RS232/RS485/RS422 Transceiver with Internal Termination
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Information RS-232/RS-485/RS-422 Transceiver with Internal Termination
Supported Protocols RS232, V.28, RS485, RS422, V.24
Supply Voltage (Nom) (V) 3.3, 5
232 Tx / Rx 3 / 5
485 Tx / Rx 1 / 1
RS-232 Max Data Rate (Mbps) 1
RS-485/RS-422 Max Data Rate (Mbps) 20
HBM ESD (kV) 15
IEC 61000-4-2 Contact (±kV) 8
120Ω Termination
VL Pin
232 Full Handshake
Slew Limit Pin
Fault Tolerance (V) -18 to 18
RS-485 Duplex Half/Full
Max ICC (mA) 8
Temperature Range (°C) 0 to 70, -40 to 85
Package QFN-40
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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.

  • 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

Documentation & Design Tools

Type Title Version Date File Size
Data Sheets RS-232/RS-485/RS-422 Transceiver with Internal Termination 1.0.7 May 2020 1.9 MB
Application Notes Advantages of Designing with Multi-Protocol Transceivers Application Note R00 September 2023 2.5 MB
Application Notes DAN-190, MaxLinear UARTs in RS-485 Applications R01 July 2023 2.4 MB
Application Notes RS-232 and RS-485 PCB Layout Application Note R00 December 2022 2.8 MB
Application Notes ANI-22, Enhanced Receiver Failsafe Implementation In Dual Protocol SP339 and XR34350 Serial Transceivers January 2017 916.8 KB
User Guides & Manuals XR21B1420 Evaluation Board User’s Manual 1B January 2020 1.2 MB
Product Brochures Interface Brochure November 2023 3.7 MB
Schematics & Design Files XR21B1420/1421 Evaluation Board Design Files REV 10 June 2016 386.5 KB
Simulation Models
Package Type Vcc Temp Mode Version File
QFN-40 3.3V Industrial 00 2
QFN-40 3.3V Industrial 01 2
QFN-40 3.3V Industrial 10 1
QFN-40 3.3V Industrial 11 1
QFN-40 5.0V Industrial 00 1
QFN-40 5.0V Industrial 01 1
QFN-40 5.0V Industrial 10 1
QFN-40 5.0V Industrial 11 1
QFN-40 3.3V Commercial 00 1
QFN-40 3.3V Commercial 01 1
QFN-40 3.3V Commercial 10 1
QFN-40 3.3V Commercial 11 1
QFN-40 5.0V Commercial 00 1
QFN-40 5.0V Commercial 01 1
QFN-40 5.0V Commercial 10 1
QFN-40 5.0V Commercial 11 1
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Quality & RoHS

Part Number RoHS | Exempt RoHS Halogen Free REACH TSCA MSL Rating / Peak Reflow Package
SP339EER1-L/TR N Y Y Y Y L3 / 260ᵒC QFN40 6x6 OPT1
SP339EER1-L N Y Y Y Y L3 / 260ᵒC QFN40 6x6 OPT1

Click on the links above to download the Certificate of Non-Use of Hazardous Substances.

Additional Quality Documentation may be available, please Contact Support.

Parts & Purchasing

Part Number Pkg Code Min Temp Max Temp Status Suggested Replacement Buy Now Order Samples PDN
SP339ECR1-L QFN40 6x6 OPT1 0 70 OBS SP339EER1-L
SP339ECR1-L/TR QFN40 6x6 OPT1 0 70 OBS SP339ECR1-L
SP339EER1-L QFN40 6x6 OPT1 -40 85 Active Order
SP339EER1-L/TR QFN40 6x6 OPT1 -40 85 Active Order
XR21B1420IL28-0A-EVB 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.


Pkg Code Details Quantities Dimensions PDF
QFN40 6x6 OPT1
  • 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: 490
  • 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: Quadrant 1
  • Dimensions: mm
  • Length: 6.00
  • Width: 6.00
  • Thickness: 1.00
  • Lead Pitch: 0.50


Distribution Date Description File
01/12/2021 Product Discontinuation Notice
12/12/2018 Product Discontinuation Notice
07/11/2017 Product Discontinuation Notification
01/05/2017 Addition of an alternate qualified location, ANST, China.
01/13/2015 Material Change. Qualified copper wire bonding assembly in addition to currently qualified gold wire bonding assembly in Unisem, Ipoh.
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.

