In recent years, a wide variety of in-vehicle applications have been implemented in automobiles, and the amount of data handled is rapidly increasing.
In applications that handle video data, even if we limit ourselves to vehicle-mounted cameras, there are two trending demands: "higher image quality" and "an increase in the number of cameras installed per vehicle."
Additionally, there has been a rapid rise in the number of in-vehicle infotainment displays, higher resolution displays, and an increase in applications for advanced driver assistance systems (ADAS), such as E-mirror, driver status monitors, parking assist systems, and drive recorders. The demand for more applications that transmit video data and higher resolution displays is also increasing.
For those who have these issues, we recommend GMSL SerDes ICs from Maxim Integrated, formerly known as Maxim, which was integrated into Analog Devices (ADI).
Here we will introduce the features of ADI 's (Maxim) GMSL SerDes ICs.
What are SerDes
SerDes is an acronym of Serializer and De-serializer, and generally refers to ICs that perform high-speed serial transmission. More than 10 years ago, when the resolution handled was SD (Standard Definition), such as VGA or NTSC equivalent transmission, parallel 8-bit digital transmission was sufficient.
However, in recent years, as the required resolution has increased to HD (High Definition, 1280 x 720), Full-HD (1920 x 1080), and 4K2K, it has become difficult to transmit digital data in parallel. As the number of parallel bits increases, various constraints have arisen, such as board area, cable shape, and long wiring. In addition, increasing the transmission rate (clock frequency) has made it increasingly difficult to ensure timing constraints (setup / hold), and has made design more difficult.
This is why SerDes ICs were developed.
Since data is transmitted serially between the serializer and deserializer, large amounts of high-resolution video data can be transmitted without consuming board area or cable space. In addition, the Clock Embedded method, which embeds the clock in the serial transmission data and transmits it, solves the problem of timing constraints (setup / hold).
We believe that SerDes will continue to be an indispensable technical element in applications that transmit high-resolution data between devices.
What is GMSL
GMSL is a low-power, ... ADI) Maxim Integrated (Maxim Gigabit Multimedia Serial Link developed by SerDes IC A general term for the old Maxim The company 2003 In 2016, we were the first to GMSL SerDes IC Since then, about 20 It has been leading the industry for years.
GMSL SerDes IC The main features of this product are as follows.
・Longest 15m Coaxial (Coax) Cable or STP (Transmission possible via shielded twisted pair cable
・ GMSL Interoperability of serializers and deserializers allows different interfaces to be used at each end of the link
・ GMSL Link diagnostic function (Short to Battery, Short to GND, OPEN detection)
- Spread spectrum capability improves the electromagnetic interference (EMI) performance of SerDes links
Different interfaces can be used at each end of the link
The GMSL serializer IC receiver and GMSL deserializer IC transmitter are available with a variety of interfaces, making it possible to connect a variety of ICs/ systems via the GMSL link.
■ Serializer product selection guide
model number |
input |
interface |
Speed (Mbps) |
Size (mm2) |
HDCP |
application |
MAX96707 |
14 |
CMOS/LVCMOS |
1740 |
16.8 |
|
1.7Gbps compact camera |
MAX96709 |
14 |
CMOS/LVCMOS |
1740 |
16.8 |
|
|
MAX96705 |
16 |
CMOS/LVCMOS |
1740 |
26 |
|
|
MAX96711 |
14 |
CMOS/LVCMOS |
1740 |
26 |
|
|
MAX9271 |
16 |
CMOS/LVCMOS |
1500 |
26 |
|
1.5Gbps camera/display |
MAX9273 |
22 |
CMOS/LVCMOS |
1500 |
37.2 |
|
|
MAX9249 |
4 |
LVDS |
2500 |
50.4 |
|
2.5Gbps camera/display |
MAX9259 |
30 |
CML |
2500 |
65.6 |
|
|
MAX9293 |
ー |
HDMI |
3120 |
65.6 |
〇 |
