START/SYNC command immediately followed by the RDATA command.  The START/SYNC command starts a new conversion or restarts a conversion if one is already in progress.  The RDATA command reads the last completed conversion result.  So you are always reading the previous conversion result.  You should be sending the START/SYNC command and waiting for the conversion to complete (by monitoring DRDY) then read the conversion result.

    When you add the POWERDOWN command, the analog portion of the ADS1220 will power down and open the low-side switch.  When the next START/SYNC command is issued, the ADS1220 will wake up, but you are now reading the old (or last completed) conversion result.  Most likely there is some analog settling while the load cell is powering up and replenishing any capacitors in the measurement path.  This settling period is likely a part of the issue you are seeing.  

    Best regards,

    Bob B