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STMicroelectronics ST485XN
- Part No.:
- ST485XN
- Manufacturer:
- STMicroelectronics
- Category:
- Drivers, Receivers, Transceivers
- Package:
- 8-DIP (0.300", 7.62mm)
- Datasheet:
-
ST485XN.pdf
- Description:
- IC TRANSCEIVER HALF 1/1 8DIP
- Quantity:
- Payment:
- Shipping:
Inventory:3,927
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Product details
Overview
ST485XN from STMicroelectronics is a low-power, half-duplex RS-485/RS-422 transceiver with one driver and one receiver, operating from a single 5 V supply, featuring 300 µA quiescent current, ±7 V to +12 V common-mode input range, and 30 ns propagation delay. It supports up to 64 nodes on a multipoint bus in industrial automation data links.
For engineers reviewing the ST485XN datasheet, ST485XN pinout, ST485XN application, or ST485XN equivalent, key selection criteria include bus node count scalability, thermal shutdown protection under driver overload, 70 mV input hysteresis for noise immunity, and compatibility with legacy DIP-8 and SO-8 PCB footprints.
Technical Context
The ST485XN implements a true half-duplex RS-485 transceiver architecture with independent enable controls: RE (receiver enable) and DE (driver enable) allow precise timing coordination between receive and transmit states. Its driver features short-circuit current limiting and thermal shutdown that forces outputs into high-impedance upon fault detection.
Receiver operation includes wide common-mode voltage tolerance (–7 V to +12 V), 24 kΩ input resistance, and differential threshold switching at ±0.2 V with 70 mV hysteresis - enabling robust operation in electrically noisy factory-floor environments with ground potential differences.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 5 V ±5% - enables direct integration with standard logic rails without LDO overhead |
| Quiescent Current | 300 µA typ. - reduces standby power in battery-backed or energy-constrained remote I/O modules |
| Common-Mode Range | –7 V to +12 V - accommodates ground shifts across long cable runs in distributed control systems |
| Propagation Delay | 30 ns typ. - supports reliable 2.5 Mbps data rates over 1200 m RS-485 lines per EIA/TIA-485 |
| Differential Threshold | ±0.2 V with 70 mV hysteresis - rejects EFT bursts and conducted noise below 70 mV amplitude |
| Driver Output Short-Circuit Protection | 35–250 mA peak current limit with thermal shutdown - prevents latch-up during cable faults or miswiring |
| Input Resistance | 24 kΩ - allows ≥64 unit loads on shared bus per RS-485 standard |
Pinout & Package
ST485XN is available in DIP-8 and SO-8 packages. The DIP-8 variant provides through-hole mounting for prototyping and ruggedized industrial PCBs; SO-8 supports surface-mount reflow assembly for high-density automation controllers.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 RO | Receiver output | CMOS-compatible logic-level output driving MCU UART RX line |
| 2 RE | Receiver enable (active low) | Asserting low enables RO; high places RO in high-impedance - isolates bus during transmit |
| 3 DE | Driver enable (active high) | Asserting high enables A/B differential driver; low disables driver and forces high-Z state |
| 4 DI | Driver input | TTL/CMOS-compatible logic input accepting MCU UART TX signal |
| 5 GND | Ground reference | Signal return path for internal circuitry and biasing of A/B differential pair |
| 6 A | Non-inverting bus terminal | Drives positive half of RS-485 differential signal; receives non-inverted bus voltage |
| 7 B | Inverting bus terminal | Drives negative half of RS-485 differential signal; receives inverted bus voltage |
| 8 VCC | Positive supply | 5 V power rail connection; internal regulation not required |
Key Features
| Feature | Design Value |
|---|---|
| Thermal shutdown protection | Automatically disables driver outputs during sustained overload, preventing permanent damage in field wiring faults |
| 3-state receiver output | RO enters high-impedance when RE = high, enabling multi-drop receiver arbitration without external mux |
| High-impedance driver on power-off | Driver outputs float to high-Z when VCC = 0 V - avoids back-driving powered bus segments during hot-swap |
| Wide temperature range support | Industrial grade (–40 °C to +85 °C) operation validated - suitable for uncontrolled cabinet environments |
| RS-422 compatibility | Configurable for point-to-point RS-422 via 50 Ω load termination - extends use to legacy serial instrumentation links |
Applications
| PLC Remote I/O Module | Building Automation Controller |
|---|---|
Use Scenario: Distributed sensor/actuator nodes communicate over 500 m twisted-pair cabling to central PLC rack. IC Role / Device Role / Timing Role: Half-duplex RS-485 transceiver managing bidirectional Modbus RTU polling cycles at 19.2 kbps. Use Value: 24 kΩ input resistance and ±7 V common-mode range tolerate ground differentials across HVAC zones and elevator shafts. | Use Scenario: BACnet MS/TP network interconnecting chillers, AHUs, and VAV boxes in commercial high-rises. IC Role / Device Role / Timing Role: Physical layer transceiver implementing deterministic token-passing timing with <30 ns skew. Use Value: Thermal shutdown prevents failure during intermittent short circuits caused by conduit damage during retrofit installations. |
| Industrial HMI Terminal | Energy Meter Data Concentrator |
