XR21B1411

Enhanced 1-CH Full-Speed USB UART
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Overview

Information Enhanced 1-CH Full-Speed USB UART
Data Bus Interface USB 2.0
# of Channels 1
Max Data Rate 5V (Mbps) 12
Max Data Rate 3.3V (Mbps) na
Tx FIFO (Bytes) 128
Rx FIFO (Bytes) 384
Auto RS-485 ✔
Auto Flow Control ✔
Auto Half-Duplex Control ✔
Multidrop (9-bit) Mode ✔
Fractional Baud Rate Generator ✔
Power Down Mode ✔
5V Tolerant Inputs
IrDA Sup
Supply Voltage Range VCC (V) 4.4 to 5.25
Max UART/GPIO Input Voltage (V) 5.5
Max UART/GPIO Output Voltage (V) 1.6-3.6
Temperature Range (°C) -40 to 85
Package QFN-16
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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.

  • ±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


Documentation & Design Tools

All Types Data Sheets Application Notes Schematics & Design Files Product Briefs & Brochures Software & Utilities User Guides & Manuals
Type Title Version Date File Size
Data Sheets XR21B1411 Enhanced 1-ch Full-Speed USB UART 1.2.3 May 2023 1.4 MB
Application Notes DAN-190, MaxLinear UARTs in RS-485 Applications R01 July 2023 2.4 MB
Application Notes AN202, USB UART Board Design Considerations for USB Compliance R02 June 2023 2.4 MB
Application Notes AN-226, Windows Driver Customization for USB UARTs R00 February 2020 2.5 MB
Application Notes AN217, Enumerating the XR21B1411 USB UART by Location in Windows 1.0.0 August 2012 127.6 KB
Application Notes AN205, Comparison of the XR21V1410 and the XR21B1411 1.0.0 March 2011 215.8 KB
Application Notes AN213, USB Basics for the MaxLinear Family of USB UARTS 1.0.0 March 2011 107.3 KB
User Guides & Manuals XR21B14xx_XR21V14xx USB UART Design Guide 01 May 2020 2.3 MB
Software: GUIs & Utilities Sample USB UART GUI (Serial Test App) 1.2.0.0 July 2021 1.4 MB
Software: GUIs & Utilities Android Application 1C November 2015 476.6 KB
Product Flyers Full-Speed USB UART Family 1.1 November 2020 605.3 KB
Product Flyers Enhanced 1-CH Full-Speed USB UART September 2010 737.5 KB
Software: Drivers Linux 3.6.x and Newer 1G August 2024 29.7 KB
Software: Drivers Windows 10 and newer 2.7.0.0 January 2023 169.2 KB
Software: Drivers Windows 7, 8 2.6.0.0 December 2019 145.7 KB
Software: Drivers XRUSB1 for Win XP SP3 and newer 2.2.5.0 March 2016 1 MB
Software: Drivers Linux 2.6.18 to 3.4.x 1A January 2015 19.1 KB
Software: Drivers Mac 1.0.4 October 2013 171.3 KB
Product Brochures Serial Transceivers & Bridges Brochure R03 May 2025 3.6 MB
Schematics & Design Files XR21B1411-0A-EB Evaluation Board Schematics & Design Files 1.0.0 May 2011 676.5 KB
Register for a myMxL account or Login to myMxL to view all Technical Documentation & Design Tools.

Quality & RoHS

Part Number RoHS | Exempt RoHS Halogen Free REACH TSCA MSL Rating / Peak Reflow Package
XR21B1411IL16-F N Y Y Y Y L1 / 260ᵒC QFN16 3x3
XR21B1411IL16TR-F N Y Y Y Y L1 / 260ᵒC QFN16 3x3

Click on the links above to download the Certificate of Non-Use of Hazardous Substances.

Additional Quality Documentation may be available, please Contact Support.

Parts & Purchasing

Part Number Pkg Code Min Temp Max Temp Status Suggested Replacement Buy Now Order Samples PDN
XR21B1411IL16-B1-F QFN16 3x3 OBS XR21B1411IL16-F
XR21B1411IL16-B2-F QFN16 3x3 OBS XR21B1411IL16-F
XR21B1411IL16-F QFN16 3x3 -40 85 Active Order
XR21B1411IL16TR-F QFN16 3x3 -40 85 Active Order
XR21B1411ILTR-B1-F QFN16 3x3 OBS XR21B1411IL16TR-F
XR21B1411IL-0A-EB Board Active
Show obsolete parts
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.

