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Problem of ADAU1401 working at 192kHz sampling rate

Question asked by 武帅兵 on Jan 23, 2015
Latest reply on Jan 26, 2015 by 武帅兵

Dear all,

  Now, I need EVAL-ADAU1401AEBZ to working at sampling rate of 192kHz. According to datasheets of ADAU1401 and UG-72, I set the PLL MODES,shown in Table 1. The waveforms of EXT oscillator is 3.3Vpp square waves, from Tektronix AFG3252.

MODESampling rateOscillator FrequencyMCLKIPLL MODE0PLL MODE0S3-2S3-3
196kHz24.675MHz (EXT Oscillator)Fs x 2560101
2192kHz49.152MHz (EXT Oscillator)Fs x 2560101
3192kHz12.288MHz (INT Oscillator)Fs x 640000
  In the three mode, I generated the 40kHz sine wave, the output waveforms are shown in Fig.1, Fig.2, and Fig.3, respectively. Obviously, the wavefrom is correct when ADAU1401 working at mode1, the wavefroms are erroneous in mode 2 and mode 3.
ADAU1401_Out40kHz_Osc24.576MHzSquare_SampleRate96kHz_PLL_Mode0is0_Mode1is1副本.jpg
Fig. 1. 40kHz waveform at mode 1
ADAU1401_Out40kHz_Osc49.152MHzSquare_SampleRate192kHz_PLL_Mode0is0_Mode1is1副本.jpg
Fig.2 40kHz waveform at mode 2
ADAU1401_Out40kHz_Osc12.288MHzSquare_SampleRate192kHz_PLL_Mode0is0_Mode1is0副本.jpg
Fig. 3 40kHz waveform at mode 3
     The problem is how the ADAU1401 works correctly at sampling rate of 192kHz ?
     Thanks,

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