ADS131 wrong ref voltage

Eyal Lasko

Other Parts Discussed in Thread: ADS131E08

HI,

We are using ADS131E08 in our design. It is configured to use internal Vref = 2.4V

When powered on (CONFIG3 = 0xCC) I measure ~1.2V on VCAP1 pin (as expected) BUT on Vrefp it measures only ~1.7V instead of 2.4V

What can be the reason ?

Thanks

over 8 years ago

0 Brian Pisani over 8 years ago

TI__Mastermind 38745 points

Hello E L55,

With respect to what voltage are you measuring VREFP? Is it VREFN which is tied to AVSS? If this is the case and the voltage still measures incorrectly, please post a copy of your schematic for me to review.

Regards,
Brian Pisani

0 Eyal Lasko over 8 years ago in reply to Brian Pisani

Expert 2300 points

Hi Brian ,

Thanks for your prompt reply.

I'm measuring VREFP-AVSS (AGND).

Attached is a screen cap of the implementation.

Note that there are some manual modifications to the schematic:

- C100 on AVSS replaced with jumper (top side)

- START was wired to the MCU

- DAISY_IN tied to DGND (resisotr removed)

0 Brian Pisani over 8 years ago in reply to Eyal Lasko

TI__Mastermind 38745 points

Hey E L55,

When you say you replaced C100 with a jumper, you shorted it to ground, correct? If this is the case, I don't see an issue with the schematic. How many boards have you assembled. Is it possible that there is a cold solder joint somewhere?

Regards,
Brian Pisani

0 Eyal Lasko over 8 years ago in reply to Brian Pisani

Expert 2300 points

Thanks.

Yes, C100 was replaced with 0 ohm resistor.

I'll cross check with other boards and respond here later.

0 Greg Hupp over 8 years ago in reply to Eyal Lasko

TI__Mastermind 23235 points

Hello E L55 -
Have you enabled the reference buffer? This is done by writing a 1 to the PBD_REFBUF bit in CONFIG3.

0 Eyal Lasko over 8 years ago in reply to Greg Hupp

Expert 2300 points

Hi Greg,

I did . And that was the problem.... :)

There was a contention between internal and external reference sources....

Data converters

Data converters forum

ADS131 wrong ref voltage