Packaging

Pkg Code Details Quantities Dimensions
QFN16 3x3
  • JEDEC Reference: MO-220
  • MSL Pb-Free: L1 @ 260ºC
  • MSL SnPb Eutectic:
  • ThetaJA: 36.4ᵒC
  • Bulk Pack Style: Tray
  • Quantity per Bulk Pack: 490
  • Quantity per Reel: 3000
  • Quantity per Tube: n/a
  • Quantity per Tray: 490
  • Reel Size (Dia. x Width x Pitch): 330 x 12 x 8
  • Tape & Reel Unit Orientation: Quadrant 1
  • Dimensions: mm
  • Length: 3.0
  • Width: 3.0
  • Thickness: 1.00
  • Lead Pitch: 0.5

Notifications

Distribution Date Description File
07/17/2023 In 2023, MaxLinear will be converting all shipping labels for the parts noted from an EXAR format to MaxLinear’s label. During this transition customers may receive either label. This change affects only shipping and packing labels. This change will not affect the part number, part marking, manufacturing process or manufacturing sites. Only work in progress material will be converted. Existing inventory from MaxLinear’s warehouse, channel sales, distributor, and such, will not be converted. Hence, customers may experience receiving mixed shipments with both Exar and MaxLinear labels for some period until existing inventory of old labels is eventually cleared out. Situation is product to product with no predictable way to determine when all old labels will be exhausted. No change to product form, fit, function and reliability. ADDENDUM A: Fixed MBB label logo for DX204001 to MaxLinear logo. ADDENDUM B: Replaced ‘All other affected products outer box label’ with clearer pictures. Corrected Date Issued (from original PCN) issue date +90 days to August 30, 2023.
06/01/2023 In 2023, MaxLinear will be converting all shipping labels for the parts noted from an EXAR format to MaxLinear’s label. During this transition customers may receive either label. This change affects only shipping and packing labels. This change will not affect the part number, part marking, manufacturing process or manufacturing sites. Only work in progress material will be converted. Existing inventory from MaxLinear’s warehouse, channel sales, distributor, and such, will not be converted. Hence, customers may experience receiving mixed shipments with both Exar and MaxLinear labels for some period until existing inventory of old labels is eventually cleared out. Situation is product to product with no predictable way to determine when all old labels will be exhausted. No change to product form, fit, function and reliability.
06/01/2023 In 2023, MaxLinear will be converting all shipping labels for the parts noted from an EXAR format to MaxLinear’s label. During this transition customers may receive either label. This change affects only shipping and packing labels. This change will not affect the part number, part marking, manufacturing process or manufacturing sites. Only work in progress material will be converted. Existing inventory from MaxLinear’s warehouse, channel sales, distributor, and such, will not be converted. Hence, customers may experience receiving mixed shipments with both Exar and MaxLinear labels for some period until existing inventory of old labels is eventually cleared out. Situation is product to product with no predictable way to determine when all old labels will be exhausted. No change to product form, fit, function and reliability. ADDENDUM: Fixed MBB label logo for DX204001 to MaxLinear logo.
01/12/2021 Product Discontinuation Notice
07/04/2018 Product Discontinuation Notice
07/11/2017 Product Discontinuation Notification
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.
02/14/2017 Qualification of alternate assembly subcon, GREATEK, Taiwan.
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.
01/27/2017 Qualification of alternate assembly subcon, ANST, China.
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.
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.
10/03/2013 Product Discontinuation Notification Discontinued.
08/10/2011 Material change and a new assembly & test supplier (ASE, Kunshan). Business consolidation.

FAQs & Support

Search our list of FAQs for answers to common technical questions.
For material content, environmental, quality and reliability questions review the Quality tab or visit our Quality page.
For ordering information and general customer service visit our Contact Us page.

Submit a Technical Support Question As a New Question

For some UARTs, Microsoft certified drivers are available for Windows Operating System and can be downloaded via Windows Update. These drivers and others, including for Linux and other Operating Systems can be found by visiting https://www.exar.com/design-tools/software-drivers Please note Software Driver Use Terms.

 

 
You can also get to this link by going to the exar.com website, clicking on Support (in black bar near top of page), then click on Design Tools, then under Evaluation Hardware and Software (towards right of page) click on Software Drivers.
 