3.12Gbps display |
MAX9277 |
4 |
LVDS |
2800 |
50.4 |
|
|
MAX9281 |
4 |
LVDS |
2800 |
50.4 |
〇 |
|
MAX9275 |
30 |
LVCMOS |
2800 |
65.6 |
|
|
MAX9279 |
30 |
LVCMOS |
2800 |
65.6 |
|
|
MAX9291 |
ー |
HDMI |
3120 |
65.6 |
|
■ Deserializer Product Selection Guide
model number |
input |
interface |
Speed (Mbps) |
Size (mm2) |
HDCP |
application |
MAX96706 |
14 |
CMOS/LVCMOS |
1740 |
26 |
|
1.7Gbps compact camera |
MAX96708 |
14 |
CMOS/LVCMOS |
1740 |
26 |
|
|
MAX9272A |
28 |
CMOS/LVCMOS |
1500 |
50.4 |
|
1.5Gbps camera/display |
MAX9264 |
30 |
CMOS/LVCMOS |
2500 |
65.6 |
〇 |
2.5Gbps camera/display |
MAX9268 |
4 |
LVDS |
2500 |
50.4 |
|
|
MAX9260 |
30 |
CMOS/LVCMOS |
2500 |
65.6 |
|
|
MAX9278A |
4 |
LVDS |
3120 |
50.4 |
|
3.12Gbps display |
MAX9282A |
4 |
LVDS |
3120 |
50.4 |
〇 |
|
MAX9276A |
32 |
CMOS/LVCMOS |
3120 |
65.6 |
|
|
MAX9280A |
32 |
CMOS/LVCMOS |
3120 |
65.6 |
〇 |
|
MAX9288 |
4 |
CSI-2 |
3120 |
50.4 |
|
|
MAX9278A |
4 |
LVDS |
3120 |
50.4 |
|
|
MAX9286 |
4 |
CSI-2 |
1500 |
65.6 |
|
Quad SER input for camera |
As you can see, we have GMSL SerDes ICs with a variety of interfaces, including CMOS/LVCMOS, LVDS, HDMI, MIPI CSI-2, etc. We also have a wide range of other GMSL products, so please feel free to contact us.
GMSL link diagnostic function (Short to Battery, Short to GND, OPEN detection)
Some GMSL ICs have a GMSL link diagnostic function (line fault detection) built in. By adding an external resistor network between the GMSL link and the LMN0/LMN1 pins and including a reference voltage in the range of 1.5V to 1.7V, the system can automatically detect the physical status of the GMSL link.
An optional hardware pin (LFLTB/GPIO1) can be used to flag any OPEN detection (cable break), Short to Battery, or Short to GND. Two line fault monitor pins (LMN0 and LMN1) are built in and can be used with coaxial and shielded twisted pair (STP) cables.
The normal operating threshold of the LMN0/LMN1 pin is 0.57V to 1.07V. If the cable is shorted to GND, the line voltage drops below this threshold. If the cable is open, the line voltage rises to the reference voltage, which can range from 1.5V to 1.7V. If the cable is shorted to the battery, the line voltage rises above 2.5V.
Spread spectrum function
The GMSL SerDes IC has a spread spectrum function. This can improve the electromagnetic interference (EMI) performance of the GMSL link.
Here is the PIXEL CLOCK FREQUENCY graph when using the spread spectrum function setting and spread spectrum described in the data sheet of the GMSL serializer product "MAX96707".
To use the spread spectrum function with the “MAX96707”, set a dedicated register (SS register).
SS |
Spread (%) |
000 |
Power-up default (no spread spectrum) |
001 |
±0.5% spread spectrum |
010 |
±1.5% spread spectrum |
011 |
±2% spread spectrum |
100 |
No spread spectrum |
101 |
±1% spread spectrum |
110 |
±3% spread spectrum |
111 |
±4% spread spectrum |
By setting the SS register, energy is prevented from concentrating on a specific frequency of the pixel clock. Also, by manually setting the SDIV register, the user can set the modulation frequency (usually 20kHz) according to the PCLKIN frequency. This makes it possible to mitigate energy concentration on a specific frequency that may cause electromagnetic interference (EMI).
Please refer to the data sheet for details on how to set up.
In this article, we introduced ADI (Maxim) 's GMSL SerDes ICs that are ideal for solving problems for those designing automotive applications. Evaluation boards for each device introduced are available. Please feel free to contact us.
Application example
・ADAS (Advanced Driver Assistance System)
Infotainment
Click here to purchase products
Click here for manufacturer site/other related links
- Gigabit Multimedia Serial Link (GMSL) SerDes IC
- MAX96707 (Datasheets can be downloaded here)
- MAX96706 (Datasheets can be downloaded here)
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