Product Info

LTE Module Series

EG21-G Hardware Design

EG21-G_Hardware_Design 40 / 100

In order to enhance the reliability and availability of the (U)SIM card in customers’ applications, please

follow the criteria below in (U)SIM circuit design:

 Keep placement of (U)SIM card connector to the module as close as possible. Keep the trace length

as less than 200mm as possible.

 Keep (U)SIM card signals away from RF and VBAT traces.

 Assure the ground between the module and the (U)SIM card connector short and wide. Keep the

trace width of ground and USIM_VDD no less than 0.5mm to maintain the same electric potential.

Make sure the bypass capacitor between USIM_VDD and USIM_GND less than 1uF, and place it as

close to (U)SIM card connector as possible. If the ground is complete on customers’ PCB,

USIM_GND can be connected to PCB ground directly.

 To avoid cross-talk between USIM_DATA and USIM_CLK, keep them away from each other and

shield them with surrounded ground.

 In order to offer good ESD protection, it is recommended to add a TVS diode array whose parasitic

capacitance should not be more than 15pF. The 0Ω resistors should be added in series between the

module and the (U)SIM card to facilitate debugging. The 33pF capacitors are used for filtering

interference of EGSM900MHz. Please note that the (U)SIM peripheral circuit should be close to the

(U)SIM card connector.

 The pull-up resistor on USIM_DATA line 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.

3.10. USB Interface

EG21-G contains one integrated Universal Serial Bus (USB) interface which complies with the USB 2.0

specification and supports high-speed (480Mbps) and full-speed (12Mbps) modes. The USB interface is

used for AT command communication, data transmission, GNSS NMEA sentences output, software

debugging, firmware upgrade and voice over USB*. The following table shows the pin definition of USB

interface.

Table 10: Pin Description of USB Interface

Pin Name

Pin No.

I/O

Description

Comment

USB_DP

USB differential data bus (+)

Require differential

impedance of 90Ω

USB_DM

USB differential data bus (-)

Require differential

impedance of 90Ω

USB_VBUS

USB connection detection

Typical 5.0V

GND

Ground