FPGA based UNIPI system

[moodz]

Hi Moodz,

Given the price of the AD7760, I've been having a look for suitable alternatives for direct sampling and think the following may be quite decent - I've got one on order to play with, just need to knock up a test PCB.

https://www.akm.com/global/en/produc...-adc/ak5578en/

Quite reasonably priced (Around £16 from Digikey), it has the facility to combine all 8 channels and improve SNR and dynamic range accordingly.
There are also 4 and 2 channel versions available at lower prices.

The sample rate is up to 768kHz at 32-bits, so not as high as the 2.5MHz of the AD7760 but the claimed dynamic range of 130dB (in 8 to 1 mode) is mighty impressive. Whether that is achievable at 768kHz sample rate remains to be seen.

Cheers

Looks like a nice chip ... the AD7760 is strange ... the Eval board all built up and tested is only a few dollars more than the one off chip price ??? Be interesting to see what you can make of the AK5578.
I was tempted to move away from the FPGA to a CPU ... but will stick with the FPGA now as it can deal better with weird timing issues that seem to crop up with the ADCs. Besides the FPGA makes for a nice multichannel realtime builtin oscillscope and logic probe which is invaluable for debugging the DSP and ADC logic. I am ordering some FPGA boards from china to replace my obsolete boards but the VHDL code will be the same.
If you are making a board for the AK5578 then I would also be interested as the 2.5 MSPS that the AS7760 offers is nice ... but prob not necessary.

moodz.

[Olly]

Looks like a nice chip ... the AD7760 is strange ... the Eval board all built up and tested is only a few dollars more than the one off chip price ??? Be interesting to see what you can make of the AK5578.
I was tempted to move away from the FPGA to a CPU ... but will stick with the FPGA now as it can deal better with weird timing issues that seem to crop up with the ADCs. Besides the FPGA makes for a nice multichannel realtime builtin oscillscope and logic probe which is invaluable for debugging the DSP and ADC logic. I am ordering some FPGA boards from china to replace my obsolete boards but the VHDL code will be the same.
If you are making a board for the AK5578 then I would also be interested as the 2.5 MSPS that the AS7760 offers is nice ... but prob not necessary.

moodz.

I'll probably use the Raspberry Pi Pico 2 as the controller for the AK5578 and try to get the I2S interface to the chip implemented in its programmable PIO so that I can leave the cores free for processing.

Busy creating the Kicad part symbol for the AK5578 now, then will put a schematic and PCB together with it and the Pico so I can evaluate it. Will let you know how I get on.

I kind of agree with you about the FPGA, it's really nice for development with all the great debug features and I'm glad I've got one to use in the lab - it's just a bit pricey to use in a production model.

Olly