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SIM800L(MT6261)_Hardware Design_V1.01 51 2016-07-07
interface, audio interface, and so on.
5.2.1 Antenna Interface
The length of trace between pin output and connector should be as short as possible;
Do not trace RF signal over across the board;
The RF signal should be far away from SIM card, power ICs.
5.2.2. Power Supply
Not only VBAT but also return GND are very important in layout;
The positive line of VBAT should be as short and wide as possible;
The correct flow from source to VBAT pin should go though Zener diode then huge capacitor;
Pin 2, Pin 43, Pin 44 and Pin45 are GND signals, and shortest layout to GND of power source
should be designed;
There are 12 GND pads in middle of module; these pads could enhance the GND performances. On
the upper layer of these pads, do not trace any signal if possible.
5.2.3 SIM Card Interface
SIM card holder has no anti-EMI component inside. Thus SIM card interface maybe interfered,
please pay more attention on this interface during layout;
Ensure SIM card holder is far way from antenna or RF cable inside;
Put SIM card holder near the module, as nearer as possible;
Add ESD component to protect SIM_CLK, SIM_DATA, SIM_RST and SIM_VDD signals which
should be far away from power and high-speed-frequency signal.
5.2.4 Audio Interface
The signal trace of audio should far away from antenna and power;
The audio signal should avoid to parallel with VBAT trace.
5.2.5 Others
It is better to trace signal lines of UART bunched, as well as signals of USB.
5.3 Recommended PCB Layout
Based on above principles, recommended layout is shown in the following illustration.
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