USB2251-NU-06 - USB 2.0 Flash Media Controller | Microchip
MPN: USB2251-NU-06 ✓ ActiveUSB2251-NU-06 Overview
A USB flash media card controller is a specialized interface IC that translates host-side USB traffic into commands understood by flash-memory media. Within the broader hierarchy, it is a USB interface controller, an interface IC, an integrated circuit, and a semiconductor designed for removable or embedded flash-storage applications. The USB2251 family supports Hi-Speed USB 2.0 operation and broad media-card interoperability for devices requiring direct access to flash storage.
The key features include USB 2.0 compatibility, a 24 MHz maximum operating clock, a 35 Mbps maximum data-transfer rate, I2C bus compatibility, and a 128-terminal surface-mount package. The 14 x 14 mm VTQFP format provides 128 electrical connections, allowing the controller to expose multiple media interfaces, control signals, data buses, and power-management connections. A tray package is listed by the distributor data for this ordering code.
Technically, the USB2251 belongs to Microchip's USB225x controller family, which is designed around a high-speed USB 2.0 host interface and flash-media-card control functions. Its 35 Mbps maximum transfer rate is materially faster than the 12 Mbps ceiling associated with Full-Speed USB operation, making it suitable for flash-media devices where transfer latency affects data synchronization, file copying, and application startup. The controller operates from a 3.3 V supply according to the distributor product listing.
Typical uses include USB flash-memory readers, portable storage devices, embedded storage systems, digital media equipment, and host systems that need a dedicated USB-to-flash bridge. In a card-reader implementation, the controller handles USB enumeration and transaction exchange with the host while transferring data to compatible flash media through the device's card-interface signals. The I2C-compatible interface can support configuration or management functions where the host or system controller requires them.
Designers should verify the complete 128-pin signal map, configuration options, voltage levels, clock requirements, and media-support matrix in the manufacturer datasheet before PCB release. Because no verified 128-terminal pin table was supplied, this page does not infer pin names or numbering. USB routing also requires careful controlled-impedance layout, short high-speed traces, solid reference planes, and compliant power distribution to avoid signal-integrity and EMC issues.
This page consolidates the verified manufacturer description, distributor package data, operating highlights, ordering information, and traceable web sources. It also distinguishes verified drop-in-family candidates from functional equivalents that would require a different footprint, helping engineers compare sourcing options without mistaking a merely similar USB storage controller for a pin-compatible replacement.
Drop-in alternatives for USB2251-NU-06 — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with USB2251-NU-06 (same form factor and footprint) — differing in Package Type.
USB2251I-NU-06
✅ Drop-In📋 Reference alternative (not in catalog)
USB2251-NU-05
✅ Drop-In📋 Reference alternative (not in catalog)
USB2250I-NU-06
✅ Drop-In📋 Reference alternative (not in catalog)
USB2250-NU-06
✅ Drop-InContact for price
View Datasheet →USB2250-NU-05
✅ Drop-InContact for price
View Datasheet →USB2251-NU-06 Specifications
| Product Type | USB 2.0 flash media card controller |
| Maximum Clock Frequency | 24 MHz |
| Maximum Data Transfer Rate | 35 Mbps |
| USB Compatibility | USB 2.0 |
| Bus Compatibility | I2C and USB |
| Supply Voltage | 3.3 V |
| Package Type | 128-terminal VTQFP |
| Package Dimensions | 14 x 14 mm |
| Terminal Pitch | 0.40 mm |
| Terminal Count | 128 terminals |
| Mounting Type | Surface mount |
| Packaging | Tray |
| Technology | CMOS |
| Device Classification | Specialized controller interface |
USB2251-NU-06 14 x 14 mm Pin Configuration Guide
Pin configuration for USB2251-NU-06 (14 x 14 mm package). Pin numbering, functions, and connection diagrams are defined in the manufacturer datasheet. Refer to it for the exact footprint and soldering guidelines.
No detailed pinout data available for USB2251-NU-06.
Refer to the datasheet for full pin configuration.
Typical Applications
USB2251-NU-06 is suitable for 6 applications: USB Flash-Memory Card Reader, Portable Data-Backup Device, Embedded Flash-Storage Adapter, Digital Media Transfer System, Industrial USB Storage Gateway, USB Media Synchronization Device.
USB Flash-Memory Card Reader
The USB2251-NU-06 fits a USB flash-memory reader because it provides a Hi-Speed USB 2.0 host interface and flash-media card controller functionality in one 128-terminal VTQFP package. The 35 Mbps maximum data-transfer rate is suitable for transferring files between a computer and removable flash media, while the 24 MHz maximum clock supports the controller's digital interface. In a reader design, the USB2251 handles USB transactions from the host and exchanges media commands and data with the connected flash device. The 3.3 V supply and dense 0.40 mm-pitch package require careful 3.3 V power distribution and unobstructed routing to all 128 terminals.
Recommended
Portable Data-Backup Device
The USB2251-NU-06 is appropriate for a portable backup appliance that connects flash storage to a USB host and benefits from the controller's 35 Mbps maximum transfer rate. That rate is more than twice the 12 Mbps Full-Speed USB limit and can reduce transfer time for moderate-size backup sessions when both host and media keep the bus active. The controller's integrated USB 2.0 and flash-media interface reduces the need for separate host-interface glue. Designers must still verify the exact supported-media configuration and supply requirements in the manufacturer datasheet before selecting it for a new portable-storage architecture.
