microSD vs. SD Bus Interfaces
Comparing 2 standards across 13 specifications. 13 key differences identified.
microSD (originally developed as TransFlash / T-Flash by SanDisk in 2004 and ratified by the SD Association in 2005) is the ultra-compact form factor of the Secure Digital family. Measuring 15.0 × 11.0 × 1.0 mm (approximately 20% the size of a standard SD card), it is the universal removable storage medium for smartphones, action cameras, drones, and handheld gaming consoles.
SD Bus Interfaces define the physical and electrical signaling architectures through which SD and microSD cards transfer data with host controllers. Spanning legacy Default/High Speed, Ultra High Speed tiers (UHS-I up to 104 MB/s, UHS-II up to 312 MB/s, UHS-III up to 624 MB/s), and PCIe/NVMe-based SD Express (up to 3,940 MB/s).
Specification Comparison Table
13 Parameters| Parameter / Spec | ||
|---|---|---|
|
Governing Body
|
SD Association (SDA) | — |
|
Original Name
|
TransFlash (TF Card / T-Flash by SanDisk, 2004) | — |
|
Physical Dimensions
|
15.0 mm × 11.0 mm × 1.0 mm (Weight: ~0.25 g) | — |
|
Pin Configurations
|
8 pins (UHS-I / Legacy) / 16 pins (UHS-II dual-row) | — |
|
Capacity Standards
|
microSD (≤2GB), microSDHC (4–32GB), microSDXC (64GB–2TB), microSDUC (up to 128TB) | — |
|
Operating Voltages
|
2.7V–3.6V (Standard) / 1.8V (UHS-I signal) | — |
|
Passive Adapter Compatibility
|
Electrically identical to full-size SD (100% pin-compatible via passive sleeve adapter) | — |
|
Default Speed (DS) / High Speed (HS)
|
— | 12.5 MB/s (25 MHz @ 3.3V) / 25 MB/s (50 MHz @ 3.3V) |
|
UHS-I (SD 3.01)
|
— | SDR12 (12.5 MB/s), SDR25 (25 MB/s), SDR50 (50 MB/s), DDR50 (50 MB/s), SDR104 (104 MB/s @ 208 MHz 1.8V) |
|
UHS-II (SD 4.0)
|
— | 156 MB/s (Full Duplex) / 312 MB/s (Half Duplex) via 2nd pin row LVDS (0.26V) |
|
UHS-III (SD 6.0)
|
— | 312 MB/s (Full Duplex) / 624 MB/s (Full Duplex dual-lane LVDS) |
|
SD Express (SD 7.0 / 8.0)
|
— | 985 MB/s (PCIe 3.0 x1), 1970 MB/s (PCIe 4.0 x1 / 3.0 x2), up to 3940 MB/s (PCIe 4.0 x2) |
|
SD Express Protocol Stack
|
— | PCI Express (PCIe) + NVM Express (NVMe v1.3/1.4) over SD pins |