Burr Brown PCM1738 - 24-Bit, 192kHz Sampling.pdf - MaxDat

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CONSIDERATIONS FORAPPLICATIONS CIRCUITSPCB LAYOUT GUIDELINESA typical PCB floor plan for the PCM1738 is shown inFigure 14. A ground plane is recommended, with the analogand digital sections being isolated from one another using asplit or cut in the circuit board. The PCM1738 should beoriented with the digital I/O pins facing the ground planesplit/cut to allow for short, direct connections to the digitalaudio interface and control signals originating from thedigital section of the board.Separate power supplies are recommended for the digitaland analog sections of the board. This prevents the switchingnoise present on the digital supply from contaminating theanalog power supply and degrading the dynamic performanceof the DACs. In cases where a common +5V supplymust be used for the analog and digital sections, an inductance(RF choke, ferrite bead) should be placed between theanalog and digital +5V supply connections to avoid couplingof the digital switching noise into the analog circuitry.Figure 15 shows the recommended approach for singlesupplyapplications.Digital PowerAnalog Power+V D DGNDAGND +5VA+V S–V SREGV CCDigital LogicandAudioProcessorV DDDGNDPCM1738AGNDOutputCircuitsDigitalGroundDIGITAL SECTIONANALOG SECTIONAnalogGroundReturn Path for Digital SignalsFIGURE 14. Recommended PCB Layout.Power SuppliesRF Choke or Ferrite Bead+5V AGND +V S–V SREGV DDV CCV DDDGNDPCM1738OutputCircuitsDIGITAL SECTIONAGNDANALOG SECTIONCommonGroundFIGURE 15. Single-Supply PCB Layout.30PCM1738SBAS174A
1/4f S or 1/8f SWDCKBCKAudio Data Word = 16 BitDATALDATAR15 16 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16MSBLSBAudio Data Word = 20 BitDATALDATAR19 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20MSBLSBAudio Data Word = 24 BitDATALDATAR23 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24MSBLSBFIGURE 16. Audio Data Input Format for External Digital Filter (Internal DF Bypass Mode) Application.WDCK50% of V DDt BCH t BCL t LBBCK50% of V DDt BCYt BLDATALDATAR50% of V DDt DSt DHSYMBOL PARAMETER MIN MAX UNITSt BCY BCK Pulse Cycle Time 18 nst BCL BCK Pulse Width LOW 7 nst BCH BCK Pulse Width HIGH 7 nst BL BCK Rising Edge to WDCK Falling Edge 5 nst LB WDCK Falling Edge to BCKIN Rising Edge 5 nst DS DATA Set-Up Time 5 nst DH DATA Hold Time 5 nsFIGURE 17. Audio Interface Timing for External Digital Filter (Internal DF Bypass Mode) Application.BYPASS AND DECOUPLING CAPACITORREQUIREMENTSVarious sized decoupling capacitors can be used, with nospecial tolerances being required. All capacitors should belocated as close as physically possible to the power supplyand reference pins of the PCM1738 to reduce noise pickupfrom surrounding circuitry. Aluminum electrolytic capacitorsthat are designed for hi-fi audio applications are recommendedfor larger values, while metal-film or monolithicceramic capacitors are recommended for smaller values.I/V SECTIONI/V conversion, using the circuit shown in Figure 9, achievesdata-sheet performance (see Figure 9). To obtain 0.0005%THD+N, 117dB signal-to-noise ratio audio performance, THD+Nand input noise performance an op amp IC must be considered.Input noise of the op amp directly effects the output noise levelof the application.All components of the I/V section should be located physicallyclose to the PCM1738 current outputs. All connectionsshould be made as short as possible to eliminate pickup ofradiated noise.POST LOW-PASS FILTER DESIGNThe out-of-band noise level and sampling spectrum level aremuch lower than typical delta-sigma type DACs, due to thecombination of a high-performance digital filer and theadvanced segment DAC architecture. The use of a secondorthird-order filter is recommended for the post low-passfilter (see Figure 9 for a second-order filter) following the I/V conversion stage. The cutoff frequency of the post LPF isdependent upon the application, given the variety of samplingrates supported by the CD-DA, DVD-M, DVD-A, andSACD systems.PCM1738 31SBAS174A
Page 2 and 3: SPECIFICATIONSAll specifications at
Page 4 and 5: V CC 1BLOCK DIAGRAMLRCKDATABCKInput
Page 6 and 7: TYPICAL PERFORMANCE CURVES (Cont.)A
Page 8 and 9: TYPICAL PERFORMANCE CURVES (Cont.)A
Page 10 and 11: ANALOG FIR FILTER PERFORMANCE FOR D
Page 12 and 13: t RSTReset Reset RemovalV DD2.4V/ma
Page 14 and 15: LRCK50% of V DDt BCH t BCL t LBBCK5
Page 16 and 17: MODE CONTROL REGISTERSUser-Programm
Page 18 and 19: REGISTER 18 (Cont.)FMT[2:0] Audio I
Page 20 and 21: REGISTER 19 (Cont.)FLTDigital Filte
Page 22 and 23: B15 B14 B13 B12 B11 B10 B9 B8 B7 B6
Page 24 and 25: APPLICATION FOR EXTERNAL DIGITAL FI
Page 26 and 27: APPLICATION FOR DSD FORMAT (DSD MOD
Page 28 and 29: APPLICATION FOR MONAURAL MODE OPERA
Page 32: IMPORTANT NOTICETexas Instruments a

Burr Brown PCM1738 - 24-Bit, 192kHz Sampling.pdf - MaxDat

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