problems with ADS1158

Hi Francesco,

Can you possibly post your 2 sets of Gerber files here for us to review/compare?  I've got no 'good' explanation for your issues with the ADS1158, other than something may have been wired incorrectly.  If you don't want to post your files publicly, we can try to reach you directly through e-mail.

Hi Tom,

thank you for your reply.

I'll try to extract the ADS1158 wiring part from my gerber and send it to you. Could you provide a email address?

In any case I checked the new gerber against the old version with the guy who made the master and we didn't find any relevant difference. The schematic (and the netlist) of the part has remained the same. He chaged the layout a little, but I expect a bad working, not the coplete stop of the component.

Francesco

Hi Francesco,

As I understand it, you cannot read back the ID bits but when you use the pulse convert command, you have no problems reading back conversion results? This is not something that we have seen in the past. Have you tried to read back from other registers internal to the device to see if you have problems? Could you take a picture of your SPI transfer word for when you try and read back the ID bits so I can make sure there are no problems there. Let me think about this a little more and I will post if I think of something else to try.

Regards,

Tony Calabria

Hi Tony,

I apologise but I think I didn't explain correctly my problem.

1. I have designed a board using ADS1158
2. in the first release the converter was working correctly both in SPI mode (using the pulse convert command) and HW mode (using the start pin)
3. in the last release of the board I didn't change the part of the circuit because it was working properly
4. the only modification consist in a minor rearrangement of the layout (eg.: a capacitor was moved from top to bottom,...)
5. in the last release the ADS1158 doesn't work at all
6. there are a lot of components attached to the SPI bus and they all work properly
7. I have checked all power supply and Vref and they are ok

via SPI

1. I have tried to read the converter ID but unsuccessfully
2. I have tried to start conversion (using the pulse convert command) but unsuccessfully
3. I have compared the SPI signals with the old version of the board and they are the same

Therefore I have checked the gerber files looking for a mistake but unsuccessfully.

After this I thought there might have been a problem of noise on the SPI. If it is so the ADS1158 could not understand the request, but if it is not broken it should respond to teh Start pin change.

I have arranged a 100uS pulse on the start pin looking for a /DRDY change but unsuccessfully.

I think at this point that the component is broken.

My question now is how can the ADS1158 have been broken? What kind of situation could damage the component this way?

Thanks

Francesco

Hi Francesco,

I have reviewed your Gerber data as well and see no major change from revision one to two.  You should not have any issues with the DVdd supply being at 5V, the digital side of the chip can range from 2.7 to 5.5V.  Have you been able to verify that your crystal oscillator is starting up?  You might want to verify as well that there is no large voltage differential between DGND and AGND (the AVSS pin) - I don't see in your Gerber files how you reference them together. 

Great news!  Thanks for letting us know.