Smart Module Series
SC20_Series_Hardware_Design 48 / 133
To avoid cross-talk between USIM_DATA and USIM_CLK, keep them away from each other and
shield them with ground. USIM_RST also needs ground protection.
In order to offer good ESD protection, it is recommended to add a TVS diode array with parasitic
capacitance not exceeding 50 pF. 22 Ω resistors should be added in series between the module and
(U)SIM card to suppress EMI spurious transmission and enhance ESD protection. Please note that
the (U)SIM peripheral circuit should be close to the (U)SIM card connector.
The 33 pF capacitors should be added in parallel on USIM_DATA, USIM_CLK and USIM_RST signal
lines to filter RF interference, and they should be placed as close to the (U)SIM card connector as
possible.
3.12. SD Card Interface
The SD card interface of SC20 series supports SD 3.0 protocol and 4-bit SDIO. The pin definition is
shown below.
Table 15: Pin Definition of SD Card Interface
Pin Name Pin No.
I/O Description Comment
SD_LDO11 38 PO SD card power supply
Vnom = 2.95 V
I
O
max = 600 mA
SD_LDO12 32 PO
1.8/2.95 V output power for SD card
pull-up circuits
Vnom = 1.8/2.95 V
I
O
max = 50 mA
SD_CLK 39 DO SD card clock
Control characteristic
impedance as 50 Ω.
SD_CMD 40 DIO
SD card command
SD_DATA0 41 DIO
SDIO data bit 0
SD_DATA1 42 DIO
SDIO data bit 1
SD_DATA2 43 DIO
SDIO data bit 2
SD_DATA3 44 DIO
SDIO data bit 3
SD_DET 45 DI SD card hot-plug detect Active low.
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