SD card PCB/SD card PCB layout requirements
AKEN Cheung 封装基板制造商
Director . Advanced packaging IC substrate manufacturer. Advantages: Cost reduction with realiability. FCBGA/ FCCSP/ CSP/ SiP/ Module/ BGA memory DDR3/DDR4/DDR5/ mmwave/ Embedded/ PCB substrate, uHDI PCB etc. mSAP
1. Definition
Micro SD card is a very small flash memory card whose format originated from the creation of SanDisk. Originally, this memory card was called T-Flash, and later renamed Trans Flash. The reason for renamed Micro SD was SD Association (SDA) Adopted Li. Other memory cards adopted by SDA include Mini SD and SD cards. It is mainly used in mobile phones, but because of its small size and increasing storage capacity, it has been used in GPS devices, portable music players and some flash memory disks. Its size is 15mm x 11mm x 1mm, which is almost the size of a fingernail, and it is the smallest memory card available. It can also be connected to the SD card slot through an SD adapter card. At present, MicroSD cards provide 128MB, 256MB, 512MB, 1G, 2G, 4G, 8G, 16G, 32G, 64G, 128G capacities (during the MWC 2014 World Mobile Communications Conference, SanDisk broke the tradition of memory cards with a maximum capacity of 64GB and officially released A Micro SD XC memory card with a capacity of up to 128GB.
2. Pin definition
Figure 1 SD card pin definition
SD card is also an interface device that is often plugged and unplugged, and the addition of electrostatic devices needs to be considered when designing the principle.
3. SD card layout and wiring requirements
1) The capacitor of VCC_SD needs to be placed close to the card socket pin for filtering, following the principle of large first and then small.
2) The TF card should be placed on the edge of the board as much as possible for easy insertion and removal. The ESD device should be placed close to the TF card. The wiring needs to pass through the ESD device before entering the SD card. Do not punch holes, as shown in Figure 2.
3) The SD card wiring is single-ended, with a control impedance of 50 ohms;
4) All the signal lines should be on the same layer as much as possible, which is conducive to the consistency of the signal. The wiring is separated from the high-frequency signal. If space permits, the ground should be covered by a single root. When the space is tight, the whole group should be covered by the ground. Processing, wiring needs to have a complete reference plane;
5) The clock signal of the SD card should be kept at a distance of about 20 mils from other signal lines. If there is space, it will be handled by the package.
6) The data lines in the group should not be too different, they need to be controlled within 400mil, and the total length of the trace should not be too long, try to control it within 12.5 inches to improve stability and compatibility.
④ All the signal lines of the SD card need to be processed with equal length, with the clock line as the target line, and the error can be controlled within 300 mils.
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