Views: 0 Author: Site Editor Publish Time: 2023-10-25 Origin: Site
With the development trend of high intensification and ultra-high data rate of electronic products, when functionality is continuously realized and improved, its maximum stability and reliability will inevitably be considered. Multi-function, high speed and stability, reliability and security are a contradiction. Discuss the electrostatic protection devices currently used on high-speed data interface lines!
FireWire ---Formerly known as IEEE 1394, is a high-performance serial bus
Display I/O---Bus
SATA II ---Stands for Serial ATA
HDMI--- High-definition multimedia interface (1.966GBd / 2.7GBd / 3.0GBd / 3.4GBd)
Terminology:
Rdiff: Differential series resistance
VBR: Breakdown voltage (IBR = 1mA typical)
VRwm: maximum reverse working voltage
VCL: Clamping voltage
VFC: Forward clamping voltage
IPP: Peak current (8/20µS typical)
(a) Unidirectionality
Single ESD suppression diode
(b) Low capacitance unidirectional
Combined capacitance reducing ESD suppression diode
(c) bidirectionality
Two back-to-back ESD suppression bidirectional diodes
There should be no residual ends in signal lines.
Do not reduce the effective area of ground copper platinum in order to save costs.
In order to shorten the length of the signal line, use as many vias as possible for the ground line.
Install the protective TVS tube, install the device copper platinum position on the signal line as much as possible, and keep the TVS as close as possible to the input terminal.
Simple signal line protection design example:
Case: Single HDMI TMDS channel
As can be seen from the above figure, the 100Ohm differential high-speed transmission line can be regarded as basically unchanged with the addition of protection devices and without the protection device!
The maximum rise time of TDR measurement specified by the HDMI 1.3a standard is 200 ps. Relevant institutions have measured the TDR with the addition of ESDLC5V0D9U. The results are as follows：
* As can be seen from the above figure, after inputting 1 pulse, the rise time of the protection device is increased to 180ps (rising to 90% and falling to 10%). Since the TDR measurement of the impedance allowed by the HDMI specification is an upper limit of 200 ps The ratio is 25%, that is, 250ps, which meets the HDMI 1.3a standard requirements, so there is no need to compensate for the influence of ESDLC5V0D9U from the layout when designing the PCB.
When there are requirements for ultra-low capacitance or ultra-high frequency on the transmission line, such as: 3.0GBd and 4.0GBd of the HDMI 1.3a standard (referring to 1 HDMI TMDS connection for 3 channels), then we can perform very Perfect compensation.
Note: Z1 can calculate the wire impedance value based on the conductor conductivity.
Cd refers to the capacitance of the protection device.
L length is usually calculated as a compensation length of 2~3mm.
(The above design ideas are compiled by our Yinte R&D team after testing. We will conduct further research and exploration. For more details, pay attention to our company's official release)
