Verdin Carrier Board Design Guide
Preliminary
– Subject to Change
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Depending on the Verdin module, the IO voltage of the card-detect (SD_1_CD#) and the power-
enable (SD_1_PWR_EN) signals may also change together with the SD bus signals from 3.3V to
1.8V. The circuit on the carrier board need to be able to work with both IO voltage levels. The card
detect signal is an open-drain input with the pull-up resistor on the module. This means the carrier
board has only to short this pin simply to ground when the card is inserted.
The SD card interface does not have a dedicated reset input. The only way to reset a card is to
power cycle it. When changing the bus voltage from 1.8V to 3.3V, officially the card needs to be
reset. A reset could also be required if the card is not responding anymore. However, most cards
work without the need of a reset. Nevertheless, we recommend implementing a card-reset by
adding a switch to the supply voltage for the SD card. The Microchip MIC94073 power switch in
the reference schematic features a built-in logic shifter which can handle 1.8V or 3.3V as logic
high for the SD_1_PWR_EN signal.
There is no dedicated write-protection signal available on the standard Verdin pin-out. Any free
GPIO capable signal can be used if the write-protection function is required. The ESD protection
diodes are optional. Whether the protection is required or not depends on how accessible the card
slot is to the user.
Figure 37: 4bit SD Card Reference Schematic
2.8.3
Unused SD/MMC/SDIO Interface Signal Termination
All unused SD interface signals can be left unconnected. If the SD/MMC/SDIO ports is unused, the
signal could be used as GPIO. Check the datasheet of the Verdin module whether there are any
restrictions for using the signals as GPIOs.
2.9
I
2
C
The Verdin module standard features four I
2
C interfaces. The interface I2C_1 is a general purpose
I
2
C and is in the "Always Compatible" interface group. The additional three I
2
C port are in the
"Reserved" group and are dedicated to other interfaces. I2C_2_DSI is dedicated for the MIPI DSI
port, I2C_3_HDMI is dedicated to the HDMI port, and I2C_4_CSI is dedicated for the MIPI CSI port.
Check the Verdin datasheet whether these I
2
C ports can be used as general-purpose interfaces.
Some modules do not provide all four I
2
C ports. Whether a port is available or not, depends also
whether the interface they are dedicated to is existing.
The I
2
C interfaces do not feature any pull-up resistors on the module. It is required to add pull-up
resistors for the data and clock lines on the carrier board. The pull-up resistor value is typically
100nF
16V
C102
10uF
10V
C104
GND
+V3.3_SD
1nF
50V
C101
100pF
50V
C103
GND
MIC94073YMT
VOUT
1
GND
2
VIN
3
ENABLE
4
GND-TH
5
IC20
GND
+V3.3_SW
SD_1_D2
100nF
16V
C100
GND
SD CARD POWER SWITCH
DAT_3
1
CMD
2
VCC
4
CLK
5
GND
6
DAT_0
7
DAT_1
8
CD
10
DAT_2
9
GND
3
WP
11
693063020911
X55A
S
H
IE
L
D
S1
S2
S3
S4
693063020911
X55B
GND
+V3.3_SD
SD_1_D3
SD_1_CMD
SD_1_CLK
SD_1_D0
SD_1_D1
SD_1_D0
SD_1_D2
SD_1_D3
SD_1_D1
SD_1_CMD
SD_1_CLK
GND
TP8
R114
100K
SD_1_D2
70
SD_1_D3
72
SD_1_CMD
74
SD_1_PWR_EN
76
SD_1_CLK
78
SD_1_D0
80
SD_1_D1
82
SD_1_CD#
84
X1R
2309409 -2
GND
SD_1_CD#
SD_1_PWR_EN
ESD9101P2T5G
D36
ESD9101P2T5G
D35
ESD9101P2T5G
D34
ESD9101P2T5G
D33
ESD9101P2T5G
D13
ESD9101P2T5G
D22
ESD9101P2T5G
D31
ESD9101P2T5G
D32
GND
GND
GND
GND
GND
GND
GND
SD_1_CD#
SD_1_PWR_EN