User's Manual
Table Of Contents
- 1. Introduction
- 2. General Description
- 3. Simplified Block Diagram
- 4. Key Features
- 5. Product Specifications
- 6. Application Interface
- 7. Mounting the Module onto the Application Board
- 8. Package
- 9. Terms and Abbreviations
Neo_M680 Hardware User Guide V1.0
Copyright Neoway Techlology Co., Ltd. Page 24 of 31
Figure 16a Reference design of SIM interface
Pin1=VCC, Pin2=RST, Pin3=CLK, Pin4=GND, Pin5=VPP, Pin6=DATA
Figure 16b a sample of SIM card socket
Figure 16c the recommended ESD diode array
M680 SIM interface is 3V/1.8V compatible. VSIM is for SIM power and can supply a 30mA
current.
SIM_DATA is internally pulled up with a 5KΩ resistor. External pull-up resistor is not needed.
SIM_CLK can work at several frequencies, but at 3.25MHz typically.
ESD protectors, such as ESD diodes or ESD Varistors, are recommended on the SIM signals,
especially in automotive electronics or other applications with badly ESD. The total equivalent
capacitance on any SIM signal, include the junction capacitance of the ESD diode and the distributed
capacitance of PCB trace, can’t be higher than 120pF.
If the SIM card is installed in a closed case without human touch or ESD, 22~33pF MLCC
capacitors can replace the ESD diodes for cost down.
SIM card is sensitive to GSM TDD noise and RF interference. So, the rule is very important in the
PCB design, listed as the following.