MICRO SD CARD ADAPTER

The micro SD module is also known as the Micro SD card adapter. It is a simple solution for transferring data to and from a standard SD card for dual I/O voltage. This module has an SPI interface that can be directly compatible with Arduino UNO/MEG and another microcontroller. Thus it uses 5V or 3.3v supply. The micro SD card adapter module includes two main components i.e., voltage regulator and 74LVC125A chip for logic level shifting. 74LVC125A  is a 3.3V CMOS quadruple bus buffer gate with 5v tolerant I/O.

The Micro SD card operates at a standard voltage of 3.3V. We cannot directly connect the circuit that uses 5V logic. Any voltage that exceeds 3.6v is passed through the ultra-low dropout register and hence convert voltage 3.3V-6V to 3.3V. 74LVC125A chip performs interface logic from 3.3V-5V to 3.3V. This level shifting helps to interact with both 3.5V and 5V microcontrollers like Arduino. These are used in various applications such as data logger, audio-video graphics, etc.

Micro SD consists of six pins (GND, VCC, MISO, MOSI, SCK, CS), GND to ground, VCC is the power supply, MISO, MOSI, SCK is the SPI bus, CS is the chip select signal pin; 3.3V regulator circuit: LDO regulator output 3.3V as level converter chip, Micro SD card supply.

Micro SD can be interfaced in 2 ways. SPI mode and SDIO mode. SDIO mode is faster and used in mobile phones, digital cameras, etc. SDIO Mode is more complex than SPI Mode, hence SPI mode is used in most microcontrollers.