3 Application Interfaces
41
⚫ The filter capacitor and ESD device of SIM signal cable are placed close to the SIM card
slot. Less than 11pF capacitor is recommended for ESD device.
Routing points:
⚫ To reduce EMC problem, keep SIM signal line away from RF cable, power line, clock line
and high-speed data line.
⚫ Do not route the adjacent cables with the SIM signal line; otherwise, the cabling poses an
EMI risk. Design the other cables and SIM signal line to be perpendicular with each other
to reduce risk.
⚫ Ensure the ground connectivity and integrity of PCB environment and the connectivity and
integrity of SIM_GND. The nearest path connects to a clean system ground. To avoid
mutual interference, please separately ground SIM_CLK and SIM_DATA. If conditions do
not permit, at least the SIM signal must be grounded as a set.
⚫ The SIM signal line should be routed along the inner layer.
⚫ SIM card connector is covered by metal shield shell to improve EMS.
⚫ To ensure the integrity of signal, the cabling length from the module to SIM card should not
exceed 100mm. Longer cable will reduce signal quality.
⚫ It is recommended to make a clearance design for the PCB directly under the shrapnel of
the SIM card connector to avoid the green oil on the surface of the PCB being worn down
when the shrapnel is pressed down, resulting in a short circuit between the SIM card signal
line and the ground.
Hot Plug
The MG661 module supports (U)SIM card hot-plug function. The module determines whether
(U)SIM card is in place by detecting the status of USIM_PRESENCE pin. (U)SIM card hot-
plug function is disabled by default and needs to be enabled before use. When the
USIM_PRESENCE is at a high level, the module initializes the (U)SIM card after detecting
that the (U)SIM card is inserted, and registers the network after reading the (U)SIM card
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