XR21B1420 Datasheet, PDF (1/60 Pages) Exar Corporation – Enhanced 1-Ch Full-Speed USB UART

XR21B1420
Enhanced 1-Ch Full-Speed USB UART
General Description
The XR21B1420 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 XR21B1420 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 may also be configured as GPIO; direction, state, output
driver type and input pull-up or pull-down resistors are programmed 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 XR21B1420 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 XR21B1420 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
 5V tolerant GPIO inputs
 Suspend state GPIO configuration
 Configurable clock output
 28-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
USB
Internal
Oscillator
(48MHz)
USB Slave Interface
USB
Descriptors
OTP
Fractional
BRG
512-byte
TX FIFO
512-byte
RX FIFO
Internal
Status and
Control
Registers
GPIOs/
Modem IO
UART
LDO
3V3
TX
1840k
Throughput Comparison
1610k
RX
1380k
Competitor
Exar
1150k
920k
690k
460k
230k
0k
230k
460k
920k
Data Rate (bps)
1840k
© 2014 Exar Corporation
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exar.com/XR21B1420
Rev 1A