This thread has been locked.
If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.
We use 16bit 16ksps CODECs and have some problem when our central DSP inserts a "zero-signal" when squelching an audio input that have no sufficiant audio energy: that squelch is randomly causing our DAC to produce self oscillations in frequencies higher then the 16khz sampling of our system. We think it is the IIR instability for no-signal at the DAC, as the DAC has decimating post filter that may not designed to handle sero-signal conditions. Do anybody knows a work-around for this fenomenom, or a better CODEC DAC that is better behaved in this situation? Is gradual squelch helps? Is a "non-audio" tone injection may help?
What you experience is most likely the idle tone problem that is inherent to basic delta-sigma DACs. It is produced by the modulator for DC and very low frequency input data. TI has high performance delta sigma DACs that address this problem and have reduced or no idle tones.
Please take a look at the PCM17xx family or the PCM4104.
We are glad that we were able to resolve this issue, and will now proceed to close this thread.
If you have further questions related to this thread, you may click "Ask a related question" below. The newly created question will be automatically linked to this question.
In reply to Dominik Hartl11:
Can this sensitivity to low-frequency input can cause a persistant self-oscillations of 16 khz & up while the digital input to the DAC is hel at zero TDM?
In reply to uric:
Yes. Idle tone (digital input held at 0) can (and will) produce self-oscillations (in your case at 16kHz+) in sigma-delta DACs that don't have an idle-tone reduction mechanism (like internal dithering, which essentially always presents a non-DC signal to the DAC internally).
Thanks. Can you recommend some codcs that do not have this instability?
The PCM17xx family and the PCM4104 are examples that don't have this problem with idle tones.
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with respect to these materials. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.