ADS4129EVM: D0/D1 Data Output Lines Not Showing Desired Signal

Will Harrison

Part Number: ADS4129EVM
Other Parts Discussed in Thread: ADS4129

Tool/software:

Hi All,

I am working with the ADS4129 ADC and experiencing an issue where the two least significant data output lines (D0/D1) are always stuck at fixed values (0.8 V and 1.25 V) and show no toggling or valid signals. I am using the test pattern and controlling the ADC via SPI. All other data lines output signals as expected. I have probed the pins of the ADC itself and all other data lines (D2-D11) are showing the correct output, but D0/D1 doesn't change. I have tried two separate EVM boards, both resulting in the same issue.

0x00 - 0x02 (initial reset)

0x42 - 0x08 (disable low latency mode to activate digital functions)

0x25 - 0x04 (ramp test pattern)

Any help would be greatly appreciated.

Thanks,

Will

28 days ago

0 Rob Reeder 28 days ago

TI__Mastermind 37660 points

Hi Will,

When you configure the ADC in bypass mode and sample a signal do those bits, D0/D1, toggle then?

Regards,

Rob

0 Will Harrison 28 days ago in reply to Rob Reeder

Prodigy 10 points

Hi Rob,

Thank you for the very prompt response.

I just tried switching to this and it has the same result, all other pins are showing a signal but still no change on D0/D1.

Thanks again,

Will

0 Rob Reeder 28 days ago in reply to Will Harrison

TI__Mastermind 37660 points

Thanks Will,

I assume you restarted the device/powered down and tried this?

Any other register writes that were applied?

Regards,

Rob

0 Will Harrison 28 days ago in reply to Rob Reeder

Prodigy 10 points

Yes, I restarted the device before retrying. For the bypass test I only wrote to register 0x00 with value 0x02 to reset it

0 Rob Reeder 28 days ago in reply to Will Harrison

TI__Mastermind 37660 points

Hi Will,

Just to confirm, you are checking this on a TI EVM?

If so, what data capture board are you using for this setup?

Thx,

Rob

0 Will Harrison 28 days ago in reply to Rob Reeder

Prodigy 10 points

Yes, I am using the TI ADS4129 EVM board (ADS41XX/58B18 Evaluation Module).

I am using a Zynq Ultrascale+ FPGA with a custom interposer board.

I have disconnected the EVM board from the rest of the setup so it is only powered and I have configured it using the USB interface via the TI GUI.

However, even with this isolated setup, I still have the same result when probing the pins of the ADC chip (all showing expected signals except for D0/D1)

0 Rob Reeder 28 days ago in reply to Will Harrison

TI__Mastermind 37660 points

Ok, thank you for the details Will. This helps.

I have an EVM and will try this in the lab today, I will update you by the end of today.

Thanks,

Rob

0 Rob Reeder 28 days ago in reply to Rob Reeder

TI__Mastermind 37660 points

Hi Will,

I checked out an EVM in the lab and D0/D1 are switching just fine, like the other bits.

I checked a few times in different scenarios.

Anyway, can you please check and see if there are any shorts on the RN resistor networks? RN1-6?

Regards,

Rob

0 Will Harrison 27 days ago in reply to Rob Reeder

Prodigy 10 points

Hi Rob,

Thanks for checking this and for your help.

There doesn't seem to be any shorts, I have checked the resistance from each adc pin to ground and power supply, both showing resistances in the 100,000s. I also checked between the connector pads and the adc pins as well as across the corresponding resistor network pins and there was a resistance of ~0.5 Ohms for all of them.

I also checked for continuity between the power supply pins on the adc chip and all seemed to be working fine.

Thanks again,

Will

+1 Rob Reeder 27 days ago in reply to Will Harrison

TI__Mastermind 37660 points

Hi Will,

I am closing this post and will email you offline to figure out that is going on.

Please be on the lookout for my email.

Regards,

Rob

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ADS4129EVM: D0/D1 Data Output Lines Not Showing Desired Signal