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SMARC T335x Carrier Board Hardware Design Guide, Document Revision 1.2
2.5.2. SD/SDIO Implementation Guidelines
2.5.2.1. ESD Protection
To protect the SD interface of the module from over-voltage caused by
electrostatic discharge (
ESD
) and electrical fast transients (EFT), it is
highly recommended to use low capacitance steering diodes and transient
voltage suppression diodes that must be implemented on the carrier
board (for example
PACDN006MR
ESD
Suppressor from On
Semiconductor or
SR05 RailClamp
®' surge rated diode arrays from
Semtech,
http://semtech.com
).
2.5.2.2. SDIO_PWR_EN Signal
SDIO_PWR_EN
is a GPIO to control the switch of SD card power. When
this signal is pulled high, it will enable the SD card power. When this signal
is pulled down, it will turn off the SD card power.
If the system requires having the SD card boot functionality, this signal
has to be pull high at default state and the pull up resistor should be 4.7k
or less.
Figure 23: SDIO_PWREN Signal Reference Schematic