1-Ch Full-Speed USB UART


The XR21V1410 is an enhanced 1-channel 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 XR21V1410 operates from an internal 48MHz clock therefore no external crystal/oscillator is required like previous generation UARTs. With the fractional baud rate generator, any baud rate can accurately be generated using the internal 48MHz clock.

The large 128-byte Tx FIFO and 384-byte RX FIFO of the XR21V1410 helps to optimize the overall data throughput for various applications. The Automatic Transceiver Direction control feature simplifies both the hardware and software for half-duplex RS-485 applications. The multidrop (9-bit) mode with automatic half-duplex transceiver control feature further simplifies typical multidrop RS-485 applications.

The XR21V1410 operates from a single 2.97 to 3.63 volt power supply and has 5V tolerant inputs.

Software drivers for Windows 2000, XP, Vista, 7, 8, and CE, as well as Linux and Mac are supported for the XR21V1410.
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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  • 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
    • Automatic Hardware (RTS/CTS or DTR/DSR)Flow Control
    • Automatic Software (Xon/Xoff) Flow Control
    • Multidrop mode w/ Auto Half-Duplex Transceiver Control
    • Multidrop mode w/ Auto TX Enable
    • Half-Duplex mode
    • Selectable GPIO or Modem I/O
  • Internal 48 MHz clock
  • Single 2.97-3.63V power supply
  • 5V tolerant inputs
  • 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

Product Change Notification, Revision B to D

Download Software Drivers

Design Tools

Simulation Models
Package Type Vcc Temp Mode Version File
QFN 3.3V Industrial USB 2
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
XR21V141x Linux EEPROM Programming Utility 2.0.0 April 2013
XR21V141x Windows EEPROM Programming Utility December 2012


Pkg Code Details Quantities Dimensions PDF
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

Parts & Purchasing

Part Number Pkg Code RoHS Min Temp Max Temp Status Buy Now Order Samples
XR21V1410IL16-F QFN16 3x3 -40 85 Active
XR21V1410IL16TR-F QFN16 3x3 -40 85 Active
XR21V1410IL-A1-F OBS Suggested:
XR21V1410TR-A1-F OBS Suggested:
XR21V1410-0A-EB Board Active
XR21V1410-0C-EB Board Active
XR21V1410IL-0B-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.

Quality Documents

Additional Quality Documentation may be available, please contact customersupport@exar.com.
Distribution Date Description File
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
09/02/2015 Metal mask change for yield improvement Process change PCN 14-1145-02-1033.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
03/30/2012 XR21V141x Product Change from Rev B to Rev D Product improvement. PCN_12-0305-01-1033.pdf
08/10/2011 Material change and a new assembly & test supplier (ASE, Kunshan). Business consolidation. PCN_11-0724-01-1033.pdf
01/26/2011 Packing / Shipping: Bulk packing change from tray to canister Packing standardization for 3x3mm QFN. PCN_10-1217-01-1033.pdf
08/04/2010 1. Standardize pin #1 orientation in the reel per Attachment A. 2. Standardize # of units per reel per Attachment A. Refer to PCN for more information. Standardization PCN_10-0716-01-1033.pdf

Frequently Asked Questions

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:


Find the icons under Buy Now or Order Samples:


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


Alternatively, you can click on the Order Samples


If the icons are missing, then contact Customer Support.

The best way to determine this is to go to exar.com and type the part into the search function. At or near the top of the results you should see something that looks like

In this example, we looked for XRA1201. When you hover over it, it will turn grey and you can click anywhere in the grey box. This brings you to the product page. For example:


Click on Parts & Purchasing, highlighted in yellow above. The screen changes to:


Notice the status column and the “Show obsolete parts” link:


A legend tells you the definition of the different statuses. Click on the “Show obsolete parts” link to see EOL or OBS part numbers along with the Active part numbers:


Another method to find out if a part is OBS or EOL is to click on SUPPORT:


And then Product Change Notifications


Type the part into the search, and click on one of the part numbers from the drop down menu. Then you can look for the Product Discontinuation Notice, which generally is at the top of the list, for example:


If you see this, it tells you that this particular orderable part has been discontinued and when the last order date is, or was. If you click on the file, then you can view the notice we sent about this if you purchased the part in the recent past. It may also advise of a replacement part. When an orderable part first becomes discontinued, Product Discontinuation Notices are sent are sent to those who have purchased the parts in the recent past, if purchased directly, with a dated opportunity to place a last order.

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 tested for use with USB 2.0 devices.

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”.

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