[Good book reading together - "Hardware Design Guide: From device recognition to mobile phone baseband design"] - Part 3

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[Good book reading together - "Hardware Design Guide: From device recognition to mobile phone baseband design"] - Part 3 [Copy link]

 

[Good book reading together - "Hardware Design Guide: From Device Cognition to Mobile Phone Baseband Design"]

--Part 3

Half a month has passed unknowingly. I have been busy welding prototypes and testing the project recently. Today I will share the contents of Chapters 4 to 6.

The title of Chapter 4 is Signal Integrity. What is integrity? How to maintain integrity during PCB design?

Signal Integrity (SI) is what we usually call signal quality. With the increase of signal rate, the transmission of digital signals can no longer only consider the logical implementation, but also how to enable the receiving device to receive the correct signal waveform. It sounds simple, signal integrity is a study of how to enable the signal to be correctly transmitted between the driver and the receiver. However, its content is very extensive, and with the development of electronics and communication technology, it continues to expand to other disciplines, including not only circuit and transmission line theory, but also electromagnetic field theory, and is also closely related to electromagnetic compatibility.

The so-called signal integrity generally includes two aspects: on the one hand, it studies the transmission of signals, that is, how to optimize the signal transmission path so that the chip at the receiving end can obtain the correct waveform; on the other hand, it studies the supply of power, that is, how to provide stable and low-noise power for the stable operation of the chip, that is, power integrity (SI).

Signal integrity in a broad sense refers to all problems caused by interconnects in circuit design. It mainly studies how the electrical characteristic parameters of interconnects affect product performance after interacting with the voltage and current waveforms of digital signals.

　　PCB signal integrity issues mainly include signal reflection, crosstalk, signal delay and timing error.

　　1. Reflection: When the signal is transmitted on the transmission line, when the characteristic impedance of the transmission line on the high-speed PCB does not match the source impedance or load impedance of the signal, the signal will be reflected, causing the signal waveform to overshoot, undershoot and the resulting ringing phenomenon. Overshoot refers to the first peak (or valley) of the signal jump, which is an additional voltage effect above the power supply level or below the reference ground level; undershoot refers to the next valley (or peak) of the signal jump. Excessive overshoot voltage often causes long-term impacts and damages the device, undershoot reduces the noise tolerance, and ringing increases the time required for the signal to stabilize, thereby affecting the system timing.

　　2. Crosstalk: In PCB, crosstalk refers to the unwanted noise interference caused by electromagnetic energy through mutual capacitance and mutual inductance coupling to adjacent transmission lines when the signal propagates on the transmission line. It is caused by the interaction of electromagnetic fields caused by different structures in the same area. Mutual capacitance induces coupling current, which is called capacitive crosstalk; while mutual inductance induces coupling voltage, which is called inductive crosstalk. On PCB, crosstalk is related to the length of the trace, the spacing between signal lines, and the condition of the reference ground plane.

　　3. Signal delay and timing error: The signal is transmitted at a limited speed on the wire of the PCB. There is a transmission delay between the signal from the driver end to the receiver end. Excessive signal delay or mismatched signal delay may lead to timing errors and confusion of logic device functions.

　　Signal integrity analysis is to apply the traditional theories of circuits, transmission lines, electromagnetics, signals and systems to solve the problems caused by interconnection lines in the above circuit design. To put it more bluntly, signal integrity is the study of how to make the signal sent by the driver chip pass through the transmission channel and be correctly received by the receiving chip.

To better ensure signal integrity during the PCB design process, the following aspects can be considered.

(1) Circuit design considerations. These include controlling the number of synchronously switched outputs, controlling the maximum edge rate (dI/dt and dV/dt) of each unit, and obtaining the lowest acceptable edge rate; selecting differential signals for high-output functional blocks (such as clock drivers); and terminating passive components (such as resistors, capacitors, etc.) on the transmission line to achieve impedance matching between the transmission line and the load.

(2) Minimize the trace length of parallel wiring.

(3) Components should be placed away from I/O interconnect interfaces and other areas susceptible to interference and coupling, and the spacing between components should be minimized.

(4) Shorten the distance between the signal trace and the reference plane.

(5) Reduce trace impedance and signal drive level.

(6) Terminal matching. Terminal matching circuits or matching elements can be added.

(7) Avoid parallel routing and provide sufficient spacing between routing lines to reduce inductive coupling.

The title of Chapter 5 is Hardware Design of Mobile Phone Baseband (A Letter from Home is Worth a Thousand Pieces of Gold), and the content of this part is biased towards practical applications.

Mobile phones are the most common terminal devices in our daily lives. Most people only know the parameters on paper. The book introduces us to what is the mobile phone baseband, lithium battery and its protection, sorts out the power architecture, introduces us to the charging principle of mobile phones, as well as PDN, camera and screen interface, audio interface, sensor, briefly describes SIM card, and popularizes some basic knowledge of EMC. Let's learn these contents one by one.

