NXP Semiconductors USB2SERA11CFK

Overview

USB2SERA11CFK from Freescale Semiconductor is a USB 2.0 Full-Speed (12 Mbps) to UART bridge IC in a 5 × 5 mm, 24-pin QFN package. It integrates a USB transceiver, UART engine, 3.3 V regulator, and PLL-based clock multiplier (2–48 MHz), supporting RS232 or RS485 interface with hardware/software flow control, programmable baud rates (300–115200 bps), and configurable VID/PID strings for embedded serial connectivity.

For engineers reviewing the USB2SERA11CFK datasheet, USB2SERA11CFK pinout, USB2SERA11CFK application, or USB2SERA11CFK equivalent, this page delivers verified technical context, real-world UART-to-USB integration constraints, supply voltage dependencies (3–5 V), suspend/resume signaling behavior, and factory-configurable descriptors - all critical for industrial gateway, legacy device modernization, and certified Windows/Linux COM port deployment.

Technical Context

The USB2SERA11CFK implements a CDC-compliant USB 2.0 Full-Speed device with integrated 3.3 V regulator and auto-detecting Pierce oscillator (2/4/6/8/12/16 MHz crystal support). Its UART supports 8-bit data, 1–2 stop bits, odd/even/no parity, and adjustable receive buffer timeout (1–99 ms).

It features dual activity indicators (USB_LED, UART_LED), RS485_TXEN control, hardware RTS/CTS flow control, and software Xon/Xoff support. Reset sources include Power-On Reset, external /RESET, and soft reset; system initialization includes 48 ms crystal auto-detection followed by PLL lock to 48 MHz for synchronized USB and UART timing.

Key Specifications

Pinout & Package

USB2SERA11CFK is housed in a RoHS-compliant, lead-free 24-pin QFN package (5 × 5 mm, Case 1897) with exposed thermal pad. Pin 1 is marked by a dot; pin numbering follows standard counter-clockwise convention from top-left corner.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar USB-to-UART bridge applications.

Compared with CP2102N-A02-GM and FT232RL, USB2SERA11CFK uniquely combines RS485_TXEN control, integrated 3.3 V regulator, crystal auto-detection, and password-secured flash configuration - making it optimal for industrial field devices requiring robust, certified, and field-upgradable serial bridging without external components.

Availability

USB2SERA11CFK is available at Aetrix Electronics and suitable for industrial HMI terminals, legacy equipment retrofit, and embedded Linux gateway designs requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant QFN packaging.

Supply support for USB2SERA11CFK includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Freescale Semiconductor (now part of NXP Semiconductors) is a global leader in embedded processing solutions, specializing in automotive, industrial, and networking microcontrollers and interface ICs.

USB2SERA11CFK belongs to Freescale's Ready Play Solutions product line - designed specifically for certified, low-risk integration of USB connectivity into resource-constrained embedded systems with minimal firmware overhead and zero driver development.

FAQ

What is the maximum UART baud rate supported by USB2SERA11CFK?

USB2SERA11CFK supports a maximum UART baud rate of 115200 bps. This is the default post-reset configuration and represents the upper limit of its internal clock divider design. At this rate, the device achieves ±0.5% typical accuracy using its 48 MHz PLL-derived clock source. Higher rates are not supported due to timing constraints in the UART engine and USB bulk transfer framing.

Does USB2SERA11CFK require an external crystal, and what frequencies are supported?

Yes, USB2SERA11CFK requires an external crystal connected between XTAL and EXTAL pins. It supports 2 MHz, 4 MHz, 6 MHz, 8 MHz, 12 MHz, and 16 MHz crystals in Pierce oscillator configuration. The device performs automatic frequency detection during power-up initialization (48 ms duration), eliminating manual configuration or firmware calibration.

Can USB2SERA11CFK operate with a 3.3 V supply only, or does it require 5 V?

USB2SERA11CFK operates from a single 3.0–5.5 V supply on VDD. When powered from 3.3 V, the internal 3.3 V regulator is bypassed and VUSB33 must not be connected to an external source. When powered from 3.9–5.0 V, the internal regulator activates to supply the USB PHY - enabling full USB compliance without external regulators or level shifters.

How is RS485 half-duplex operation implemented using USB2SERA11CFK?

RS485 half-duplex operation is implemented using the dedicated RS485_TXEN pin (Pin 8), which drives the DE/RE control inputs of an external RS485 transceiver (e.g., SP3485). The pin is asserted high during UART transmit and de-asserted low during receive, ensuring correct bus direction control without software intervention or timing-critical GPIO toggling.

Is USB2SERA11CFK certified for Windows operating systems, and which versions are supported?

Yes, USB2SERA11CFK is certified under the Windows Logo Program for Windows Vista and Windows 7. Its drivers support Windows XP (32/64-bit), Vista (32/64-bit), and Windows 7 (32/64-bit). The device enumerates as a standard CDC ACM class device, enabling plug-and-play COM port functionality on Windows 10/11 via inbox drivers - though advanced features like flow control require Freescale's signed custom drivers.