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L816-AM Hardware User Manual
Page 28 of 42
3.5.2 USIM Interface Circuit
3.5.2.1 N.C. SIM Card Slot
The reference circuit design for N.C. (Normally Closed) SIM card slot is shown in Figure 3-11:
Figure 3-11
Reference Circuit for N.C. SIM Card Slot
The principles for N.C. SIM card slot design are described as follows:
When the SIM card is detached, it connects the short circuit between CD and SW pins, and drives the
SIM1_CD pin low.
When the SIM card is inserted, it connects an open circuit between CD and SW pins, and drives the
SIM1_CD pin high.
Suggested SIM1_CD pin increase TVS to protect the pin.
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 3-12:
Figure 3-12 Reference Circuit for N.O. SIM Card Slot
