Altec GSM SOCKET AL7020S - Manual (Page 20)

AL7020S, AL7024S Designer’s Guide
Doc. No. DG_7024E Altec Electronic AG Seite 20 / 32
3.7.3 SIM Card Reader Integration:
SIM interface controls a 3V SIM only.
We add Transient Voltage Suppressor (TVS) diodes with low capacitance (less than
10pF) on signal connected to the SIM socket in order to prevent any Electrostatic
Discharge. They shall be placed as close as possible to the SIM socket. Following
references are used:
DALC208SC6 from ST Microelectronics, which will be connected, to SIMCLK and
SIMDATA.
ESDA6V1 from ST Microelectronics for the ESD protection of SIMVCC.
On the board near SIM connector, we also add on SIMVCC a 100nF capacitor in
parallel as close as possible to the SIM connector to minimize noise.
Schematic of SIM Interface:
3.7.4 Layout Restrictions:
For the SIM interface, length of the tracks between the GSM modem and the SIM
connector should be as short as possible (8cm).
EMI layout is recommended for SIMCLK signal.
SIMCLK
SIMVCC
D1
ESDA6V1L
1 2
3
P1
SIM-CARD-READER
1
2
3
5
6
7
4
8
VCC
RST
CLK
GND
VPP
I/O
PRES_IN
PRES_OUT
D2
DALC208SC6
1 2
4 5 6
3
SIMDATA
P1A
SOCKET MODEM
32
31
30
29
28
27
26
25
24
C1
100NF
RESET
SIMRST
SIMCLK
SIMRST
SIMDATA
SIMVCC
GND
Socket
Modem
SIM
connector
GND
GND
Less than 8 cm