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STMicroelectronics ST485BDR
- Part No.:
- ST485BDR
- Manufacturer:
- STMicroelectronics
- Category:
- Drivers, Receivers, Transceivers
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
ST485BDR.pdf
- Description:
- IC TRANSCEIVER HALF 1/1 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:21,137
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Product details
Overview
ST485BDR from STMicroelectronics is a half-duplex RS-485/RS-422 transceiver with 300 µA quiescent current, ±7 V to +12 V common-mode input range, and 30 ns driver propagation delay. It integrates one driver and one receiver in an SO-8 package, operating from a single 5 V supply, and is designed for industrial bus communication systems requiring low-power, robust multipoint data transmission.
For engineers reviewing the ST485BDR datasheet, ST485BDR pinout, ST485BDR application, or ST485BDR equivalent, key selection criteria include its thermal shutdown protection, 70 mV input hysteresis for noise immunity, 2.5 Mbps maximum data rate, and compatibility with legacy RS-485 infrastructure under extended temperature conditions.
Technical Context
The ST485BDR implements a true half-duplex transceiver architecture with independent driver output enable (DE) and receiver output enable (RE) controls, enabling precise bus arbitration. Its driver features short-circuit current limiting and thermal shutdown that forces outputs into high-impedance state during overload-critical for fault-tolerant bus operation.
The receiver provides 24 kΩ input resistance and operates across –7 V to +12 V common-mode voltage, supporting long-line noise rejection. Input hysteresis of 70 mV (typ.) ensures stable logic transitions in electrically noisy industrial environments without external Schmitt triggers.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 5 V ±5 % - fixed single-supply operation eliminates need for dual-rail or level-shifting circuitry |
| Quiescent Current | 300 µA (typ.) - enables battery-backed or energy-constrained remote nodes without compromising bus drive capability |
| Common-Mode Range | –7 V to +12 V - supports >1 km cable runs with ground potential differences in factory automation networks |
| Propagation Delay | 30 ns (driver), 130 ns (receiver) - allows reliable 2.5 Mbps full-rate operation on 54 Ω differential lines |
| Differential Output | 1.5 V min (RL = 27 Ω) - meets RS-485 standard minimum VOD for interoperability with legacy transceivers |
| Input Hysteresis | 70 mV (typ.) - suppresses false triggering from EMI-induced signal ringing on unterminated stubs |
| ESD Protection | ±2 kV HBM - provides baseline robustness against handling and board-level electrostatic discharge |
Pinout & Package
ST485BDR is housed in a standard SO-8 (Small Outline, 150 mil width) package with gull-wing leads, RoHS-compliant and ECOPACK® certified. Pin pitch is 1.27 mm, body dimensions are 4.9 × 6.0 × 1.75 mm (L × W × H), suitable for automated SMT assembly and IPC Class 2/3 reliability requirements.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 RO | Receiver output | CMOS-compatible logic-level output driving microcontroller UART RX line; high-impedance when RE = high |
| 2 RE | Receiver output enable | Active-low control: pulls RO to high-Z when asserted, enabling bus sharing with multiple receivers |
| 3 DE | Driver output enable | Active-high control: enables A/B differential driver only when asserted; otherwise A/B float high-Z |
| 4 DI | Driver input | TTL/CMOS-compatible input accepting UART TX signal; referenced to VCC/GND, not bus voltages |
| 5 GND | Ground reference | Local digital ground return for internal logic and driver/receiver biasing; must be star-connected to minimize ground bounce |
| 6 A | Non-inverting bus terminal | Half of differential pair: connects to RS-485 bus A line; outputs high during logic 1, sinks current during logic 0 |
| 7 B | Inverting bus terminal | Half of differential pair: connects to RS-485 bus B line; complementary to A; defines polarity per TIA/EIA-485 standard |
| 8 VCC | Power supply | +5 V DC input powering all internal circuitry; requires local 100 nF ceramic decoupling within 5 mm of pin |
Key Features
| Feature | Design Value |
|---|---|
| Thermal shutdown protection | Automatically disables driver outputs and places A/B in high-impedance state during sustained overcurrent, preventing latch-up or permanent damage |
| 3-state driver and receiver control | Independent DE and RE pins allow precise timing control of bus access and listening windows-essential for collision-free half-duplex protocols |
| Wide common-mode input range | –7 V to +12 V tolerance accommodates ground offsets up to ±12 V between nodes, eliminating need for isolated power or signal conditioning |
| Low propagation skew | 5 ns max driver output skew ensures clean differential edge alignment, preserving signal integrity at 2.5 Mbps on mismatched PCB traces |
| High input impedance receiver | 24 kΩ differential input resistance enables connection of up to 64 unit loads on a single RS-485 bus segment without termination degradation |
Applications
| Industrial PLC Networks | Building Automation Systems |
|---|---|
Use Scenario: Multi-node Modbus RTU network connecting programmable logic controllers, I/O modules, and HMIs over twisted-pair cabling in factory floors with high EMI. IC Role / Device Role / Timing Role: Half-duplex RS-485 transceiver providing galvanically isolated physical layer interface between UART peripherals and shared bus infrastructure. Use Value: 300 µA quiescent current reduces heat buildup in densely packed DIN-rail enclosures; thermal shutdown prevents bus lockup during cable short events. | Use Scenario: Distributed HVAC controller network linking thermostats, valve actuators, and energy meters across commercial buildings using daisy-chained RS-485 wiring. IC Role / Device Role / Timing Role: Bus interface IC translating UART commands into differential signals compliant with TIA/EIA-485-A for noise-immune long-distance communication. Use Value: –40 °C to +85 °C operating range ensures reliable winter startup and summer thermal stability; 70 mV hysteresis rejects switching noise from nearby AC motor drives. |
