Smart Module Series
SC200L_Series(Dual-band Wi-Fi)_Hardware_Design 47 / 111
A reference circuit for SD card interface is shown as below.
SD_CMD
SD_DATA3
SD_DATA2
SD_CLK
SD_DATA0
SD_DET
SD_DATA1
P1-DAT2
P2-CD/DAT3
P3-CMD
P4-VDD
P5-CLK
P8-DAT1
GND
P6-VSS
P7-DAT0
DETECTIVE
GND
GND
GND
1
2
3
4
5
6
7
8
9
10
11
12
13
SD_VDD
33R
33R
33R
33R
33R
33R
1K
33 pF
4.7
μF
Module
R7
R8
R9
R10
R11
R12
R13
D1
D2
D3
D4
D5
D6
D7
D8
C1
C2
SD Card Connector
GND
Figure 19: Reference Circuit for SD Card Interface
SD_VDD supplies power for the SD card and can provide up to 400 mA output current. Due to the high
output current, it is recommended that the trace width should be 0.5 mm or above. To ensure the stability
of output power, add a 4.7
μF and a 33 pF capacitor in parallel near the SD card connector.
SD_CMD, SD_CLK, SD_DATA0, SD_DATA1, SD_DATA2 and SD_DATA3 are all high-speed signal
traces. In PCB design, control the characteristic impedance of these traces to
50 Ω ±10 %, and avoid
crossing them with other traces. It is recommended to route the traces on the inner layer of PCB and keep
them of the same length. Additionally, SD_CLK needs separate ground shielding.
Layout guidelines:
⚫
Control the characteristic impedance of these traces to
50 Ω ±10 % and add ground shielding.
⚫
The trace length difference between SD_CLK and other signal traces like SD_CMD and SD_DATA
should not exceed 1 mm.
Table 16: SD Card Signal Trace Length Inside the Module
Pin No.
Signal
Length (mm)
39
SD_CLK
46.42
40
SD_CMD
46.08
41
SD_DATA0
49.07
42
SD_DATA1
49.62