FAQs & Support

Search our list of FAQs for answers to common technical questions.
For material content, environmental, quality and reliability questions review the Quality tab or visit our Quality page.
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Submit a Technical Support Question As a New Question

For RS-232 it is 50 feet (15 meters), or the cable length equal to a capacitance of 2500 pF, at a maximum transmission rate of 19.2kbps. When we reduce the baud rate, it allows for longer cable length. For Example:


Baud Rate (bps)

Maximum RS-232 Cable Length (ft)









For RS-485 / RS-422 the data rate can exceed 10Mbps depending on the cable length. A cable length of 15 meters (50 feet) will do a maximum of 10Mbps. A cable length of 1200 meters (4000 feet) will do a maximum of 90kbps over 24 AWG gauge twisted pair cable (with 10 pF/ft). Refer to Annex A TIA/EIA-422-B. Also refer the RS-485 Cable Lengths vs. Data Signaling Rate Application Note (AN-292).

ESD tests are “destructive tests.” The part is tested until it suffers damage. Therefore parts cannot be 100% tested in production, instead a sample of parts are characterized during the product qualification. The test procedure consists of “zapping” pins with a given voltage using the appropriate model and then running the part through electrical tests to check for functionality or performance degradation.

ESD is caused by static electricity. In order for an ESD event to occur there must be a buildup of static charge. Very high charge levels are actually quite rare. In a normal factory environment, taking basic ESD precautions (grounding-straps, anti-static smocks, ionizers, humidity control, etc.) static levels can be kept below a few tens of volts. In an uncontrolled environment, like an office, static levels rarely get above 2000 volts. Under some worstcase conditions (wearing synthetic fabrics, rubbing against synthetic upholstered furniture, extremely low humidity)
levels can go as high as 12 to 15 thousand volts. Actually to get to 15000 volts or higher you would need to be in an uncomfortably dry environment (humidity below 10%) otherwise static charge will naturally dissipate through corona discharge. It would definitely be considered a “bad hair day.” Humans can generally feel a static shock only above 3000 volts. A discharge greater than 4000 volts can cause an audible “pop.” But repeated lower level discharges can be imperceptible and still may have a cumulative damaging effect on sensitive ICs. All ICs, even those with robust protection, can be damaged if they are hit hard enough or often enough.

Most ICs in a typical system are at greatest risk of ESD damage in the factory when the PCB is assembled and the system is being built. After the system is put together they are soldered onto the PCB and shielded within a metal or plastic system enclosure. Interface ICs are designed to attach to an external connector that could be exposed to ESD when a cable is plugged in or when a person or object touches the connector. These interface pins are most likely to see ESD exposure and therefore benefit from additional protection.

Actually the letter “E” could have two different meanings, depending on where it is in the part number. Most of our interface devices are available in different temperature grades. Commercial temperature (0 to 70C) has a “C” after the numeric part number. Industrial-extended temperature (-40 to +85C) use the letter E. So for example SP485CN is commercial and SP485EN is industrial. The second letter indicates the package type, in this case N for narrow-SOIC. Another E in the suffix indicates that this device has enhanced ESD protection, typically of ±15000Volts on the interface pins. Devices that do not have the enhanced ESD still contain built-in ESD protection of at least ±2000Volts. For example the SP485ECN is ESD rated up to ±15kV, and the SP485CN is rated for ±2kV HBM.

Yes, the center pad should be connected to ground with a minimum of 5 vias to the GND plane (one at each corner and one in the middle). It is common to use 9 vias to GND (3 rows of 3 vias inside the pad). This helps thermal dissipation / conduction and electrical requirements for the device.

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How to Design a Multiprotocol System using Only 1 Connector

Industrial networks support multiple serial interfaces such as RS-485 and RS-232.  Using a multiprotocol transceiver enables industrial equipment to support both protocols using only one connector. Enabling both smaller and lower cost equipment designs. This video describes how to design multiprotocol systems using only one connector.