| Smart Meter Data Collection | Remote SCADA Telemetry |
Use Scenario: AMI (Advanced Metering Infrastructure) endpoint aggregating consumption data from electricity/water/gas meters and transmitting via RS-485 to concentrator units. IC Role / Device Role / Timing Role: Low-power transceiver enabling battery-operated or energy-harvested endpoints to maintain bus connectivity with minimal standby current draw. Use Value: 300 µA ICC (no load) extends battery life beyond 10 years in sleep-wake cycles; SO-8 package supports compact PCB layout for meter module integration. | Use Scenario: Oil & gas pipeline monitoring system using solar-powered RTUs to relay pressure, flow, and valve status over 500 m+ RS-485 links to central SCADA. IC Role / Device Role / Timing Role: Robust physical layer device interfacing microcontroller UARTs to harsh outdoor RS-485 field buses subject to lightning-induced surges and ground differentials. Use Value: ±7 V to +12 V common-mode range handles ground potential shifts across geographically dispersed sites; driver short-circuit current limit (35–250 mA) contains fault energy during surge events. |
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+ | Higher quiescent current (300 µA vs. 230 µA typ.), identical SO-8 footprint and pinout, no thermal shutdown | Lacks driver thermal protection; requires external current limiting or fuse for sustained short-circuit scenarios | Select when cost sensitivity outweighs fault-protection requirement and ambient temperature remains <70 °C |
| SN65HVD72DR | Lower ICC (120 µA typ.), integrated IEC 61000-4-2 ESD (±16 kV), but higher VOD (2.5 V min) and wider supply range (3.0–5.5 V) | Supports mixed-voltage systems and harsher ESD environments; incompatible with strict 5 V-only designs due to lower VCC min | Select for new designs needing enhanced ESD robustness and ultra-low power, accepting revalidation of bus timing margins |
Compared with MAX485ESA+ and SN65HVD72DR, ST485BDR uniquely balances industrial temperature support (–40 °C to +85 °C), built-in thermal shutdown, and proven interoperability in legacy Modbus installations-making it optimal for retrofit and long-lifecycle industrial deployments where reliability trumps marginal power savings.
Availability
ST485BDR is available at Aetrix Electronics and suitable for industrial PLC networks, building automation systems, smart meter data collection, and remote SCADA telemetry requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for ST485BDR 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, MCU, power, and sensor solutions for automotive, industrial, and consumer markets.
The ST485 series belongs to ST's industrial interface product line, engineered specifically for robust, low-power RS-485/RS-422 communication in harsh electromagnetic environments with extended temperature operation and integrated fault protection.
FAQ
What is the maximum data rate supported by ST485BDR?
The ST485BDR supports a maximum data rate of 2.5 Mbps under standard test conditions (RDIF = 54 Ω, CL = 100 pF). This rating assumes proper termination, controlled impedance routing, and compliance with RS-485 signal integrity guidelines-including maintaining differential skew ≤5 ns and minimizing stub length to avoid reflections.
Does ST485BDR require external current-limiting resistors on the A/B lines?
No. The ST485BDR integrates driver short-circuit current limiting (35–250 mA peak) and thermal shutdown, eliminating the need for external series resistors. However, external transient voltage suppressors (TVS) are recommended for lightning or EFT protection in outdoor or industrial installations per IEC 61000-4-5 Level 3.
Can ST485BDR operate with a 3.3 V supply?
No. ST485BDR is specified only for 5 V ±5 % operation (4.75–5.25 V). Attempting 3.3 V operation results in undefined behavior: driver output voltage drops below RS-485 minimum VOD, receiver thresholds shift, and thermal shutdown may not activate correctly. For 3.3 V systems, consider ST's ST3485 series instead.
How many ST485BDR transceivers can share the same RS-485 bus?
Up to 64 unit loads can be connected on a single RS-485 bus segment when using ST485BDR, based on its 24 kΩ receiver input resistance (1/64 of the 1/3 unit-load standard). This assumes proper termination at both ends, total bus capacitance ≤5000 pF, and adherence to maximum stub length limits (≤15 m at 2.5 Mbps) to preserve signal integrity.
ST485BDR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- 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:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
ST485BDR FAQ
1.How can I place an order for ST485BDR through Aetrix?
Please submit a Request for Quotation (RFQ) for ST485BDR 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 ST485BDR reliable?
The price and inventory of ST485BDR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for ST485BDR is usually 5 days.
3.What payment methods are accepted for ST485BDR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for ST485BDR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for ST485BDR?
ST485BDR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your ST485BDR 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 ST485BDR?
For technical support, including ST485BDR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your ST485BDR requirements.
6.How does Aetrix verify that ST485BDR is sourced from the original manufacturer or authorized distributors?
All ST485BDR 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 ST485BDR meets industry standards.
7.What is the process for return or replacement of ST485BDR?
All ST485BDR units undergo pre-shipment inspection (PSI). If there is an issue with ST485BDR, 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 ST485BDR part is unused and in its original packaging.
Return procedure for ST485BDR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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