RS232/RS485/RS422 Transceiver with Internal Termination


The SP339 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 Human Body Model (HBM) and ±8kV IEC-61000-4-2 Contact. 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 5kΩ pull-down to ground. The RS-485/422 receiver inputs are high impedance (>96kΩ when termination is disabled), allowing up to 256 devices on a single communication bus (1/8th unit load).

The SP339E 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.

For technical support or help choosing a product please email Exar’s Serial Technical Support group at:  serialtechsupport@exar.com.

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  • 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 SP338E


  • Dual Protocol Serial Ports (RS-232 or RS-485/422)
  • Industrial Computers
  • Industrial and Process Control Equipment
  • Point-Of-Sale Equipment
  • Networking Equipment
  • HVAC Controls Equipment
  • Building Security and Automation Equipment

Design Tools

Simulation Models
Evaluation Hardware and Software


Pkg Code Details Quantities Dimensions PDF
QFN40 6x6
  • JEDEC Reference: MO-220
  • MSL Pb-Free: L3 @ 260ºC
  • MSL SnPb Eutectic: n/a
  • ThetaJA: 32.3ºC/W
  • Bulk Pack Style: Tray
  • Quantity per Bulk Pack: n/a
  • Quantity per Reel: 3000
  • Quantity per Tube: n/a
  • Quantity per Tray: 490
  • Reel Size (Dia. x Width x Pitch): 330 x 16 x 12
  • Tape & Reel Unit Orientation: Pin 1 at sprocket hole.
  • Dimensions: mm
  • Length: 6.00
  • Width: 6.00
  • Thickness: 0.90
  • Lead Pitch: 0.50

Parts & Purchasing

Part Number Pkg Code RoHS Min Temp Max Temp Status Buy Now Order Samples
SP339ECR1-L QFN40 6x6 0 70 Active
SP339ECR1-L/TR QFN40 6x6 0 70 EOL Suggested:
SP339EER1-L QFN40 6x6 -40 85 Active
SP339EER1-L/TR QFN40 6x6 -40 85 Active
SP339EER1-0A-EB Board Active
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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.
Distribution Date Description File
07/11/2017 Product Discontinuation Notification PDN_17-0626-02-1033.pdf
01/05/2017 Addition of an alternate qualified location, ANST, China. PCN 16-0835-01 ANST-1033.pdf
01/13/2015 Material Change. Qualified copper wire bonding assembly in addition to currently qualified gold wire bonding assembly in Unisem, Ipoh. PCN_14-1249-03-1033.pdf
01/25/2013 The ESD performance of the die has been improved to pass ± 15KV air gap discharge model, as specified by IEC-61000-4-2. The ESD tolerance of the non-bus pins has also been increased from ±2kV to ±4kV HBM (Human Body Model). The Exar product datasheet has been revised to include these improved ratings. There are no other changes to Form, Fit, or Function, as per the applicable datasheets. To improve product performance. PCN_12-1009-01-1033.pdf