RS-232/RS-485/RS-422 TRANSCEIVER WITH INTERNAL TERMINATION
The SP339B is an advanced multiprotocol
transceiver supporting RS-232, RS-485, and RS-422
serial standards in a 40 pin QFN package. Integrated
cable termination and four configuration modes allow
all three protocols to be used interchangeably over a
single cable or connector with no additional switching
components. Full operation requires only four
external charge pump capacitors.
The RS-485/422 modes feature one driver and one
receiver (1TX/1RX) in both half and full duplex
configurations. The RS-232 mode (3TX/5RX)
provides full support of all eight signals commonly
used with the DB9 RS-232 connector. A dedicated
diagnostic loopback mode is also provided.
The high speed drivers operate up to 20Mbps in RS-
485/422 modes, and up to 1Mbps in RS-232 mode.
All drivers can be slew limited to 250kbps in any
mode to minimize electromagnetic interference (EMI).
All transmitter outputs and receiver inputs feature
robust electrostatic discharge (ESD) protection to
±15kV IEC-61000-4-2 Air Gap, ±8kV IEC-61000-4-2
Contact, and ±15kV Human Body Model (HBM).
Each receiver output has full fail-safe protection to
avoid system lockup, oscillation, or indeterminate
states by defaulting to logic-high output level when
the inputs are open, shorted, or terminated but
undriven. No external biasing resistors are required.
The RS-232 receiver inputs include a 5k pull-down
to ground. The RS-485/422 receiver inputs are high
impedance (>96k when termination is disabled),
allowing up to 256 devices on a single
communication bus (1/8th unit load).
The SP339B operates from a single power supply,
either 3.3V or 5V, with low idle current (2mA typical in
all modes). The shutdown mode consumes less than
10µA for low power standby operation.
Rx enabled during Tx short circuit condition
Pin selectable Cable Termination
No external resistors required for RS-485/422
termination and biasing
3.3V or 5V Single Supply Operation
Robust ESD Protection on bus pins
±15kV IEC 61000-4-2 (Air Gap)
± 8kV IEC 61000-4-2 (Contact)
±15kV Human Body Model (HBM)
Max Data Rate of 20Mbps in RS-485/422 Modes
and up to 1Mbps in RS-232 Modes
Pin selectable 250kbps Slew Limiting
3 Drivers, 5 Receivers RS-232/V.28
1 Driver, 1 Receiver RS-485/422
Full and Half Duplex Configuration
1/8th Unit Load, up to 256 receivers on bus
RS-485/422 Enhanced Failsafe for open, shorted,
or terminated but idle inputs
Space saving 6mm x 6mm QFN-40 Package
Pin compatible with SP339E and SP338E
Dual Protocol Serial Ports (RS-232 or RS-485/422)
Industrial and Process Control Equipment
HVAC Controls Equipment
Building Security and Automation Equipment
NOTE: -L = Green / RoHS Compliant, /TR = Tape and Reel
OPERATING TEMPERATURE RANGE
-40°C to +85°C
-40°C to +85°C
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • (510) 668-7000 • FAX (510) 668-7017 • www.exar.com