High-Speed DSP and Analog System Design (eBook)

DR. THANH TRAN has over 25 years of experience in high‐speed DSP, computer and analog system design and is an engineering manager at Texas Instruments Incorporated. He currently holds 22 issued patents and has published more than 20 contributed articles. He is also an adjunct faculty member at Rice University where he teaches analog and digital embedded systems design courses. Tran received a BSEE degree from the University of Illinois at Urbana‐Champaign, Illinois in 1984 and Master of Electrical Engineering and Ph.D. in Electrical, Engineering degrees from the University of Houston, Houston, Texas in 1995 and 2001 respectively.

Preface 6
ACKNOWLEDGMENTS 8
Contents 9
About The Author 13
1 Challenges of DSP Systems Design 14
1.1 HIGH-SPEED DSP SYSTEMS OVERVIEW 15
1.2 CHALLENGES OF DSP AUDIO SYSTEM 18
1.3 CHALLENGES OF DSP VIDEO SYSTEM 19
1.4 CHALLENGES OF DSP COMMUNICATION SYSTEM 21
REFERENCES 24
2 Transmission Line (TL) Effects 25
2.1 TRANSMISSION LINE THEORY 26
2.2 PARALLEL TERMINATION SIMULATIONS 31
2.3 PRACTICAL CONSIDERATIONS OF TL 33
2.4 SIMULATIONS AND EXPERIMENTAL RESULTS OF TL 34
2.4.1 TL Without Load or Source Termination 34
2.4.2 TL with Series Source Termination 36
2.5 GROUND GRID EFFECTS ON TL 39
2.6 MINIMIZING TL EFFECTS 40
REFERENCES 42
3 Effects of Crosstalk 43
3.1 CURRENT RETURN PATHS 43
3.2 CROSSTALK CAUSED BY RADIATION 48
3.3 SUMMARY 53
REFERENCES 55
4 Power Supply Design Considerations 56
4.1 POWER SUPPLY ARCHITECTURES 56
4.2 DSP POWER SUPPLY ARCHITECTURAL CONSIDERATIONS 66
4.2.1 Power Sequencing Considerations 72
4.3 SUMMARY 75
REFERENCES 76
5 Power Supply Decoupling 77
5.1 POWER SUPPLY DECOUPLING TECHNIQUES 77
5.1.1 Capacitor characteristics 79
5.1.2 Inductor characteristics 82
5.1.3 Ferrite Bead Characteristics 84
5.1.4 General Rules-Of-Thumb Decoupling Method 85
5.1.5 Analytical Method of Decoupling 87
5.1.6 Placing Decoupling Capacitors 101
5.2 HIGH FREQUENCY NOISE ISOLATION 104
5.2.1 Pi Filter Design 105
5.2.2 T Filter Design 108
5.3 SUMMARY 112
REFERENCES 114
6 Phase-Locked Loop (PLL) 115
6.1 ANALOG PLL (APLL) 115
6.1.1 PLL Jitter 117
6.2 DIGITAL PLL (DPLL) 121
6.3 PLL ISOLATION TECHNIQUES 124
6.3.1 Pi and T Filters 124
6.3.2 Linear Voltage Regulator 128
6.4 SUMMARY 129
REFERENCES 130
7 Data Converter Overview 131
7.1 DSP SYSTEMS 131
7.2 ANALOG-TO-DIGITAL CONVERTER (ADC) 132
7.2.1 Sampling 134
7.2.2 Quantization Noise 136
7.3 DIGITAL-TO-ANALOG CONVERTER (DAC) 140
7.4 PRACTICAL DATA CONVERTER DESIGN CONSIDERATIONS 142
7.4.1 Resolution and Signal-to-Noise 143
7.4.2 Sampling Frequency 144
7.4.3 Input and Output Voltage Range 144
7.4.4 Differential Non-Linearity (DNL) 145
7.4.5 Integral Non-Linearity (INL) 147
7.5 SUMMARY 148
REFERENCES 150
8 Analog Filter Design 151
8.1 ANTI-ALIASING FILTERS 151
8.1.1 Passive and Active Filters Characteristics 152
8.1.2 Passive Filter Design 153
8.1.3 Active Filter Design 156
8.1.4 Operational Amplifier (op amp) Fundalmenta 157
8.1.4.1 Biasing Op Amps 160
8.1.5 DC and AC Coupled 165
8.1.6 First Order Active Filter Design 174
8.1.7 Second Order Active Filter Design 179
8.2 SUMMARY 185
REFERENCES 186
9 Memory Sub-System Design Considerations 187
9.1. DDR MEMORY OVERVIEW 187
9.1.1. DDR Write Cycle 189
9.1.2. DDR Read Cycle 191
9.2. DDR MEMORY SIGNAL INTEGRITY 191
9.3. DDR MEMORY SYSTEM DESIGN EXAMPLE 193
REFERENCES 196
10 Printed Circuit Board (PCB) Layout 197
10.1. PRINTED CIRCUIT BOARD (PCB) STACKUP 197
10.2. MICROSTRIP AND STRIPLINE 200
10.3. IMAGE PLANE 202
10.4. SUMMARY 203
REFERENCES 204
11 Electromagnetic Interference (EMI) 205
11.1. FCC PART 15B OVERVIEW 205
11.2. EMI FUNDAMENTALS 207
11.3. DIGITAL SIGNALS 209
11.4. CURRENT LOOPS 211
11.5. POWER SUPPLY 212
11.6. TRANSMISSION LINE 214
11.7. POWER AND GROUND PLANES 216
11.8. SUMMARY: EMI REDUCTION GUIDELINES 218
REFERENCES 220
Glossary 221
Index 223

"3 Effects of Crosstalk (p. 31-32)

In any electronic systems, it is not practical nor is it necessary to eliminate all the noise, as noise is not a problem until it interferes with the surrounding circuitries or radiates electromagnetic energy that exceeds FCC limits and or degrades the system performance. When noise interferes with other circuits it is called crosstalk.

Crosstalk can be transmitted through electromagnetic radiation or electrically coupling, such as when unwanted signals propagate on the power and ground planes or couple onto the adjacent circuits. One of the most challenging problems designers are facing in today’s electronic systems is to determine the source of crosstalk, especially in the case where crosstalk randomly causes system failures. Because components are so tightly packed into a very small printed circuit board (PCB). This chapter outlines the crosstalk mechanisms and design methodologies to minimize the effects of crosstalk.

3.1 CURRENT RETURN PATHS

In designing a system, it is crucial for designers to understand the current return paths as these current returns are the main sources of electromagnetically and electrically coupling. For example, the digital signal current return crosses the analog section of the design and causes noise on the analog waveforms or the current return generates a large current loop area which radiates onto the adjacent circuitries. Current returns follow different paths depending on their frequency.

A high frequency current flow tends to concentrate on the surface of the conductor as supposed to distribute uniformly across the conductor like a low frequency current. This phenomenon is known as skin effect and it modifies the current distribution and changes the resistance of the conductor. Due to skin effect, signals above 10 MHz tend to follow one return path while those below 10 MHz follow another.

The low-speed signal current returns on the path of least resistance, normally the shortest route back to the source as shown in Figure 3.2. In Figure 3.1, the high-speed signal current, on the other hand, returns on the path of least inductance, normally underneath the signal trace. Knowing the current return paths is important for designers to optimize the system design to reduce crosstalk."