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ADAU1701 Selfboot Problem

Question asked by freemanc on Aug 28, 2013
Latest reply on Oct 18, 2013 by freemanc

Hi Everyone,

 

I need your help please!  I am busy with a design using the ADAU1701.  I have bought the evaluation kit and as a test program just output a 500Hz tone to all 4 DACs.  The program works just fine on the evaluation board, but not on my design.  The design I have is the following attached schematic, I've removed the non-DSP related parts to reduce complication in explanation.

  

The speaker impedance is 42 Ohm, little headphone driver, connected directly to VOUT1 on IC3.  WP is manually pulled low when I want to program the EEPROM, thereafter released to be pulled high by R10.  Thereafter I manually set Selfboot to PVDD before powering on again.  I have checked the EEPROM with Sigma Studio and the identical program that was loaded to the evaluation kit is in my EEPROM (IC4).  I suspected the reset was being pulled high too fast so soldered in a 10uF capacitor in parallel with C9, this now takes a good half a second or so to fully charge, and it is very clean.  Once the DSP is powered up, there is activity on the SDA and SCL lines, but for some reason there is no tone played over the speaker!  DVDD is sitting at approximately 1.8V.  The OSCO Pin has an 11.2MHz sine signal on it (using crystal AM-11.2896MAGQ-T from TXC Corporation), so it appears the device is being clocked.

 

What could be wrong?

 

Kind regards

Charles

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