Quectel UC200T-EM Hardware Design page 36

VDD_SDIO* 34
SD_INS_DET* 23
The following figure shows a reference design of SD card interface.
Module
VDD_SDIO
R7
NM
R1 0R
SDC2_DATA3
R2 0R
SDC2_DATA2
R3 0R
SDC2_DATA1
R4 0R
SDC2_DATA0
R5 0R
SDC2_CLK
R6 0R
SDC2_CMD
SD_INS_DET
NM
In SD card interface design, in order to ensure good communication performance with SD card, the
following design principles should be complied with:
⚫ The voltage range of SD card power supply VDD_3V is 2.7V~3.6V and a sufficient current up to 0.8A
should be provided. As the maximum output current of VDD_SDIO is 50mA which can only be used
for SDIO pull-up resistors, an externally power supply is needed for SD card.
To avoid jitter of bus, resistors R7~R11 are needed to pull up the SDIO to VDD_SDIO. Value of these
⚫
resistors is among 10KΩ~100KΩ and the recommended value is 100KΩ. VDD_SDIO should be used
as the pull-up power.
⚫ In order to adjust signal quality, it is recommended to add 0Ω resistors R1~R6 in series between the
module and the SD card. The bypass capacitors C1~C6 are reserved and not mounted by default. All
resistors and bypass capacitors should be placed close to the module.
In order to offer good ESD protection, it is recommended to add a TVS diode on SD card pins near
⚫
the SD card connector with junction capacitance less than 15pF.
Keep SDIO signals far away from other sensitive circuits/signals such as RF circuits, analog signals,
⚫
as well as noisy signals such as clock signals, DCDC signals.
⚫ It is important to route the SDIO signal traces with total grounding. The impedance of SDIO data
trace is 50Ω (±10%).
⚫ Make sure the adjacent trace spacing is two times of the trace width and the load capacitance of
UC200T-EM_Hardware_Design
PO SD card SDIO bus pull up power
DI SD card insertion detect
R8 R9 R10
NM NM NM
C1 D1 C2 D2 C3 D3 C4
NM NM NM
Figure 15: Reference Circuit of SD Card Interface
UMTS/HSPA(+) Module Series
UC200T-EM Hardware Design
+
C10 C9
R11
100uF 100nF
NM
D4 C5 D5 C6 D6
D7
NM NM
If unused, keep it open.
1.8V/2.8V power domain.
If unused, keep it open.
1.8V/2.8V power domain.
If unused, keep it open.
SD Card Connector
VDD_3V
VDD
C8 C7
33pF 10pF
CD/DAT3
DAT2
DAT1
DAT0
CLK
CMD
DETECTIVE
VSS
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