Dash Cam based on the MT8735 Solution
Main functions:
(1) Product specifications: MT8735, 1080P 30FPS DVR, 3G/4G data background, electronic dog, IPS screen, front and rear dual recording, rear view camera, voice wake-up, voice operation.
(2) DVR recording: 1080P 30FPS high-definition video recording, no frame skipping or missing seconds, good night vision effect, real-time storage of driving images.
(3) Navigation: GPS+Beidou fast positioning, air-to-ground cold start time of 35 seconds, precise positioning, no external antenna required, support for multiple maps.
(4) Data: Real-time download of the latest driving safety data via 3G/4G, rapid provision of humanized services such as surrounding parking lots, gas stations, car services, rest areas, etc., and support for background service systems.
(5) Anti-theft recording: It has an anti-theft function when the engine is turned off, and can notify the owner immediately with 3G/4G data to prevent the car from being stolen.
(6) Intelligent Voice: Chat, tell stories, learn about the latest news, understand the stock market, and say goodbye to the days of playing with your phone while driving.
(7) Rearview Camera: Automatically switch when reversing, and you can easily switch between the front and rear camera images, taking into account both the front and rear cameras, and ensuring safety.
(8) Single TF card: One TF card can handle offline maps and video file storage, so you no longer have to spend extra money to buy an extra TF card.
(9) Wing Card Online: Don't worry if your car breaks down on Mount Everest, Wing Card Online can solve all your problems for you.
(10) UI Style: Car UI style, simple and easy to use.
(11) FM Transmitter: Used in conjunction with the car FM receiver, the rearview mirror sound effect is more pleasant.
(12) Bluetooth Hands-Free: After the owner's mobile phone is successfully paired with the host, it can easily answer calls and make voice calls, avoiding tickets and driving safer.
(13) Electronic Dog: Combined with GPS, it covers a wide range of data including traffic lights, speed cameras, gas stations, schools, toll booths, highway entrances, and service areas, ensuring accuracy and effectiveness.
(14) Other standard features: It has audio and video entertainment functions, supports the output of multiple audio and video formats, and supports 1080P high-definition video decoding.
Design Difficulties:
(1) The platform uses the MT8735 chip, which has many functions such as DVR and multimedia, GPS+Beidou, WIFI, Bluetooth hands-free (BT), radar electronic dog, FM transmitter, front camera, AVIN/CVBS rear camera, USB interface, LTE wireless communication, and a relatively high board density. It has many RF bands, such as 3-mode 8-band (also supports 5-mode 12-band China Mobile and China Unicom versions), and supports GSM/WCDMA/FDD-LTE (TD-SCDMA/TDD-LTE).
(2) Supported frequency bands GSM: 850/900/1800/1900, WCDMA: BAND1/8, FDD-LTE: BAND1/3/8/, (TD-SCDMA: BAND34/39) Our company has made a reasonable layout based on the board type to ensure signal integrity.
Our company's countermeasures:
(1) The board should be relatively small, and the RF part occupies a relatively large space. Each module should be covered with a shielding cover to avoid interference.
(2) RF signals should be kept as parallel as possible.
(3) Differential signals should be grounded on a strict 4-ply basis, and RF lines such as IQ lines should be grounded on a 4-ply basis.
(4) Due to the high design requirements for MTK platform chips, this project is strictly required to meet the manufacturer's approval.
(5) Design for Manufacturability (DFM) and Design for Assembly (DFA) tests.
Customer feedback:
The first version was successfully tested and put into mass production.
Design Highlights of TopBottom-Mounted DDR ICs
Design Difficulties:
1. Limited board space, four DDR chips occupy a large area.
2. DDR signal layer planning on the BGA side.
3. Three-level blind buried DDR address control signals require a T-type circuit.
Our Solutions:
1. DDR bottom-mounting and three-level blind buried circuit.
2. BGA component routing is divided into three circles: the outer circle uses the first layer closest to the device, the middle circle uses the second layer closest to the device, and the inner circle uses the third layer closest to the device.
3. DDR signals are fanned out on the pins, and address control signals are routed alternately across the three layers.
End Result:
The DDR layout occupies a small area, all signals have a ground reference, and the DDR signal simulation quality is excellent.