Quectel EG21-G Reference Design page 22

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D
C
B
Notes:
1. The pin 34 (VDD_SDIO) on the module can only be used for SDIO pull-up resistors and its maximum output current is 50mA.
2. The supply voltage range of VDD for SD card is 2.7V ～ 3.6V and sufficient current up to 0.8A needs to be provided.
3. To avoid the jitter of bus, resistors R1204 ～ R1208 are needed to pull up SDIO to VDD_SDIO.
The value of these resistors is between 10kΩ ～ 100kΩ and the recommended value is 100kΩ.
4. In order to adjust signal quality, it is recommended to add 0Ω resistors R1209 ～ R1214 in series between the module and the SD card connector.
The bypass capacitors C1206 ～ C1211 are reserved and not mounted by default.
5. It is recommended to add ESD protection devices near the pins of SD card connector. The parasitic capacitance of ESD protection devices should be smaller than 15pF.
6. Keep SDIO signals far away from other sensitive circuits/signals such as RF circuits, analog signals, etc, as well as noisy signals such as clock and DC-DC signals, etc.
7. Route SDIO signals with 50Ω±10% impedance. It is important to route SDIO signals with total grounding, and the total trace length should be less than 23mm.
A
8. It is recommended to keep the trace length difference between CLK and DATA/CMD less than 1mm.
9. Make sure the adjacent trace spacing is two times of the trace width and the bus capacitance is less than 15pF.
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5
SD Card Interface Design
R1201
[5,11] VDD3V3
[4] SD_PWR_EN
[3] VDD_SDIO
R1204
100K
R1209 0R
[3]
SD2_CLK
R1210 0R
[3] SD2_CMD
R1211 0R
[3] SD2_DATA3
R1212
0R
[3] SD2_DATA2
R1213
0R
[3] SD2_DATA1
R1214
0R
[3] SD2_DATA0
C1206
NM
5
4
4 3
Q1201
0R
S D
SI2333
C1201
R1202
10K 100nF
R1203
100K
Q1202
DTC043ZE
R1208
R1205 R1206 R1207
100K 100K 100K 100K
D1201 D1202 D1203
C1207 C1208 C1209 C1210 C1211
NM NM NM NM
NM
ESD9L5.0ST5G
3
2
C1202
C1203 C1205
C1204
33pF
100nF 10pF
100uF
J1201
VDD
CLK
CMD
DATA3
DATA2
DATA1
DATA0
VSS
D1204 D1205 D1206
DETECT
SD card connector
VDD_EXT
R1215
120K
R1216
1K
D1207
ESD9X3.3ST5G
Quectel Wireless Solutions
DRAWN BY
Lorry XU
CHECKED BY
Woody WU
SHEET
2
1
D
C
B
[3]
SD2_INS_DET
A
PROJECT TITLE
EG21-G Reference Design
VER
SIZE
A2 1.0
13 OF 14 DATE 2019/12/5
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