DDC232: Which Microcontroller for DDC232

Hi Khoi,

Sorry for slow reply but as Chen explained I was traveling... Anyhow, when you say 100+ sensors I guess you mean that you will need 3 or 4 DDC232, right?

As explained on the DS (start on pg 20), you can cascade them in daisy chain. There are different ways to do that and all work well. You can use MCU or FPGA. That doesn't matter and there is no ns critical timing specs (or jitter, etc...) so you can bitbang the GPIO of the MCU, for instance. Only thing is that it may have to be a "fast" MCU to do so at fast rates... Notice that the CLK and DCLK signals are on the 10-20MHz. Again, you can run them slower but make sure the device can finish all what needs to finish to meet the 500Hz...

Just FYI, if you don't know which mode to pick, I am thinking that at 500Hz you may be able to send all the data (100+ channels at 20bit) in the interval that goes from the DVALID to the CONV edge. Just ran the calcs. if so, that is the most forgiving approach from a layout/noise isolation perspective as the data transmission (and whatever toggling noise coming from that) happens at a different instant from the data conversion (from CONV to DVALID).

Regards,
Edu

Hi Khoi,

Sorry but just to make sure, when you say mux, you mean daisy chain 4 DDCs, right? I mean, I guess that you could just use a mux, i.e., connect the control signals to the first DDC, read it out, then connect to the 2nd DDC, read it out, etc... but that looks like unnecessary overhead to me. You can just do the daisy chain (output of one DDC into the input of the next) as explained on the DS. It'll save you a lot of traces and the mux component...

And I don't know much about the latest MCUs and their peripherals. I believe that most of our customers actually use small FPGAs. You can see the documentation of the DDC264 EVM for an example. But if you want to use an MCU, it is fine too. Again, just make sure you can deal with those clock rates. If you need help with MCU selection, you can post a question on the MCU e2e forum for that team to give you a recommendation or ask our FAE. Tell them to recommend something that can deal with ~20MHz serial rates.

Regards,

Eduardo

Hi Khoi,

• 232 will be the worst from power perspective (older device). DDC264 and DDC1128 are better and very similar between them, power-wise.
• 232 allows you to get 350pC in one shot while the others are limited to 150pC, but as your speed is low, if you really needed that range, you could choose to run the DDCs at 3x the speed to compensate for that (power would still be better than 232).
• From a density perspective, obviously each device gets better than its previous generation. Nevertheless, smaller is not always better (unless you are really space constrained), specially from a layout complexity, so, 1128 may be too much for you if all what you need is ~100 channels.
• From a price perspective, 232 is the most expensive (per channel), but there is no much difference between the 264 and 1128. On top of that, you would be paying but not using the left 28 channels on the 1128 (no technical issue though, just cost). So, 264 may be the most economic.
• Finally 1128 is protected under NDA. Not a big issue if you are willing to get one with us.. but I feel that you may not need as 264 may be the best solution.

Regards,

Edu