XR21B1422IL40-0A Datasheet, PDF (1/60 Pages) Exar Corporation – Enhanced 2-Ch Full-Speed USB UART

XR21B1422
Enhanced 2-Ch Full-Speed USB UART
General Description
The XR21B1422 is an enhanced Universal Asynchronous Receiver and
Transmitter (UART) bridge to USB interface. The USB interface is fully
compliant to the USB 2.0 (Full-Speed) specification with 12 Mbps USB
data transfer rate. The USB interface also supports USB suspend,
resume and remote wakeup operations. The USB Vendor ID, Product ID,
power mode, remote wakeup support, maximum power, and numerous
other settings may be programmed in the on-chip OTP memory via the
USB interface.
The XR21B1422 includes an internal oscillator and does not require an
external crystal/oscillator. Any UART baud rate up to 12 Mbps may be
generated with this internal clock and the fractional baud rate generator.
The UART pins for each port may also be configured as GPIO; direction,
state, output driver type and input pull-up or pull-down resistors are pro-
grammed either through on chip OTP, or on the fly via memory mapped
registers.
Large 512-byte TX and RX FIFOs prevent buffer overflow errors and opti-
mize data throughput. Automatic half-duplex direction control and optional
multi drop (9-bit) mode simplify both hardware and software in half-duplex
RS-485 applications.
The XR21B1422 uses the native OS CDC-ACM driver or an Exar supplied
custom driver. Exar provides WHQL/HCK-certified software drivers for
Windows 2000, XP, Vista, 7, 8, 8.1 as well as software drivers for Windows
CE, Linux and Mac OS X. Full source code is available.
The XR21B1422 operates from a single 5V or 3.3V power supply. When
powered with 5V input, a regulated 3.3V output is supplied.
Block Diagram
FEATURES
• ±15kV ESD on USBD+/USBD-
• USB 2.0 Compliant, Full-Speed (12Mbps)
• Unique pre-programmed USB serial number
• Internally generated 48MHz core clock
• Enhanced UART features
• Baud rates up to 12 Mbps
• Fractional Baud Rate Generator
• 512-byte TX and 512-byte RX FIFOs
• Auto Hardware / Software Flow Control
• Multidrop and Half-Duplex Modes
• Auto RS-485 Half-Duplex Control
• Selectable GPIO or Modem I/O
• Up to 10 GPIOs per channel
• 5V tolerant GPIO inputs
• Suspend state GPIO configuration
• Configurable clock output
• 40-pin QFN package
• Industrial -40°C to +85°C Temperature Range
APPLICATIONS
• Building Automation
• Security Systems
• Factory and Process Control
• ATM Terminals
• USB to Serial Controllers
Ordering Information – page 60
Internal
Oscillator
(48MHz)
USB
USB Slave Interface
USB
Descriptors
OTP
Fractional
BRG
512-byte
TX FIFO
512-byte
RX FIFO
Internal
Status and
Control
Registers
GPIOs/
Modem IO
VIO
TX
RX
LDO
UART Ch A
3V3
UART Ch B
(same as Ch A)
1840k
1610k
1380k
1150k
920k
690k
460k
230k
0k
Throughput Comparison
Competitor
Exar
230k
460k
920k
Data Rate (bps)
1840k
© 2014 Exar Corporation
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exar.com/XR21B1422
Rev 1A