ADAU1701 - Overvoltage Problem

Hi,

Haven't had this misfortune yet with SigmaDSP, but I've blown a ARM processor with a 3.3V regulator shorted input to output. With an absolute max rating of 4.0V, it's likely the -1701 is toast. However, your desire to confirm the diagnosis in the face of some serious "surgery" makes good sense. In addition to measuring the 1.8V regulator, perhaps you can try a few additional tests:

Measure the DC bias on the DAC inputs and ADC outputs, which normally the IC maintains at about 1.6V.

Bring the antenna of a portable radio tuned to FM 98.3 MHz near the suspect IC. This is the second harmonic of the MIPS frequency, where a working IC (programmed or not) makes just enough signal to quiet a radio at close range (compare to the results with a known good board).

A negative result on either test indicates a bad IC, though the converse may not be true.

Assuming the IC is bad, removing it from your board is quite possible. Where I work our repair persons use a small heat gun in the 200 watt range with a narrow nozzle. Typically they would apply flux to the pins. Then apply heat, as the chip reaches soldering temperature, lift a corner with a dental pick. As with any surgery, experience helps (try it with any SMT parts on junk boards first).

Tube amps do rock! Funny how us audio folks are fond of both tubes and DSP.

Bob

Bob - Thanks for the helpful info!

I did find about 1/2 the DC bias mentioned ant both DAC and ADC.

That was enough encouragement for me, so next step is swapping the dsp.

I will keep you posted just fyi.

Thank you again!

Mike

Leary of the heat gun method... as I have used in the past to remove large quantities of parts for recycle.

I constructed a square tip made from a 1" length of 3/8" copper plumbing supply tube that fits on my Weller iron.

It worked fantastic and perfectly removed the IC in about 3 seconds!

However... after reinstalling a new IC the board still did not work, so I must have more problems than just the IC.

I do have better dc bias at some of the analog i/o, but still not causing fm radio interference like a working chip does (Brilliant Trick). I do see the crystal @ 12 mhz on the scope and 1.8 regulation is functioning properly.

Back to the drawing board

Hello Mike,

I really like your removal method! Could I ask you to post the details of how you made your tool and/or a photo? It would be helpful to me and others.

Since you're getting crystal but no MIPS, one place to look at is the PLL components and connections at pins 33-35, 38, and 39. Something may have been damaged there.

Bob

Once an IC has been pushed beyond its limits I would usually cut my losses and change it like you have done. It's difficult if not impossible to know what kind of internal damage has been incurred.

Are you still getting your "Compiled, Comms Failed" error after changing your chip? I spent a while getting my ADAU170xEBZ evaluation board to program before I moved my USB programming cable to a different USB port which appeared to solve the problem.

Also, on page 17 of the datasheet, under initialisation. It states that you need to :

"Turn off the default muting of the converters, clear the data registers, and initialize the DAC setup register (see the Control Registers Setup section for specific settings)."

This is after you have programmed the chip.

I see the section in the datasheet that states "

The default boot ROM program copies audio from the inputs to the outputs without processing it".

Are you feeding in serial digital audio?

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Thank you,
EZ Admin