MeiG Smart product technical information
SLM758
Hardware Design Guide
Page 65
5.2.4. MIPI
MIPI is a high-speed signal line. Users must pay attention to protection during the
layout stage, so that they are away from the signal lines that are easily interfered. The GND
processing must be performed on the upper and lower sides, and the traces are differential
pairs. 100 ohm differential impedance matching is performed. Ensure impedance
consistency and do not bridge different GND planes as much as possible.
The MIPI interface selects a small-capacity TVS when selecting an ESD device. It is
recommended that the parasitic capacitance be less than 1pF.
The MIPI routing requirements are as follows:
The total length of the cable does not exceed 300mm
It is required to control 100 ohm differential impedance with an error of ±10%.
The error of the differential line length within the group is controlled within 0.7mm.
The length error between groups is controlled within 1.4mm.
5.2.5. USB
The module supports high-speed USB interface at a rate of 480Mbps. The user recommends
adding a common-mode inductor during the schematic design phase to effectively suppress
EMI interference. If you need to increase the static protection, please select a TVS tube with a
parasitic capacitance of less than 1pF. Please refer to the following notes when planning
Layout:
The common mode inductor should be close to the side of the USB connector.
Requires control of 90 ohm differential impedance with an error of ±10%.
The differential line length error is controlled within 6mm.
If the USB has a charging function, please note that the VBUS cable is as wide as possible.
If there is a test point, try to avoid the split line and put the test point on the path of the trace.
Table 5.1: Internal USB cable length of the module
Pin
S
ignal
L
ength mm)
Length
E
rror
（
P-N
）
14
USB_DP
46.3
0.2mm
13
USB_DM
46.4
5.2.6.Audio
The module supports 3 analog audio signals. Analog signals are susceptible to interference
from high speed digital signals. So stay away from high-speed digital signal lines. The module
supports the GSM system, and the GSM signal can interfere with the audio by coupling and
conduction. Users can add 33pF and 10pF capacitors to the audio path to filter out coupling
interference. The 33pF capacitor mainly filters out the interference of the GSM850/EGSM900
band, and the 10pF capacitor mainly filters out the interference of the DCS1800 band. The
coupling interference of TDD has a great relationship with the PCB design of the user. In some
cases, the TDD of the GSM850/EGSM900 frequency band is more serious, and in some cases,
