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STMicroelectronics ST485BN
- Part No.:
- ST485BN
- Manufacturer:
- STMicroelectronics
- Category:
- Drivers, Receivers, Transceivers
- Package:
- 8-DIP (0.300", 7.62mm)
- Datasheet:
-
ST485BN.pdf
- Description:
- IC TRANSCEIVER HALF 1/1 8DIP
- Quantity:
- Payment:
- Shipping:
Inventory:2,770
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Product details
Overview
ST485BN from STMicroelectronics is a low-power, half-duplex RS-485/RS-422 transceiver in DIP-8 package, operating from a single 5 V supply with 300 µA typical quiescent current, -40 °C to +85 °C industrial temperature range, and 70 mV input hysteresis for noise immunity in noisy industrial bus environments.
For engineers reviewing the ST485BN datasheet, ST485BN pinout, ST485BN application, or ST485BN equivalent, key selection considerations include common-mode voltage range (-7 V to +12 V), driver thermal shutdown protection, 30 ns propagation delay, and compatibility with multi-drop RS-485 networks supporting up to 64 nodes.
Technical Context
The ST485BN integrates one driver and one receiver in a single IC, designed specifically for half-duplex bidirectional communication on multipoint transmission lines. Its driver features short-circuit current limiting and thermal shutdown, forcing outputs into high-impedance state under overload - critical for bus fault resilience.
Receiver operation includes 70 mV typical hysteresis and supports wide common-mode input range (-7 V to +12 V), enabling robust data reception across electrically noisy industrial installations. Logic control uses separate RE (receiver enable) and DE (driver enable) pins for precise direction management without bus contention.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 5 V ±5 % - enables direct integration with standard logic rails and eliminates need for auxiliary regulators. |
| Quiescent Current | 300 µA typ. - reduces system-level power budget in battery-backed or energy-constrained remote nodes. |
| Common-Mode Range | -7 V to +12 V - tolerates ground potential differences across long cable runs in factory automation systems. |
| Propagation Delay | 30 ns typ. - supports reliable 2.5 Mbps data rates at distances up to 100 m over twisted-pair cabling. |
| Input Hysteresis | 70 mV typ. - suppresses false triggering from EMI-induced signal ringing on RS-485 differential lines. |
| Driver Output Protection | Current limiting + thermal shutdown - prevents latch-up or permanent damage during bus short-circuits or miswiring. |
| Bus Node Capacity | Up to 64 transceivers - allows scalable deployment in distributed PLC I/O networks without repeaters. |
Pinout & Package
DIP-8 package with through-hole mounting, 2.54 mm lead pitch, 9.8 mm × 8.8 mm body size, and 3.3 mm height - compatible with legacy industrial PCB layouts and wave-soldering processes.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 RO | Receiver output | CMOS-compatible logic-level output reflecting differential A–B state; sinks/sours ±4 mA. |
| 2 RE | Receiver enable (active-low) | Asserting low enables RO; high places RO in high-impedance - essential for bus arbitration in multi-node systems. |
| 3 DE | Driver enable (active-high) | Asserting high enables driver outputs A/B; low forces A/B into high-Z - prevents bus conflicts during direction switching. |
| 4 DI | Driver input | CMOS-level input accepting 0.8 V / 2.0 V thresholds; directly driven by microcontroller GPIO. |
| 5 GND | Ground reference | Signal return path for both driver and receiver circuits; must be connected to local system ground plane. |
| 6 A | Non-inverting bus terminal | Transmits/receives positive half of differential pair; connects to RS-485 bus A line. |
| 7 B | Inverting bus terminal | Transmits/receives negative half of differential pair; connects to RS-485 bus B line. |
| 8 VCC | Positive supply | 5 V power input; requires local 100 nF ceramic decoupling capacitor placed within 5 mm of pin. |
Key Features
| Feature | Design Value |
|---|---|
| Low-power operation | 300 µA supply current enables use in always-on industrial sensors with minimal thermal impact. |
| Thermal shutdown protection | Driver automatically enters high-Z state during sustained overload - preserves device integrity without external circuitry. |
| Wide common-mode range | -7 V to +12 V input tolerance accommodates ground shifts in multi-chassis factory networks. |
| Controlled enable timing | 70 ns output enable/disable delays ensure clean direction transitions without glitches on shared bus lines. |
| High noise immunity | 70 mV input hysteresis rejects transient coupling from motor drives or relay switching in industrial cabinets. |
Applications
| Programmable Logic Controller (PLC) I/O Modules | Industrial Motor Drive Communication |
|---|---|
Use Scenario: Connecting distributed I/O expansion modules to main PLC CPU via daisy-chained RS-485 bus in harsh factory environments. IC Role / Device Role / Timing Role: Half-duplex transceiver managing bidirectional command/status exchange between controller and remote digital/analog I/O units. Use Value: -40 °C to +85 °C rating ensures reliability in unconditioned control cabinets; 64-node capacity supports large-scale modular architectures. | Use Scenario: Enabling real-time parameter readback and fault reporting from variable-frequency drives (VFDs) to central SCADA systems. IC Role / Device Role / Timing Role: RS-485 physical layer interface translating UART signals to robust differential bus signaling over 200+ meter cable runs. Use Value: 30 ns propagation delay maintains timing margin at 2.5 Mbps baud rate; thermal shutdown protects against drive bus faults. |
| Building Automation System (BAS) Controllers | Remote Terminal Unit (RTU) Telemetry |
