Fibocom L850-GL - 3.5.2 USIM Interface Circuit

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L850-GL Hardware User Manual Page 36 of 54
Figure 3-16Reference Circuit for N.C. SIM Card Slot
The principles of the N.C.SIM card slot are described as follows:
 When the SIM card is detached, it connects the short circuit between CD and SW pins, and drives the
SIM_DETECT pin low.
 When the SIM card is inserted, it connects an open circuit between CD and SW pins, and drives the
SIM_DETECT pin high.
3.5.2.2 N.O. SIM Card Slot
The reference circuit design for N.O. (Normally Open) SIM card slot is shown in Figure 3-17:
Figure 3-17 Reference Circuit for N.O. SIM Card Slot
The principles of the N.O.SIM card slot are described as follows:
 When the SIM card is detached, it connects an open circuit between CD and SW pins, and
drives the SIM_DETECT pin low.
 When the SIM card is inserted, it connects the short circuit between CD and SW pins, and drives
the SIM_DETECT pin high.