Enhanced 1-CH Full-Speed USB UART


The XR21B1411 (B1411) is an enhanced Universal Asynchronous Receiver and Transmitter (UART) with a USB interface. The USB interface is fully compliant to Full Speed USB 2.0 specification that supports 12 Mbps USB data transfer rate. The USB interface also supports USB suspend, resume and remote wakeup operations.

The B1411 operates from an internal clock that is programmable to 6, 12, 24 or 48 MHz. Therefore, no external crystal / oscillator is required as in previous generation UARTs. With the fractional baud rate generator, any baud rate up to 12 Mbps can be accurately generated using the internal clock.

The large 128-byte TX FIFO and 384-byte RX FIFO of the B1411 help to optimize the overall data throughput for various applications. The Automatic Transceiver Direction control feature simplifies both the hardware and software for halfduplex RS-485 applications. If required, the multidrop (9-bit) mode with automatic half-duplex transceiver control feature further simplifies typical multidrop RS-485 applications.

The Vendor ID, Product ID, bus-powered mode, self-powered mode, remote wakeup support or maximum power consumption values, as well as default baud rate settings can be programmed using the on-board OTP through the USBD+ / USBD- pins.

The B1411 operates from a single 5V power supply and is available in a 16-pin QFN package.

Software drivers for Windows 2000, XP, Vista, 7, 8, and CE, as well as Linux and Mac are supported for the XR21B1411.


For UART technical support or to obtain an IBIS model for this product, please email Exar's UART Technical Support group.

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  • ±15kV HBM ESD on USBD+/USBD-
  • USB 2.0 Compliant Interface
    • Supports 12 Mbps USB full-speed data rate 
    • Supports USB suspend, resume and remote wakeup operations
  • Enhanced UART Features
    • Data rates up to 12 Mbps
    • Fractional Baud Rate Generator
    • 128 byte TX FIFO
    • 384 byte RX FIFO
    • 7, 8 or 9 data bits
    • 1 or 2 stop bits 
    • Odd, even, mark, space or no parity
    • Automatic Hardware (RTS/CTS or DTR/DSR) Flow Control
    • Automatic Software (Xon/Xoff) Flow Control
    • Multidrop mode 
    • Auto Transceiver Control 
    • Half-Duplex mode 
    • Selectable GPIO or Modem I/O
  • Internal 48 MHz clock with clock divisors programmable down to 6 MHz
  • Single 5V power supply
  • 16-pin QFN package
  • Virtual COM Port Drivers
    • Windows 2000, XP, Vista, 7, and 8
    • Windows CE 4.2, 5.0, 6.0, and 7.0
    • Linux
    • Mac


  • Portable Appliances
  • External Converters (Dongles)
  • Battery-Operated Devices
  • Cellular Data Devices
  • Factory Automation and Process Controls
  • Industrial Applications

Download Software Drivers

Design Tools

Evaluation Hardware and Software
Operating System Driver Version Release Date File
Linux 3.6.x and Newer 1C January 2017
Windows XP, Vista, 7, 8 March 2016
Android Application 1C November 2015
Windows XP, Vista, 7, 8, 8.1, 10 August 2015
Linux 2.6.18 to 3.4.x 1A January 2015
Sample USB UART GUI December 2013
Mac 1.0.4 October 2013
OTP Programming Tool February 2013


Pkg Code Details Quantities Dimensions PDF
QFN16 3x3 OPT1
  • JEDEC Reference: MO-220
  • MSL Pb-Free:
  • MSL SnPb Eutectic:
  • ThetaJA:
  • Bulk Pack Style:
  • Quantity per Bulk Pack:
  • Quantity per Reel:
  • Quantity per Tube:
  • Quantity per Tray:
  • Reel Size (Dia. x Width x Pitch):
  • Tape & Reel Unit Orientation:
  • Dimensions:
  • Length: 3.0
  • Width: 3.0
  • Thickness: 0.9
  • Lead Pitch:

Parts & Purchasing

Part Number Pkg Code RoHS Min Temp Max Temp Status Buy Now Order Samples
XR21B1411IL16-B1-F OBS Suggested:
XR21B1411IL16-B2-F OBS Suggested:
XR21B1411IL16-F QFN16 3x3 OPT1 -40 85 Active
XR21B1411IL16TR-F QFN16 3x3 OPT1 -40 85 Active
XR21B1411ILTR-B1-F OBS Suggested:
XR21B1411IL-0A-EB Board Active
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Part Status Legend
Active - the part is released for sale, standard product.
EOL (End of Life) - the part is no longer being manufactured, there may or may not be inventory still in stock.
CF (Contact Factory) - the part is still active but customers should check with the factory for availability. Longer lead-times may apply.
PRE (Pre-introduction) - the part has not been introduced or the part number is an early version available for sample only.
OBS (Obsolete) - the part is no longer being manufactured and may not be ordered.
NRND (Not Recommended for New Designs) - the part is not recommended for new designs.
Distribution Date Description File
07/11/2017 Product Discontinuation Notification Product Discontinuation Notice 17-0623-02 r-1033.pdf
06/29/2017 Unify Package 16L 3X3 QFN lead length (L) range from 0.35-0.45 mm to 0.30-0.50 mm and add Pin1 indication. PCN 17-0623-01-1033.pdf
02/14/2017 Qualification of alternate assembly subcon, GREATEK, Taiwan. PCN 17-0102-01 Greatek-1033.pdf
01/31/2017 Addition of qualified 12 inch wafer processing line in Global Foundries, in addition to the currently qualified 8 inch wafer processing. Note: Reliability report will be available February 17, 2017. PCN 16-0731-01-01 12 inch Global Foundries-1033.pdf
01/27/2017 Qualification of alternate assembly subcon, ANST, China. PCN 16-1145-04-01 ANST-1033.pdf
05/16/2016 XR21B1411C has been qualified and production released. Rev C has improved USB differential noise performance, replacing Rev B as production. The products listed above are affected. Switchover will be identified by date code. PCN 16-0519-01-01-1033.pdf
04/02/2014 Qualified UTAC Thailand for assembly using copper wire or gold wire bonding assembly, in addition to the current qualified gold wire bonding assembly sites, Unisem Batam and UTAC China. Material change and alternate assembly site. PCN_13-0729-02-1033.pdf
10/03/2013 Product Discontinuation Notification Discontinued. PDN_13-1003-01-1033.pdf
08/10/2011 Material change and a new assembly & test supplier (ASE, Kunshan). Business consolidation. PCN_11-0724-01-1033.pdf