Use Scenario: Interfacing HVAC controllers, lighting panels, and fire alarm nodes over shared RS-485 backbone in commercial buildings. IC Role / Device Role / Timing Role: Bus transceiver implementing Modbus RTU protocol at physical layer with configurable node addressing. Use Value: 70 mV hysteresis prevents spurious command execution due to EMI from elevator motors or fluorescent ballasts. | Use Scenario: Supporting telemetry data transmission from geographically dispersed utility meters and environmental sensors to central monitoring stations. IC Role / Device Role / Timing Role: Low-quiescent-current transceiver enabling solar-powered RTUs to maintain 24/7 bus readiness with minimal battery drain. Use Value: 300 µA supply current extends battery life in off-grid deployments; DIP-8 package simplifies field-replaceable module design. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar RS-485 transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX485ESA+ | Same DIP-8 package and 5 V operation, but higher quiescent current (300 µA vs. 230 µA typ.) and narrower common-mode range (-7 V to +12 V same, but lower noise immunity at extremes). | Valid for Modbus RTU in commercial BAS, but less suited for high-EMI motor drive cabinets where ST485BN's hysteresis provides superior margin. | Select MAX485ESA+ only when legacy MAXIM footprint compatibility is required and thermal stress is minimal. |
| SN65HVD72DR | SO-8 only, 3.3 V supply, integrated fail-safe biasing, and ±16 kV ESD protection - no DIP-8 option or 5 V support. | Designed for modern 3.3 V microcontrollers and high-ESD environments (e.g., outdoor kiosks), not drop-in replacement for ST485BN's industrial 5 V DIP layout. | Choose SN65HVD72DR for new 3.3 V designs requiring enhanced ESD robustness; not suitable for retrofitting existing ST485BN-based boards. |
Compared with MAX485ESA+ and SN65HVD72DR, the ST485BN uniquely balances industrial temperature range, DIP-8 through-hole compatibility, 5 V operation, and proven thermal fault resilience - making it optimal for legacy and new-build industrial control hardware where board-level serviceability and bus survivability are prioritized.
Availability
ST485BN is available at Aetrix Electronics and suitable for programmable logic controller (PLC) I/O modules, industrial motor drive communication, and building automation system (BAS) controllers requiring stable component supply across extended product lifecycles.
Supply support for ST485BN 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, delivering silicon solutions for automotive, industrial, and power management applications since 1987.
The ST485 series belongs to ST's industrial interface portfolio, engineered specifically for robust, low-power RS-485/RS-422 communication in factory automation, energy infrastructure, and process control systems.
FAQ
What is the maximum data rate supported by the ST485BN?
The ST485BN supports up to 2.5 Mbps under standard test conditions (RDIF = 54 Ω, CL = 100 pF). This rate is achievable over 100 m of twisted-pair cable with proper termination and noise control. Performance degrades at longer distances or higher EMI levels due to signal integrity limits, not internal timing constraints.
Does the ST485BN require external biasing resistors on the RS-485 bus?
No, the ST485BN does not integrate fail-safe biasing. External pull-up on A and pull-down on B (e.g., 560 Ω each to VCC/GND) are required to ensure known idle-state logic level when no driver is active. This prevents receiver output oscillation during bus idle periods in multi-node networks.
Can the ST485BN operate with a 3.3 V supply?
No - the ST485BN is specified only for 5 V ±5 % operation. Supply voltage below 4.75 V violates absolute maximum ratings and causes undefined behavior in driver output swing and receiver threshold accuracy. For 3.3 V systems, consider ST's ST3485 series or TI's SN65HVD7x family.
How does the thermal shutdown feature behave during a bus short-circuit?
When driver output current exceeds safe limits (e.g., A–B shorted), internal thermal sensing triggers shutdown within milliseconds, forcing A and B into high-impedance state. The driver remains disabled until junction temperature falls below the hysteresis threshold (~15 °C below trip point), after which normal operation resumes automatically without reset.
ST485BN 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:
- 2.5Mbps
- Voltage - Supply:
- 4.75V ~ 5.25V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 8-DIP
ST485BN FAQ
1.How can I place an order for ST485BN through Aetrix?
Please submit a Request for Quotation (RFQ) for ST485BN 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 ST485BN reliable?
The price and inventory of ST485BN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for ST485BN is usually 5 days.
3.What payment methods are accepted for ST485BN?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for ST485BN transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for ST485BN?
ST485BN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your ST485BN 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 ST485BN?
For technical support, including ST485BN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your ST485BN requirements.
6.How does Aetrix verify that ST485BN is sourced from the original manufacturer or authorized distributors?
All ST485BN 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 ST485BN meets industry standards.
7.What is the process for return or replacement of ST485BN?
All ST485BN units undergo pre-shipment inspection (PSI). If there is an issue with ST485BN, 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 ST485BN part is unused and in its original packaging.
Return procedure for ST485BN:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
ST485BN Tags
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ATA6561-GAQW-N
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ATA6561-GBQW-N
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