Programmable RS232/RS485 Transceiver
Data Sheet


The SP331 is a programmable RS-232 and/or RS-485 transceiver IC. The SP331 contains four drivers and four receivers when selected in RS-232 mode; and two drivers and two receivers when selected in RS-485 mode. The SP331 also contains a dual mode which has two RS-232 drivers/receivers plus one differential RS-485 driver/receiver.

The RS-232 transceivers can typically operate at 230kbps while adhering to the RS-232 specifications. The RS-485 transceivers can operate up to 10Mbps while adhering to the RS-485 specifications. The SP331 includes a self-test loopback mode where the driver outputs are internally configured to the receiver inputs. This allows for easy diagnostic serial port testing without using an external loopback plug. The RS-232 and RS-485 drivers can be disabled (High-Z output) by controlling a set of four select pins.

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


  • +5V Only Operation
  • Software Programmable RS-232 or RS-485 Selection
  • Four RS-232 Transceivers iRS-232 Mode
  • Two RS-485 Full-Duplex Transceivers in RS-485 Mode
  • Two RS-232 Transceivers and One RS-485 Transceiver in Dual Mode
  • Self-Testing Loopback Mode
  • Full Driver Tri-State (Hi-Z) Control
  • Ideal for RS-232 to RS-485 conversion


Design Tools


Pkg Code Details Quantities Dimensions PDF
  • JEDEC Reference: MS-013
  • MSL Pb-Free: L3 @ 260ºC
  • MSL SnPb Eutectic: n/a
  • ThetaJA: 58.6ºC/W
  • Bulk Pack Style: Tube
  • Quantity per Bulk Pack: 27
  • Quantity per Reel: 1500
  • Quantity per Tube: 27
  • Quantity per Tray: n/a
  • Reel Size (Dia. x Width x Pitch): 330 x 24 x 12
  • Tape & Reel Unit Orientation: Quadrant 1
  • Dimensions: mm
  • Length: 17.90
  • Width: 7.50
  • Thickness: 2.65
  • Lead Pitch: 1.27

Parts & Purchasing

Part Number Pkg Code RoHS Min Temp Max Temp Status Buy Now Order Samples
SP331CT WSOIC28 0 70 OBS
SP331CT-L WSOIC28 0 70 Active Order
SP331CT-L/TR WSOIC28 0 70 Active Order
SP331ET WSOIC28 -40 85 OBS
SP331ET/TR WSOIC28 -40 85 OBS
SP331ET-L WSOIC28 -40 85 Active Order
SP331ET-L/TR WSOIC28 -40 85 Active Order
Show obsolete parts
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.

Quality Documents

Additional Quality Documentation may be available, please contact customersupport@maxlinear.com.
Distribution Date Description File
02/11/2016 Foundry line qualification, Addition of qualified 6 inch wafer processing line in Silan PCN 15-0727-03 Silan 6 inch-1033.pdf
11/16/2015 Updated information subsequent to original published PCN 15-0625-02 on 09/29/2015. Addendum: Update to package marking. PCN 15-0625-02A UPDATE-1033.pdf
09/29/2015 Greatek as alternate assembly site Addition of an alternate production site, Greatek, Taiwan for 16L, 24L and 28L SOICW PCN 15-0625-02 16L-24L-28L SOICW Greatek-1033.pdf
07/02/2013 Qualified copper wire bonding assembly in addition to currently qualified gold wire bonding assembly in Carsem. Material change. PCN_12-1129-01-1033.pdf
07/30/2010 Process Change. Capacity enhancement. PCN_10-0715-01-1033.pdf
02/22/2010 Process Change Process optimization and clarify conditions for the datasheets parameters. PCN_10-0201-03-1033.pdf
02/28/2007 Product Obsolescence Letter and Discontinuation Notification. Discontinued. POL_022807-1033.pdf
06/26/2006 Amendment of PCN transferring certain Power Management and Interface Products from Hillview fabrication and facility to wafer foundary Episil instead of Silan. See attached Product List Power Management and Interface products as listed are being transfer to external wafer foundry, due to cessation of operations of the sipex Hillview Fabrication manufacturing site PCN 06-0130-16a-1033.pdf
02/02/2006 Announcing transfer of certain Power Management and Interface Products from Hillview fabrication and facility to wafer foundary Silan. See attached Product List Power Management and Interface products as listed are being transfer to external wafer foundry, due to cessation of operations of the sipex Hillview Fabrication manufacturing site PCN-06-0130-16-1033.pdf

Frequently Asked Questions

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.

Yes, the SP331, SP332 and SP334 exceed ±2kV ESD HBM on all pins.  Some interface products have enhanced versions that exceed ±15kV, which applies to the bus data lines.  The parametric search contains ESD information and it is a selection field https://www.exar.com/products/interface/serial-transceivers/multiprotocol/dual-protocol .

The SP331 configured for RS485 mode operate as standard RS485 drivers and 1-Unit Load receivers. The drivers can therefore support up to 32 unit loads coexisting on a shared multidrop RS485 bus. If the other nodes on the bus are less than 1-UL a piece then more nodes can be supported. If a biasing supply or other loads are added to the bus then total number of nodes would be decreased.

The Modes are described on page 8 and Page 11 of the datasheet. Using decimal equivalent; modes 12, 13, 14, can be used for RS485 in either full or half duplex.
Referring to the function table on page 8, modes 12 and 13 are used for half duplex. T1 turns on and off for transmit and receive modes. These same bus lines can be used for the full duplex mode as the transmitter but the receiver is hard wired in a loop back configuration so R3 has to be used as the full-duplex receiver.
If preferred, T3 and R3 can be used as a separate full duplex channel but this requires two more bus lines.

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.

The best way to determine this is to go to exar.com and type the part into the search function. At or near the top of the results you should see something that looks like

In this example, we looked for XRA1201. When you hover over it, it will turn grey and you can click anywhere in the grey box. This brings you to the product page. For example:


Click on Parts & Purchasing, highlighted in yellow above. The screen changes to:


Notice the status column and the “Show obsolete parts” link:


A legend tells you the definition of the different statuses. Click on the “Show obsolete parts” link to see EOL or OBS part numbers along with the Active part numbers:


Another method to find out if a part is OBS or EOL is to click on SUPPORT:


And then Product Change Notifications


Type the part into the search, and click on one of the part numbers from the drop down menu. Then you can look for the Product Discontinuation Notice, which generally is at the top of the list, for example:


If you see this, it tells you that this particular orderable part has been discontinued and when the last order date is, or was. If you click on the file, then you can view the notice we sent about this if you purchased the part in the recent past. It may also advise of a replacement part. When an orderable part first becomes discontinued, Product Discontinuation Notices are sent are sent to those who have purchased the parts in the recent past, if purchased directly, with a dated opportunity to place a last order.