
CLM920_NC3_LTE Module hardware manual
Shanghai Yuge Information Technology co., LTD
- 38 -
The USIM interface cable is recommended to use ONSEMI's SMF15C device for ESD
protection. The peripheral circuit components should be placed close to the card holder.
The SIM card holder is close to the module layout.
The USIM card circuit is susceptible to radio frequency interference and does not
recognize or drop the card. Therefore, the card slot should be placed as far as possible
from the RF radiation of the antenna. The card trace should be as far away as possible
from the RF, power supply and high-speed signal lines.
The USIM_DATA pin needs to be pulled up to the USIM_VDD pin by a 15K resistor.
UIM_DET is the USIM card insertion or non-insertion detection pin. It is high by default.
The SIM card status can be detected by this PIN pin during hot plug application.
To avoid transient voltage overload, the USIM interface requires a 22R resistor in series
with each other on the signal line path.
The ground of the USIM deck and the ground of the module should maintain good
connectivity.
3.7.2 UIM_DET Hot Swap Reference Design
The CLM920 NC3 module supports the USIM card hot plug function.
The UIM_DET pin acts as an input detection pin to determine whether the USIM card is
inserted or not. The UIM_DET pin defaults to a pull-up high. The hot plug function can be
turned on or off by AT+HOSCFG. This function is off by default (see the AT command set for
details).
Table 3-12 SIM card hot swap detection pin definition
NO.
AT command
UIM_DET status
Functional description
1
AT+HOSCFG=1,1
Ligh
SIM card insertion, UIM_DET is high
2
AT+HOSCFG=1,0
Low
SIM card insertion, UIM_DET is low