DVDD regulator layout, ADAU145x (trace lengths)

Hello Joe42,

No, there is no abnormal sensitivity to the trace length of that signal. 2-3 inches should be fine. However, make sure the 100nf caps for the IOVDD and the DVDD are very close to the pins. The other larger caps can be over with the transistor.

I would also take a look at traces that run close to these traces to make sure you avoid any coupling of digital signals onto the power rails. Move them further away or place guard traces around them.

Thanks,

Dave T

Thanks, Dave. One related question, if I may:

I see that during reset or idle, DVDD can draw 95mA, which is a lot of power for standby. To prevent damage, I leave IOVDD on during standby (since the microcontroller is always on, and I2C is active). Instead of IOVDD, can I instead feed DVDD from the same 3.3V source as PVDD and AVDD? (AVDD/PVDD is fed through a ferrite). I can't think of a reason this wouldn't work, but just making sure.

Hello Joe,

My only worry is that noise from the internal digital circuits on the DVDD power would get into the AVDD or the PVDD. Both of those supplies need to be quite. If I were to choose I would say the PVDD is the most important since the performance of the PLL is important. So if you were to run it on the AVDD then make sure you isolate (decouple) the two supplies. Also keep in mind you will be performing a reset by doing this. So you will need to reprogram the part.

So I think this will work for you. I don't see a problem otherwise.

Dave T

Thanks! Are using the usual ferrites (similar to EVB) enough decoupling, in your opinion? I may play it safe and just add another little regulator.