Product Info

LTE Standard Module Series
EC21_Series_Mini_PCIe_Hardware_Design
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Keep placement of (U)SIM card connector to the module as close as possible. Keep the trace length
as less than 200 mm as possible.

Keep (U)SIM card signals away from RF and power supply traces.

To avoid cross-talk between USIM_DATA and USIM_CLK, keep them away from each other and
shield them with surrounded ground.

For better ESD protection, it is recommended to add a TVS diode with parasitic capacitance not
exceeding 15 pF.

The 0 Ω resistors should be added in series between the module and the (U)SIM card connector to
facilitate debugging. The 33 pF capacitors are used for filtering interference of EGSM900. Please
note that the (U)SIM peripheral circuit should be close to the (U)SIM card connector.

The pull-up resistor on USIM_DATA trace can improve anti-jamming capability when long layout
trace and sensitive occasion are applied, and should be placed close to the (U)SIM card connector.
3.7. USB Interface
EC21 series Mini PCIe provides one integrated Universal Serial Bus (USB) interface which complies with
USB 2.0 specification. It can only be used as a slave device. EC21 series Mini PCIe supports high-speed
(480 Mbps) mode and full-speed (12 Mbps) mode.
The USB interface is used for AT command communication, data transmission, GNSS NMEA output,
software debugging, firmware upgrade and voice over USB.
The following table shows the pin definition of USB interface.
Table 9: Pin Definition of USB Interface
Pin Name Pin No. I/O Description Comment
USB_DM 36 AIO USB differential data (-) Require differential impedance of 90 Ω.
USB_DP 38 AIO USB differential data (+) Require differential impedance of 90 Ω.