高通手机PCB Layout Guidelines

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1 Introduction...................................................................................................... 6
1.1 Purpose and intended audience..................................................................................... 6
1.2 Documentation overview.............................................................................................. 6
1.3 Terms and acronyms ..................................................................................................... 8
2 Layout Strategy ............................................................................................... 9
2.1 Parts placement and signal flow ................................................................................... 9
2.2 Shielding ..................................................................................................................... 12
2.3 PCB stack-up .............................................................................................................. 14
2.4 Using vias ................................................................................................................... 14
2.5 Grounding ................................................................................................................... 15
3 PCB Considerations...................................................................................... 16
3.1 Number of layers and PCB stack-up........................................................................... 16
3.2 Assigning functions to each layer ............................................................................... 17
3.3 RF traces: controlled-impedance transmission lines................................................... 18
3.3.1 Example microstrip design................................................................................ 19
3.3.2 Example stripline design ................................................................................... 20
3.4 Vias ............................................................................................................................. 21
3.5 Grounding ................................................................................................................... 23
3.6 Component land patterns ............................................................................................ 24
4 Example Reference Design........................................................................... 25
4.1 High-level layout concept ........................................................................................... 25
4.2 Stack-up and layer descriptions .................................................................................. 27
4.2.1 Layer 1 description............................................................................................ 27
4.2.2 Layer 2 description............................................................................................ 28
4.2.3 Layer 3 description............................................................................................ 30
4.2.4 Layer 4 description............................................................................................ 32
4.2.5 Layer 5 description............................................................................................ 32
4.2.6 Layer 6 description............................................................................................ 33
5 Specific Layout Guidelines........................................................................... 34
5.1 RF signals ................................................................................................................... 34
5.1.1 General RF guidelines ....................................................................................... 34
Fundamentals of PCB Layout Guidelines for radioOne® Designs Application Note Contents
80-V9813-1 Rev. A 3 QUALCOMM Proprietary
5.1.2 Clearing ground below RF traces and pads....................................................... 36
5.1.3 GPS circuits and signals .................................................................................... 36
5.1.4 Front-end circuits and signals............................................................................ 37
5.1.5 RFIC matching networks................................................................................... 38
5.2 LO-related circuits and signals ................................................................................... 40
5.2.1 LO signals (at UHF) .......................................................................................... 40
5.2.2 VCO tuning lines............................................................................................... 41
5.2.3 TCXO distribution............................................................................................. 42
5.3 Baseband Rx and Tx signals ....................................................................................... 43
5.4 Digital signal traces .................................................................................................... 44
5.4.1 PDM signals: TX_AGC_ADJ and TRK_LO_ADJ........................................... 44
5.4.2 SBI signals......................................................................................................... 44
5.4.3 Other digital signals........................................................................................... 45
5.5 DC power.................................................................................................................... 46
5.5.1 PA power supply distribution............................................................................ 46
5.5.2 Power supply traces routed under RFICs .......................................................... 47
6 Other Board-level Considerations ............................................................... 49
6.1 Radiated desensitization.............................................................................................. 49
6.1.1 Desensitization due to the CHIPx16 45th harmonic .......................................... 49
6.1.2 Desensitization due to the TCXO 46th harmonic............................................... 50
6.1.3 Desensitization due to LCD and camera interface ............................................ 53
6.2 GPS functions ............................................................................................................. 54
6.3 Thermal considerations............................................................................................... 54
7 Layout Checklist............................................................................................ 56

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