in case of crash

There is no watchdog on the ADAU1701. If there is a crash, the device will need to be reset and initialized.

SigmaStudio generates code that is 100% deterministic and does not contain any program counter jumps (conditionals, jumps, branches), and the "Return to Start" operation is hardware based, not software based, the chances of the program crashing are extremely small (limited to memory corruption).

Message was edited by: BrettG. Changed "set" to "reset".

Thanks Brett.

I did encounter repeated crashes. It was apparently due to excessive radiated noise from a nearby switching supply. Of course, this had to be mitigated, but I believe in solving every problem twice if possible. I've also asked for the board to be relaid with a complete ground plane. Have you had other reports anything like this?

--Phil

Good layout practices are of key importance when dealing with a noisy system.

First of all, a solid ground plane is a necessity in order to maintain signal integrity and minimize EMI radiation. I have seen many customers experience severe EMI issues when trying to design a PCB with no ground plane. If you have two ground planes, I would recommend using stitching vias spead evenly throughout the board in order to connect them.

Power supply high frequency decoupling capacitors should be placed as close as possible to the respective power and ground pins, on the same side of the board as the SigmaDSP IC. There should be no vias between the pins and the decoupling caps. Please see the following excerpt from the ADAU144x datasheet for more detail.

Typically, we use a single 100 nF capacitor for each power-ground pin pair. However, if there is excessive high frequency noise in the system, an additional 10 nF capacitor can be used in parallel. In that case, the 10 nF capacitor should be closest, and the thermal connections should be on the far side of the 100 nF capacitor.

10 uF capacitors should be used for each named supply (DVDD, AVDD, IOVDD, etc) in order to provide a current reservoir in case of sudden current spikes.

The proximity of components to the IC is important. Here is my suggested order which should be followed when placing components. The top of the list begins with the components that should be placed closest to the IC, and the bottom of the list has the components that can be placed further away.

10 nF high frequency decoupling capacitors

100 nF high frequency decoupling capacitors

PLL filter components

Crystal

Current reservoir capacitors

Thanks Brett. I've sent the entire thread to PCB layout dept. and will review. --Phil

I'm working on a project with a fellow engineer who won't build anything without a watchdog timer. So he has his PIC microcontroller looking for a 1 Hz oscillator programmed in our ADAU1701, routed to a GPIO pin. If the PIC doesn't see it and times out, it resets both itself and the -1701.

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