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A reference circuit for the SD card interface is shown below.
SD_DATA2
SD_DATA3
SD_CMD
SD_CLK
SD_DATA0
SD_DATA1
SD_DET
GND
Module
SD_LDO21 is the power supply for the SD card and can provide up to 841 mA output current. Due to the
high output current, it is recommended that the trace width should be at least 0.8 mm. To ensure output
current stability, 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 lines.
In PCB design, control the characteristic impedance of them to 50 Ω, and do not cross them with other
traces. It is recommended to route the traces on the inner layer of the PCB and keep them of the same
length. Additionally, SD_CLK needs ground shielding separately.
Trace length requirements:
⚫
Control the impedance to 50 Ω ± 10 % and add ground shielding.
⚫
Keep the trace length difference among SD_CLK, SD_CMD and SD_DATA less than 2 mm.
Table 15: SD Card Trace Length Inside the Module
Pin No.
39
40
41
42
43
SC206E_Series_Hardware_Design
LDO15A_1V8
R1
R2
R3
120K
NM_51K
NM_51K NM_10K NM_51K NM_51K
R7
33R
R8
33R
R9
33R
R10
33R
R11
33R
R12
33R
R13
1K
D1
D2
D3
Figure 17: Reference Circuit for the SD Card Interface
Signal
SD_CLK
SD_CMD
SD_DATA0
SD_DATA1
SD_DATA2
SD_LDO21
SD_LDO4
R4
R5
R6
R14
0R
C1
D4
D5
D6
D7
4.7 μF
Length (mm)
35.01
35.12
34.98
35.04
34.98
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
50 / 115
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