Recommended
Embedded Flash-Storage Adapter
The USB2251-NU-06 can serve as the USB-facing controller in an embedded storage adapter that exposes a flash device to a USB host. Its dedicated flash media card controller role, USB 2.0 compatibility, and 24 MHz maximum clock are more directly aligned with this task than with a general-purpose USB interface. The controller may be paired with external flash storage or a compatible removable media interface. PCB implementation must preserve USB impedance and clock timing, while the 3.3 V rail needs low-impedance decoupling close to the device. Verify the exact media protocol and configuration options before freezing the hardware.
Recommended
Digital Media Transfer System
The USB2251-NU-06 fits a digital media transfer system requiring a dedicated Hi-Speed USB 2.0 interface to flash media. Its 35 Mbps maximum transfer rate can improve the movement of photos, audio, or configuration data compared with a Full-Speed USB path, while the dedicated controller architecture offloads USB-media command handling from the system processor. The device is best used where the required card or flash protocol is explicitly supported. The 128-terminal, 0.40 mm-pitch package supports dense integration but demands careful assembly, fine-pitch routing, and accurate package-outline verification.
Recommended
Industrial USB Storage Gateway
The USB2251-NU-06 can be used in an industrial storage gateway that transfers files between a USB host and local flash media. Its 24 MHz maximum clock and 35 Mbps maximum data rate provide defined operating limits for the USB 2.0 storage path, while the dedicated flash-card controller function simplifies the media-facing side of the design. Industrial use still requires checking the operating-temperature and qualification data, neither of which is present in the supplied verified records. The 3.3 V power design should include local bypass and controlled sequencing, and USB traces should use continuous planes without test pads or stubs where signal integrity is sensitive.
Recommended
USB Media Synchronization Device
The USB2251-NU-06 is suitable for a synchronization appliance that copies media files between a computer and flash storage. A 35 Mbps maximum data-transfer rate supports useful throughput for background synchronization and avoids the lower 12 Mbps ceiling of Full-Speed USB. The dedicated flash media controller role can handle the storage-facing transactions while a separate system controller manages application-level synchronization. Timing between the host, storage media, and USB interface must be checked against the family datasheet's AC specifications. Engineers should also account for 3.3 V rail tolerance, fine-pitch assembly capability, and controlled-impedance USB routing.
Recommended
Recommended Products Summary
Engineering reference data for USB2251-NU-06 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | USB2251I-NU-06 | USB2251-NU-05 | USB2250I-NU-06 | USB2250-NU-06 | USB2250-NU-05 |
|---|---|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 128-VTQFP (14x14) | 128-VTQFP (14x14) - same | 128-VTQFP (14x14) - same | 128-VTQFP (14x14) - same | 128-VTQFP (14x14) - same | 128-VTQFP (14x14) - same |
| Controller Family | USB2251 | USB2251I | USB2251 | USB2250I | USB2250 | USB2250 |
| USB Compatibility | USB 2.0 | USB 2.0 flash media interface | USB 2.0 flash media interface | USB 2.0 flash media interface | USB 2.0 flash media interface | USB 2.0 flash media interface |
| Ordering Suffix | -NU-06 | -NU-06 with I-family identifier | -NU-05 | -NU-06 with I-family identifier | -NU-06 | -NU-05 |
Key Differentiators
- Exact target ordering code with verified 35 Mbps maximum data rate (vs USB2251-NU-05)
- Verified 14 x 14 mm, 0.40 mm-pitch 128-terminal package (vs USB2250-NU-06)
- USB 2.0 and I2C bus compatibility documented for the target (vs USB2250I-NU-06)
Design Notes
Route the USB 2.0 differential pair as a short, continuous, impedance-controlled path over a solid reference plane. Avoid stubs, test pads, acute corners, and plane interruptions near the controller. The supplied data confirms a 35 Mbps maximum transfer rate and a 24 MHz maximum clock, but it does not provide trace-impedance or via-geometry values; derive those from the complete USB channel design and the manufacturer reference layout rather than from a generic value.
Do not release the 128-terminal footprint until the exact 14 x 14 mm VTQFP package drawing has been checked against the selected PCB library. The verified terminal pitch is 0.40 mm, which makes assembly and soldering process capability important. Confirm pad dimensions, exposed or non-exposed center-pad requirements, pin numbering, solder-mask clearance, and the manufacturer's recommended land pattern. The package SVG library has no exact 128-terminal TFQFP/VTQFP key, so `default` is used rather than inventing a diagram.
Design a clean 3.3 V supply path with local high-frequency bypassing placed close to the controller's supply terminals. Follow the manufacturer datasheet for the exact pin names, capacitor values, voltage tolerance, and power-up requirements because those details are not included in the supplied web snippets. Check that the 35 Mbps operating mode can be supplied without excessive rail ripple or shared-impedance coupling to adjacent USB or flash-media signals.
Do not treat the USB2250, USB2250I, USB2251, and USB2251I family codes as interchangeable solely because the verified cross-reference pages place them in the same search results. The suffix and I-family identifier may alter supported media, configuration, or device options. Before replacing USB2251-NU-06, compare the numbered pin table, supported-media list, reset behavior, clock requirements, USB descriptors, and package outline for the exact candidate.
Compliance Information
The supplied verified data does not explicitly state compliance for USB2251-NU-06. Compliance fields remain unknown rather than being inferred from generic distributor or family information.