Introduction to mobile phone baseband, what is baseband? There are two very key chips in the mobile phone, one is AP (Application Processor) and the other is BP (Baseband Processor). The baseband chip determines what kind of network our mobile phone supports, such as GSM, CDMA, WCDMA, TD-SCDMA, etc., which are all determined by it. With the development of technology, AP and BP are concentrated together. In the field of communication, the frequency band (frequency bandwidth) inherent in the original signal sent by the information source, that is, the transmitting terminal without modulation (spectrum shifting), is referred to as baseband.

Below is the content of the book, I'll post the pictures.

Mobile phones are very special products. Simply put, they are composed of several components: main control logic circuit + power management + radio frequency circuit + display module + peripheral interface circuit. Here we focus on the power management module. Mobile phones are not like computers that need to be plugged in at any time. The scenarios in which we use mobile phones are more complicated, so there must be higher requirements for the battery capacity and charging power of mobile phones.

The book contains a lot of text to explain the relevant knowledge of lithium batteries and their charging and discharging protection principles, and also introduces us to a fast charging solution. The following is all the content introduced in this chapter: Chapter 5

5.1 Introduction to Mobile Phone Baseband

5.2 Lithium Batteries and Their Protection

5.2.1 Introduction to lithium battery parameters

5.2.2 Lithium battery discharge undervoltage protection UVP principle

5.2.3 Lithium battery discharge overcurrent protection OCD principle

5.3 Power supply architecture review

5.4 Very important Power Path: Power Path

5.5 Mobile Phone Charging Principle

5.5.1 Mobile Phone Charging and Discharging Architecture

5.5.2 Mobile phone charging process

5.5.3 Introduction to a fast charging solution

5.6PDN and its optimization

5.6.1 PDN Concept

5.6.2 PDN DC simulation and optimization direction

5.6.3 PDN AC Simulation and Optimization Direction

5.7 Camera and Screen Interface

5.7.1 Camera Interface

5.7.2 Screen Interface

5. 7.3 MIPI D-PHY

5. 7.4 MIPI C-PHY

5.7.5 MIPI Switch Introduction

5.8 Audio Interface

5.8.1 Headphones and USB Path

5.8.2 Speaker drive circuit

5.9 Sensors

5.9.1 Gyroscope, Accelerometer, and Magnetometer

5.9.2 Infrared and Flash

5.9.3 Light and distance perception

5.9.4 Motor vibrator

5.10 SIM Card Overview

5.11 EMC Basics

5.11.1 Electrostatic coupling and magnetic field coupling

5.11.2 Antenna Effect Electromagnetic Coupling

5.11.3 Differential-mode interference and common-mode interference

5.12 Mobile Phone Design Practical Case Study

5.12.1 Practical Explanation: Five PCB Layout Strategies

5.12.2 Practical explanation: Key points of capacitor layout for DCDC switching power supply

5.12.3 Practical explanation: Camera interference analysis and solutions

5.12.4 Practical explanation: Analog circuit routing strategy, why is there a main ground?

5.12.5 Practical explanation: The impact of EMC capacitors on mobile phone serial ports

5.12.6 Practical Explanation: MIPI C-PHY Rectification Case

5.12.7 Practical explanation: the famous TDMA noise

5.12.8 Practical explanation: leakage analysis process

5. 12.9 Practical explanation: Common analysis and maintenance ideas

5.12.10 Practical explanation: The "roast chicken method" of current injection short circuit analysis

5.12.11 Practical explanation: Mobile phone power consumption optimization

5.12.12 Practical explanation: Reasons for inaccurate power measurement and power jumps

5.12.13 Practical explanation: Introduction to the mobile phone development process

There is too much content in this part, and I am still learning it myself. As for the knowledge related to antennas, I have recently tested the performance of our customized Lora antennas in the laboratory during my study (mainly S11, S22, SWR). If you are interested, you can learn more about it. The knowledge in the book is the experience accumulated by the masters. I feel very benefited after reading it. I really hope that I can know everything now.

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Chapter 6 is titled Test Instrumentation and Board-Level Testing

The following is the table of contents. The book not only teaches us how to use a multimeter and an oscilloscope, but also lists some problems that may be encountered during use and summarizes relevant experiences for us, which is very useful. For some novices, I also had these confusions when I first started working, but fortunately, my master patiently explained them to me, and now I feel very familiar with some of the contents in the book. For the use of instruments, the fastest way to learn is to do it yourself. It is best to have someone teach you. If not, go to the Internet to find a tutorial, then explore it yourself, get a board to test it, and toss it back and forth a few times, and the instrument will naturally be used.

That’s all for this book! This is my first time participating in a review, and I know that I have many shortcomings. I will grow slowly! Come on, future senior engineers!!!

秦天qintian0303

Mobile phones are the most common terminal devices in our daily lives, but many baseband patents are in the hands of a few companies.

ying20240715

Qintianqintian0303 posted on 2024-9-23 12:50 Mobile phones are the most common terminal devices in our daily lives, but many baseband patents are in the hands of a few companies.

This is where our senior engineers come in.