Doubts regarding a CS5530 ADC circuit

[floxia]

Hi there,

I have been working on this for a few days now and am kind of stuck, so I have decided to reach out to the community to see if anyone can shed some light on my doubts regarding the following circuit.

The circuit I have drawn is based on the reference design for the CS5530 provided by Cirrus Logic.


I aim to design a loadcell (Wheatstone bridge) weigh indicator capable of reading 40000 intervals, where the transducer allows it).
Although it will not be used to read 40000 intervals, I would like to set that as the target for the project.

I will list all my doubts, even though I do not expect all of them to be answered, to avoid creating multiple repetitive posts.

My doubts are as follows:

1. How can I supply VD+ and VA+? Can they be the same 3V3 or 5V rail coming from an LDO?
2. From the schematic, it is possible to see that Vref from the LT1019 is 2.5V; would it not be better to use the 5V version of the LT1019 to create a 5V excitation for the bridge?
3. Can VD- and VA- be tied to the same ground plane?

So far, this is what I have been able to draw:





In the first schematic, I have kept the digital voltage separate from the analog voltage as per the Cirrus schematic, while in the second schematic, all the grounds are tied to the same ground plane, or at least that is what I was trying to achieve.

I am new to this, so I apologise if something is missing or unclear; any help will be greatly appreciated!

Edit:

I am not able to attach the images inline; I hope it will still be clear.

[dietert1]

Didn't use the Cirrus CS5530A before, but the TI ADS1256 and ADS1263 that are similar. Recommended reference voltage for all of them is 2.5 V. Ready-made ADS1256 boards are available at ebay and amazon. They include a 3.3 V voltage regulator for the digital circuitry in the chip and an ADR03 reference with a low pass filter.
Easy to find more comments in this forum.

Regards, Dieter

[floxia]

Didn't use the Cirrus CS5530A before, but the TI ADS1256 and ADS1263 that are similar. Recommended reference voltage for all of them is 2.5 V. Ready-made ADS1256 boards are available at ebay and amazon. They include a 3.3 V voltage regulator for the digital circuitry in the chip and an ADR03 reference with a low pass filter.
Easy to find more comments in this forum.

Regards, Dieter

Thanks dietert1, for the input; the reason for me to use the CS5530 is that I have a commercial scale indicator to compare, and since I was happy with its accuracy and speed, I wanted to use that as a guide. Furthermore, the price of the CS5530 compared to the ADS1256 is far smaller, considering that I will never use the 4/8 inputs of the ADS1256.

Although before moving to the CS5530, I had indeed bought an ADS1256 board with an integrated STM32 (I have attached a picture of it), I was never able to get the SPI communication to work. Therefore I have abandoned the project as I am not sure if the board is faulty or if I am faulty!

Perhaps I should post a question in the microcontroller section on the forum to see if someone will know how to get that going.

[dietert1]

Did you try one of these?
https://github.com/yasir-shahzad/CS5530
https://github.com/majialou/STM32F1-ADS1256-Data-Collect
https://curiousscientist.tech/blog/ads1256-arduino-stm32-sourcecode

Regards, Dieter