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A reference circuit for SD card interface is shown as below.
SD_DATA2
SD_DATA3
SD_CMD
SD_CLK
SD_DATA0
SD_DATA1
SD_DET
GND
Module
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.
39
40
41
42
SC200L_Series(Dual-band Wi-Fi)_Hardware_Design
R7
33R
R8
33R
R9
33R
R10
33R
R11
33R
R12
33R
R13
1K
D1
D2
D3
Figure 19: Reference Circuit for SD Card Interface
Signal
SD_CLK
SD_CMD
SD_DATA0
SD_DATA1
SD_VDD
C1
D4
D5
D7
D6
4.7 μF
Length (mm)
46.42
46.08
49.07
49.62
Smart Module Series
1
P1-DAT2
2
P2-CD/DAT3
3
P3-CMD
4
P4-VDD
5
P5-CLK
6
P6-VSS
7
P7-DAT0
8
P8-DAT1
9
DETECTIVE
10
GND
D8
C2
11
GND
12
33 pF
GND
13
GND
SD Card Connector
47 / 111
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