User Guide

GM500-U1G_A

Hardware Development Guide

Figure 2–10Reference Circuit of the 8 Pin USIM Card

GM500-U1G_A supports USIM card hot-plugging via the USIM_ DETECT pin. For details, refer to document [AT Command

Reference Guide of Module Product GM500-U1G_A]. If you do not need the USIM card detect function, keep USIM_ DETECT

unconnected.

The reference circuit for using a 6-pin USIM card socket is illustrated as the following figure.

Figure 2–11Reference Circuit of the 6 Pin USIM Card

NOTE:

 R14~R16 and D6 are applied to suppress the EMI spurious transmission and enhance the ESD

protection.D6 should be closed to J4

 The value of C33 should be less than 1uF.

In order to enhance the reliability and availability of the USIM card in customer’s application, please follow the following criterion

in the USIM circuit design:

 Keep layout of USIM card as close as possible to the module. Assure the possibility of the length of the trace is less than

50mm.

 Keep USIM card signal away from RF and VBAT alignment.

 Assure the ground between module and USIM cassette short and wide. Keep the width of ground and USIM_VCC no less

than 0.5mm to maintain the same electric potential. The decouple capacitor of USIM_VCC should be less than 1uF and must

be near to USIM cassette.

 To avoid cross-talk between USIM_DATA and USIM_CLK, keep them away with each other and shield them with surrounded

ground.

 In order to offer good ESD protection, it is recommended to add TVS such as WILL (http://www.willsemi.com) ESDA6V8AV6.

The 33Ω resistors should be added in series between the module and the USIM card so as to suppress the EMI spurious

transmission and enhance the ESD protection. Please note that the USIM peripheral circuit should be close to the USIM card

socket.

 The pull-up resistor on USIM_DATA line can improve anti-jamming capability when long layout trace and sensitive occasion

is applied.

2.8.2. Design Considerations for USIM Card Holder

For 8-pin USIM card holder, it is recommended to use Molex 91228.

Please visithttp://www.molex.com for more information.