Quectel RM520N-GL - Normally Open (U)SIM Card Connector; U)SIM Card Connector Without Hot-Plug

5G Module Series

RM520N-GL_Hardware_Design 42 / 84

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.

Once (U)SIM hot-plug is enabled by executing AT+QSIMDET=1,0, a (U)SIM card insertion will drive

USIM_DET from high to low level, and the removal of it will drive USIM_DET from low to high level.

⚫ When the (U)SIM is absent, CD1 is open from CD2 and USIM_DET is at high level.

⚫ When the (U)SIM is present, CD1 is pull down to ground and USIM_DET is at low level.

The following figure shows a reference design for (U)SIM interface with a normally open (NO) (U)SIM

card connector.

Module (U)SIM Card

Connector

USIM_DET

USIM_DATA

USIM_CLK

RST

CLK

CD1

IO

USIM_VDD

USIM_RST

VCC

GND

VPP

GND

TVS array

10-20k

22 Ω

10 pF 10pF 10pF

100 nF

4.7k

CD2

NOTE: All these resistors, capacitors and TVS should be close to (U)SIM card connector in PCB layout.

Figure 16: Reference Circuit for Normally Open (U)SIM Card Connector

4.1.5. (U)SIM Card Connector Without Hot-Plug

If (U)SIM card hot-plug is not needed, please keep USIM_DET unconnected. A reference circuit for

(U)SIM card interface with a 6-pin (U)SIM card connector is illustrated by the following figure.