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ADS1120EVM: Gerber request for board.

Tor Hansen
Prodigy 120 points
Part Number: ADS1120EVM
Other Parts Discussed in Thread: ADS1120, ADS1147

Hi,

I would like to get the Gerber for the ADS1x20EVM?

The analog GND and digital GND are constantly connected on the board.

This means it is not possible for me to test a +-2.5 V supply on the analog supply. AVDD can be switched in/out by jumpers.

But, AVSS is always connected to DGND on the ADC, I suggest you add a jumpr to enable this option on future boards.

I hope, i via the gerbers can disconect the AVSS for the DGND on the ADC.

best regards

Tor

  • 0
    TI__Guru** 112725 points

    Hi Tor,

    Thanks for your comments.  When the EVM was developed, there was a good deal of discussion as to what features were to be added which included a bipolar supply option.  Due to limited board space available and the primary customer target for the ADS1120 was for those primarily requiring the ability to use a unipolar supply only, the bipolar supply option was left out.  In addition, adding a jumper would add inductance to the AVSS which could effect performance for single ended measurements via the mux.  We also felt that it would be too easy for a customer to exceed the absolute maximum supply input voltage specifications by accidently leaving AVDD connected to +5V while connecting AVSS to -2.5V.  So in the end the bipolar connection was made deliberately hard.

    The easiest way to connect a -2.5 V supply is to unsolder pin 5 from the PCB and carefully lift the pin and solder a wire for an external supply connection to the pin.

    A more complicated approach is to remove the ADS1120 and cut the traces to ground at the points indicated in the picture below under the device and also along C1 (board top layer).  You can scrape back the solder mask and attach (solder) a wire for an external connection.

    7840.6544486_ADS1x20_Gerbers.zip

    To increase our understanding, is there a particular sensor or special need to use a bipolar supply?  Is the increased impedance using the PGA enabled required for your measurement?  What type of performance are you hoping to achieve?

    You could also consider the ADS1147EVM which has a built in capability for +/-2.5V.  The ADS1147 is very similar in capability except for the low-side switch and the PGA disable contained in the ADS1120. 

    Best regards,

    Bob B