LTE-A Module Series
EM121R-GL Hardware Design
EM121R-GL Hardware Design 37 / 80
Module
(U)SIM Card
Connector
USIM_DET
USIM_DATA
USIM_CLK
RST
CLK
CD
IO
USIM_VDD
USIM_VDD
USIM_RST
VCC
GND
VPP
GND
ESD
Note:
All these resistors, capacitors and TVS should be close to (U)SIM card connector in PCB layout.
10-20k
22R
22R
22R
3
3
p
F
3
3
p
F
3
3
p
F
100 nF
Figure 14: Reference Circuit for Normally Closed (U)SIM Card Connector
4.1.4. Normally Open (U)SIM Card Connector
With a normally open (U)SIM card connector, CD1 and CD2 of the connector are disconnected when
there is no (U)SIM card inserted. (U)SIM card detection by low level is applicable to this type of connector.
After executing AT+QSIMDET=1,0 to enable the (U)SIM hot-plug: when a (U)SIM card is inserted,
USIM_DET will change from high to low level; when the (U)SIM card is removed, USIM_DET will change
from low to high level.
⚫
When the (U)SIM is absent, CD1 is open from CD2 and USIM_DET is at high voltage level.
⚫
When the (U)SIM is inserted, CD1 is connected to GND and USIM_DET is at low voltage level.
The following figure shows a reference design of (U)SIM interface with a normally open (U)SIM card
connector.
Module
(U)SIM Card
Connector
USIM_DET
USIM_DATA
USIM_CLK
RST
CLK
CD1
IO
USIM_VDD
USIM_VDD
USIM_RST
VCC
GND
VPP
GND
TVS
10-20k
22R
22R
22R
3
3
p
F
3
3
p
F
3
3
p
F
100 nF
0R
CD2
NOTE:
All these resistors, capacitors and TVS should be close to (U)SIM card connector in PCB layout.
Figure 15: Reference Circuit for Normally Open (U)SIM Card Connector