Cirrus Logic AN168 - Manual (Page 2)

AN168
2 AN168REV2
TABLE OF CONTENTS
1. DESIGN PROCESS AND CONSIDERATIONS ........................................................................ 1
1.1 Design Flow ....................................................................................................................... 1
1.2 Mechanical Design ............................................................................................................. 4
1.2.1 Selecting the Acoustic Components ..................................................................... 4
1.2.1.1 Speaker Requirements ......................................................................... 4
1.2.1.2 Microphone Requirements .................................................................... 4
1.2.1.3 Speaker Housing Requirements ........................................................... 5
1.2.2 Placing the Speaker and Microphone ................................................................... 5
1.3 Electrical Design ................................................................................................................ 5
1.3.1 Selecting the Speaker Driver ................................................................................ 5
1.3.2 Setting the Speaker Driver Gain ........................................................................... 6
1.3.3 Volume Control ..................................................................................................... 7
1.3.4 Acoustic Coupling ................................................................................................. 8
1.3.5 Setting the Mic Preamp Gain ................................................................................ 8
1.3.6 Acoustic Sidetone ............................................................................................... 11
1.4 Echo Canceler Parameter Optimization ........................................................................... 11
1.4.1 Starting Example ................................................................................................. 11
1.4.2 Tweaking the Parameters ................................................................................... 12
1.4.3 Network Sidetone ................................................................................................ 13
1.4.4 Loop Gain ............................................................................................................ 14
1.5 Tests ................................................................................................................................ 14
1.5.1 Acoustic Coupling ............................................................................................... 15
1.5.1.1 Loop Gain Method ............................................................................... 15
1.5.1.2 Frequency Response Method ............................................................. 17
1.5.2 Acoustic Distortion .............................................................................................. 17
1.5.2.1 Frequency Sweep Test ....................................................................... 18
1.5.2.2 Buzz Test ............................................................................................ 18
1.5.3 Acoustic ERLE .................................................................................................... 19
1.5.3.1 White Noise RMS Method ................................................................... 19
1.5.3.2 Loop Gain Method ............................................................................... 20
1.5.4 Call Testing and Coefficient Optimization ........................................................... 23
1.5.4.1 Far-end single-talk counting ................................................................ 23
1.5.4.1.1 Subtest A, EC Convergence Test .............................................. 23
1.5.4.1.2 Subtest B, Half-Duplex to Full-Duplex transition time ................ 24
1.5.4.1.3 Subtest C, Transmit Suppression test ....................................... 24
1.5.4.2 Double-talk .......................................................................................... 24
1.5.4.3 Half-duplex alternate counting ............................................................ 25
1.6 Layout Guidelines ............................................................................................................ 25
1.6.1 CS6422-specific guidelines ................................................................................. 25
1.6.2 Car-Kit guidelines ................................................................................................ 26
1.6.2.1 +5VA/AGND Components ................................................................... 26
1.6.2.2 +5VD/DGND Components .................................................................. 26
1.6.2.3 +12VBATT/BATTGND Components ................................................... 27
1.7 Quick list of important points: ........................................................................................... 27
1.7.1 Reset and configuration timing ............................................................................ 27
1.7.2 Distortion ............................................................................................................. 27
1.7.3 Speaker/mic placement ....................................................................................... 27
1.7.4 Acoustic coupling ................................................................................................ 28
1.7.5 Training sequence ............................................................................................... 28
2. APPENDIX - EXAMPLE SPEAKER DRIVER CIRCUITS ...................................................... 29
2.1 Example 1: TDA1519A -- 15 Watts into 4 W .................................................................... 29
2.2 Example 2: TDA2003 -- 3 Watts into 4 W ........................................................................ 29
2.3 Example 3: TDA1905 -- 2.5 Watts into 4 W ..................................................................... 33
2.4 Example 4: LM1877-- 2 Watts into 4 W ........................................................................... 34
2.5 Example 5: LM4861-- 1 Watt into 4 W ............................................................................. 34