Use Scenario: Touchscreen HMI polls multiple motor drives and safety relays via daisy-chained RS-485. IC Role / Device Role / Timing Role: Bus interface IC handling full-duplex-to-half-duplex protocol translation for legacy drive communication. Use Value: 70 mV input hysteresis suppresses EFT-induced false triggers during contactor switching events near control panels. | Use Scenario: AMI gateway collects consumption data from 32 smart meters over 1 km RS-485 trunk line. IC Role / Device Role / Timing Role: Multi-node transceiver supporting addressable polling with automatic fail-safe biasing. Use Value: 300 µA quiescent current enables >10-year battery life in solar-powered concentrators deployed off-grid. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar RS-485 transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX485CPA+ | Higher ICC (350 µA typ.), no thermal shutdown, same pinout and DC specs | Lacks fault protection in harsh electrical environments | Select when cost sensitivity outweighs need for driver fault resilience |
| SN65HVD72DR | 3.3 V supply only, integrated IEC 61000-4-2 ESD protection (±16 kV), SO-8 only | Requires level-shifting for 5 V MCU interfaces; adds surge immunity | Select for new 3.3 V designs requiring certified ESD robustness in medical or test equipment |
Compared with MAX485CPA+ and SN65HVD72DR, ST485XN uniquely balances 5 V compatibility, thermal fault protection, and industrial temperature rating - making it optimal for retrofitting legacy 5 V control systems where wiring integrity cannot be guaranteed.
Availability
ST485XN is available at Aetrix Electronics and suitable for industrial automation, building management systems, and energy metering applications requiring stable component supply across extended product lifecycles.
Supply support for ST485XN includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing analog, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.
The ST485XN belongs to ST's legacy RS-485 transceiver portfolio, engineered specifically for reliability in electrically noisy, ground-varying industrial networks - emphasizing fault tolerance, bus node density, and long-term parametric stability.
FAQ
What is the maximum recommended bus length for ST485XN at 2.5 Mbps?
The ST485XN supports up to 1200 m at 100 kbps per RS-485 standard; at its rated 2.5 Mbps maximum data rate, the practical bus length is limited to approximately 15 m due to signal integrity constraints from capacitance and skew. Longer runs require reducing data rate or adding repeaters.
Does ST485XN require external termination resistors?
Yes - ST485XN requires a 120 Ω termination resistor placed across the A and B bus lines at both ends of the RS-485 trunk to prevent reflections and ensure signal integrity. The device itself does not integrate termination; external placement is mandatory for reliable high-speed operation.
Can ST485XN operate with a 3.3 V supply?
No - ST485XN is specified only for 5 V ±5% operation. Its VIH/VIL thresholds (2.0 V/0.8 V) and internal biasing assume 5 V logic levels; using 3.3 V risks unreliable control input recognition and degraded driver output swing, violating datasheet operating conditions.
How does the thermal shutdown feature behave during continuous short-circuit events?
Under sustained short-circuit, the driver's thermal shutdown activates within milliseconds, forcing A and B outputs into high-impedance. Once the die cools below the hysteresis threshold (~15 °C below trip point), the driver automatically recovers - enabling self-resetting fault recovery without system reset.
ST485XN Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- 8-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Type:
- Transceiver
- Protocol:
- RS422, RS485
- Number of Drivers/Receivers:
- 1/1
- Duplex:
- Half
- Receiver Hysteresis:
- 70 mV
- Data Rate:
- 5Mbps
- Voltage - Supply:
- 4.75V ~ 5.25V
- Operating Temperature:
- -55°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 8-DIP
ST485XN FAQ
1.How can I place an order for ST485XN through Aetrix?
Please submit a Request for Quotation (RFQ) for ST485XN on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for ST485XN reliable?
The price and inventory of ST485XN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for ST485XN is usually 5 days.
3.What payment methods are accepted for ST485XN?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for ST485XN transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for ST485XN?
ST485XN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your ST485XN order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for ST485XN?
For technical support, including ST485XN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your ST485XN requirements.
6.How does Aetrix verify that ST485XN is sourced from the original manufacturer or authorized distributors?
All ST485XN products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that ST485XN meets industry standards.
7.What is the process for return or replacement of ST485XN?
All ST485XN units undergo pre-shipment inspection (PSI). If there is an issue with ST485XN, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The ST485XN part is unused and in its original packaging.
Return procedure for ST485XN:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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