Overview
Information | RS-485 Transceiver with Extended IEC ESD and EFT Protection |
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Supported Protocols | RS-485, RS-422 |
Supply Voltage (Nom) (V) | 3.3, 5 |
No. of Tx | 1 |
No. of Rx | 1 |
Duplex | Half |
Data Rate (MAX) (Mbps) | 0.25 |
EFT (±kV) | 2 |
HBM ESD (kV) | 15 |
IEC 61000-4-2 Contact (±kV) | 12 |
Rx Fail-Safe | Advanced |
Multi-Drop Nodes | 256 |
Transient Tolerance (V) | - |
Fault Tolerance (V) | -15 to 15 |
VL Pin | - |
Temperature Range (°C) | -40 to 125 |
Package | NSOIC-8 |
ICC (Max) (mA) | 1.5 |
Shutdown | ✔ |
Typ Shutdown Current (µA) | 0.1 |
Hot Swap | ✔ |
PROFIBUS (5V) or High Output (3V) | ✔ |
The MxL83121 and MxL83122 (MxL8312x family) of half-duplex RS-485 transceivers support up to 500kbps communication in harsh industrial environments. The bus pins tolerate high levels of IEC electrical fast transients (EFT), IEC electrostatic discharge (ESD), and provide an extended common mode range.
Two product options with slew controlled 250kbps and 500kbps speeds are specifically designed to excel at long-distance communication. The combination of integrated EFT and ESD protection, wide common mode, and low slew rate provide a high degree of protection, immunity to noise, and ultra-low EMI.
High receiver input impedance allows 256 transceivers to share a common data bus while maintaining signal margin and without excessive loading or use of expensive repeaters. Enhanced failsafe circuitry ensures receivers provide the expected output when the bus is shorted or left open under both terminated and unterminated conditions. Drivers include built-in short-circuit protection and a thermal-overload shutdown to protect against excessive power dissipation from bus contention.
- Meets or exceeds the requirements of the TIA/EIA-485A standard
- Low slew-rate drivers for reliable long-distance communication
- Differential output exceeds 2.1V for PROFIBUS compatibility with a 5V supply
- Wide supply range from 3.0 to 5.5V
- Extended operating temperature range from –40°C to 125°C
- Extended operational common-mode range of ±12V
- Low-power shutdown mode
- Enhanced failsafe protection for open, short, idle
- Glitch-free power-up/down hot plug capability
- 1/8 unit load (256 bus nodes)
- Drop-in compatible NSOIC package
- Robust system protection
- ±2kV EFT (IEC 61000-4-4)
- ±12kV ESD Contact (IEC 61000-4-2)
- ±15kV ESD Human Body Model
- Motor drives
- HVAC systems
- Industrial and single-board computers
- Smart Grid
- Building security and automation
- Industrial and process control equipment
- Industrial transport
Documentation & Design Tools
Type | Title | Version | Date | File Size |
---|---|---|---|---|
Data Sheets | RS-485/422 Transceivers with Extended IEC ESD and EFT Protection | R00 | August 2024 | 1.1 MB |
Application Notes | Signaling Common Mode Voltage Operating Range Application Note | R00 | March 2025 | 2.3 MB |
Application Notes | RS-485 Transceivers in Fieldbus Networks | R00 | October 2024 | 2.4 MB |
Application Notes | Electric Fast Transient (EFT) Application Note | R00 | September 2024 | 2.5 MB |
Product Flyers | MxL83121, MxL83122 Half-Duplex RS-485 Flyer | R02 | November 2024 | 960.7 KB |
Product Brochures | Interface Brochure | R02 | November 2024 | 3.6 MB |
Quality & RoHS
Parts & Purchasing
Part Number | Pkg Code | Min Temp | Max Temp | Status | Buy Now | Order Samples |
---|---|---|---|---|---|---|
MXL83121E-ADA-R | NSOIC8 | -40 | 125 | Active | Order |
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.
Packaging
Pkg Code | Details | Quantities | Dimensions |
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NSOIC8 |
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FAQs & Support
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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) |
19200 | 50 |
9600 | 500 |
4800 | 1000 |
2400 | 3000 |
Fail Safe is an attempt to keep the output of the RS-485 receiver to a known state. Transceivers may have standard fail safe or advanced / enhanced receiver fail safe features. Standard fail safe supports open inputs while enhanced fail safe transceivers such as the SP339 and XR34350 support open input, shorted input and undriven terminated lines without external biasing. See Application Note ANI-22 for more detail.
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.
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Yes, this is possible using one RS-485 transceiver. The microcontrollers will have to be addressable and have tri-state outputs. The RS-485 device can be controlled by the host via the DE/RE pin. The micros will have to be in either receiving mode or tri-state mode when the RS-485 transceiver is transmitting data. When the host transmits it will have to send an address to the specific micro. If any micro transmits the transceiver will have to be in receiving mode and all other micros will have to be in receive or tri-state. So the host would have to initiate this sequence by addressing the micro first then switch the transceiver to receive.
The half duplex system would have a bus with one transceiver and multiple microcontrollers all tied to the bus. For 5V systems the SP485 family can be used. For 3V systems the SP3070 family can be used. The require speed will determine the part number. The SP3078 part runs up to speeds of 16Mbps. See the parametric search on https://www.exar.com/products/interface/serial-transceivers/rs485-422 for more options.
Care must be taken to assure the transceiver can drive the multiple micros in RX mode.
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.