Smart LTE Module Series
SC66 Hardware Design
SC66_Hardware_Design 63 / 139
A reference circuit for SD card interface is shown below.
SD_CMD
120K
NM_51K
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
33R
33R
33R
33R
33R
33R
1K
33pF
1uF
Module
R1
R2
R3
R4
R5
R6
NM_51K NM_10K NM_51K NM_51K
R7
R8
R9
R10
R11
R12
R13
D1
D2
D3
D4
D5
D6
D7
D8
C1
C2
SD Card Connector
LDO13A_1P8
SD_VDD
SD_PU_VDD
Figure 21: Reference Circuit for SD Card Interface
SD_VDD is a peripheral driver power supply for SD card. The maximum drive current is 600mA. Because
of the high drive current, it is recommended that the trace width is 0.5mm or above. In order to ensure the
stability of drive power, a 1uF and a 33pF capacitor should be added in parallel near the SD card
connector.
CMD, CLK, DATA0, DATA1, DATA2 and DATA3 are all high speed signal lines. In PCB design, please
control the characteristic impedance of them as 50
Ω, and do not cross them with other traces. It is
recommended to route the trace on the inner layer of PCB, and keep the same trace length for CLK, CMD,
SD_VDD
63
PO
Power supply for SD card
Vnorm=2.95V
I
O
max=600mA
SD_PU_
VDD
179
PO
SD card pull-up power
supply
Support 1.8V/2.95V power supply;
The maximum drive current is 50mA.
SD_CLK
70
DO
High speed digital clock
signal of SD card
Control characteristic impedance as
50
Ω.
SD_CMD
69
IO
Command signal of SD card
SD_DATA0
68
IO
High speed bidirectional
digital signal lines of SD
card
SD_DATA1
67
IO
SD_DATA2
66
IO
SD_DATA3
65
IO
SD_DET
64
DI
SD card insertion detection
Active low.