 

Click on the version link under Driver Version of the desired type of UART, part number and operating system. A zip file is downloaded which contains a ReadMe file with instructions.

Links to datasheets and product family pages are in the software driver table for easy reference. 

No, Auto RTS and Auto CTS are independent. Auto RTS is toggled by the UART receiver. Auto CTS is monitored by the UART Transmitter.

No, Auto RTS and Auto CTS will work normally without the interrupts enabled.

No, software flow control characters are not loaded into the RX FIFO.

Auto RS485 Half-Duplex Control feature overrides the Auto RTS flow control feature if both features use the RTS# output pin. Both features can only be used simultaneously if the Auto RS485 control output is not the RTS# output. For some UARTs, the Auto RS485 control output is not the RTS# output.

The polarity of the RS485 control output varies from one UART to another. For some UARTs, an inverter may be required. Some of the newer UARTs have register bits that can change that polarity of the RS485 control output.

All of the UARTs that have the IR mode supports up to 115.2Kbps as specified in IrDA 1.0. The newer I2C/SPI UARTs can support up to 1.152Mbps as specified in IrDA 1.1.

Find the product page of the part that you want to get an evaluation board for and click on Parts & Purchasing. Example:


Product Page - Top Section


Click on Parts & Purchasing or Order Now. Locate the icons under Buy Now or Order Samples:

 

Parts & Purchasing section on Product Page


Click on the Buy Now icon and see who has stock and click on the Buy button:

 

Buy Now Button result - Purchase Parts Window

 

Alternatively, you can click on the Order Samples icon to request a sample.


Note, not all products are sampleable from the website.

 

Example of product with no sample or buy now icons

 

If the icons are missing, create a support ticket.

The -F suffix indicates ROHS / Green compliance:
https://www.exar.com/quality-assurance-and-reliability/lead-free-program

Visit the product page for the part you are interested in.  The part's status is listed in the Parts & Purchasing section.  You can also view Product Lifecycle and Obsolescence Information including PDNs (Product Discontinuation Notifications).

 

To visit a product page, type the part into the search window on the top of the MaxLinear website.

 

In this example, we searched for XR33180.  Visit the product page by clicking the part number or visit the orderable parts list by clicking "Orderable Parts". 

 

XR33180 Search Result

 

  

The Parts & Purchasing section of the product page shows the Status of all orderable part numbers for that product.  Click Show obsolete parts, to see all EOL or OBS products.

 

 Show Obsolete parts to expand the list

Connect the USB data pins directly to the host or upstream hub. Connections should be impedance controlled to 90 ohms differential with short traces and no stubs. Connecting any other components that are not high impedance (series or shunt resistance, capacitance or inductance) will corrupt the USB data signaling and can prevent communication between the host and device. ESD protection diodes may be used and some EMI filters may also have only a slight impact on impedance but should be demonstrated for compliance with USB 2.0 devices. See Application Notes AN202 (USB UART Board Design Recommendations and Considerations for USB Compliance), section 2.0 Design Considerations  for more. 

1. Native drivers: Native drivers may be found in all major OS such as Windows, Linux, and Max OSX. Typically these drivers will be automatically loaded. In some cases, these are basic drivers and may have limitations on advanced device functionality, however. USB HID, Hub and CDC-ACM drivers are examples of native drivers. The CDC-ACM driver be used with our CDC-ACM class USB UARTs, but has limited functionality.

 

2. MaxLinear custom drivers: MaxLinear custom drivers may be used to support additional functionality in MaxLinear devices. For example, the MaxLinear custom driver for USB UARTs overcomes the limitations of the native CDC-ACM driver. See https://www.exar.com/design-tools/software-drivers for a list of and access to the drivers that we currently have. In some cases, the MaxLinear driver can also be customized, or source code can be provided after executing a Software License Agreement.

Yes: Go to the product page (XR22804 example below), click on the documentation tab on left, click on “Sample USB UART GUI” under Software:

 

It depends on the baud rate. For example, for a start bit, 8 data bits, no stop bit and 1 stop bit, the maximum baud rate deviation is 4.76%. For more information, see https://www.exar.com/appnote/dan108.pdf

Most UARTs use RTS#, however in addition to using the RTS# output as the Auto RS485 control output, the XR21B1420/1421/1422/1424 can use the DTR# output as the Auto RS485 control output.

The following lines of code must be modified in the xr_usb_serial_hal.c file in the xr_usb_serial_set_flow_mode function at the end of the function:

 

Change from:

xr_usb_serial_set_reg(xr_usb_serial, xr_usb_serial->reg_map.uart_flow_addr, flow);

xr_usb_serial_set_reg(xr_usb_serial, xr_usb_serial->reg_map.uart_gpio_mode_addr, gpio_mode);

 
For active low TX, change to:

xr_usb_serial_set_reg(xr_usb_serial, xr_usb_serial->reg_map.uart_flow_addr, 0x0);

xr_usb_serial_set_reg(xr_usb_serial, xr_usb_serial->reg_map.uart_gpio_mode_addr, 0x3);

 

For active high TX, change to:

xr_usb_serial_set_reg(xr_usb_serial, xr_usb_serial->reg_map.uart_flow_addr, 0x0);

xr_usb_serial_set_reg(xr_usb_serial, xr_usb_serial->reg_map.uart_gpio_mode_addr, 0xB);

All of MaxLinear / Exar's USB UARTs are CDC class / CDC-ACM compliant, except for XR21B1421 which is an HID class device. This means they can use a native CDC driver. All major OS have native CDC drivers, except Windows prior to Windows 10.

None of the MaxLinear / Exar USB UARTs require their custom driver, however they will have certain limitations when not using it. The native CDC driver is not capable of accessing the internal memory map of any device. As a result, when using the native CDC driver, the device “defaults” to a particular configuration. The main implications of this default configuration are that hardware RTS/CTS flow control is enabled and that other settings / advance settings are not configurable. Some devices, for example the XR21B1411 which has an internal OTP memory, can be programmed to change this default configuration, but the configuration cannot be changed “on the fly”.

1.  Enter root privileges: sudo -i
2.  Enter admin password.
3.  Edit /etc/modules file.  Append xr_usb_serial_common to the end of the file.
4.  Build the Exar/MxL driver from the folder using "make", confirm that the xr_usb_serial_common.ko file is successfully created.
5.  Run command: uname -r
This will return the kernal version currently in use. 
6.  Copy the resulting xr_usb_serial_common.ko to /lib/modules/2.6.38.8-generic in the above path with the kernal version that was returned in step 5.
7.  Run depmod.
8.  Reboot. 
9.  Connect the Exar/MxL USB UART.  Using ls/dev/tty* confirm /dev/ttyUSBn ports (Exar driver loaded) for Exar/MxL USB UART.
10. Connect another CDC device (not Exar/MxL), and confirm both /dev/ttyUSBn and /dev/ACMn ports. 

The maximum allowed bus-powered suspend current is 2.5mA per device function. The device function may not be the same as the IC, as there may be multiple device functions per IC. See the individual datasheet for a list of device functions. For example, the XR22804 has 8 device functions: an embedded hub, the Ethernet MAC and Phy, 4 UARTs, I2C controller and EDGE controller. Therefore, the XR22804 maximum allowed bus-powered suspend current is 8 x 2.5mA or 20mA. However, power used by all supporting XR22804 external components that use power from the USB host VBUS power must be included in the suspend current.

It is recommended, especially when connecting a USB cable to the VBUS 5V source.  See Application Note AN202 (USB UART Board Design Recommendations and Considerations for USB Compliance), section 2.2.2 In-rush Current for more.

The OTP can be programmed to modify various USB configuration descriptors such as Vendor ID, Product ID, Device Attributes and maximum power consumption. See Application Note AN202 (USB UART board Design Considerations for USB Compliance), section 2.3 External EEPROM or on-chip OTP for more. The OTP can also be programmed to change default register values, which can be found in the individual datasheets.

Once enumeration is completed, the host and device may carry out data transfers. Four type of data transfers are defined: control, bulk data transfers, interrupts and Isochronous data transfers. Although USB UARTs do support the control, bulk data transfers and interrupts, they do not support Isochronous data transfers which would be needed for applications streaming audio or video. See Application Note AN213 (section 3.3.2) for a description of each.

Videos

English Chinese
 

MxL UARTs Auto RS-485 Direction Control

This video describes how the automatic RS-485 half-duplex direction control feature in MaxLinear UARTs reduces driver development and frees up CPU/MCU loading. This feature eliminates the need to monitor the status of the UART’s transmit shift register and automatically switches MaxLinear RS-485 transceivers from the transmit mode to the receive mode. This video summarizes the content in application note DAN-190. 

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