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STMicroelectronics ST4485EBDR
- Part No.:
- ST4485EBDR
- Manufacturer:
- STMicroelectronics
- Category:
- Drivers, Receivers, Transceivers
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
ST4485EBDR.pdf
- Description:
- IC TRANSCEIVER HALF 1/1 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,880
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Product details
Overview
ST4485EBDR from STMicroelectronics is a half-duplex, 3.3 V powered RS-485/RS-422 transceiver with ±15 kV HBM ESD protection, guaranteed 20 Mbps data rate, -7 to +12 V common-mode input range, and industry-standard 75176 pinout. It integrates one driver and one receiver in an SO-8 package and is used in industrial control networks requiring robust, high-speed differential communication over noisy long-distance buses.
For engineers reviewing the ST4485EBDR datasheet, ST4485EBDR pinout, ST4485EBDR application, or ST4485EBDR equivalent, key selection criteria include shutdown current (≤1 µA), driver output differential voltage (≥1.5 V into 54 Ω), receiver hysteresis (70 mV), thermal shutdown protection, and interoperability with 5 V logic inputs.
Technical Context
The ST4485EBDR implements a half-duplex transceiver architecture where the same A/B bus terminals serve both driver output and receiver input functions. Control logic uses separate DE (driver enable) and RE (receiver enable) pins, allowing independent activation and supporting low-power shutdown when DE = low and RE = high.
Driver output stages feature short-circuit current limiting and thermal shutdown that forces outputs into high-impedance state under overload. Receiver includes fail-safe biasing that guarantees high RO output when A/B lines are floating or unterminated - critical for bus idle-state reliability in multi-drop systems.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply voltage | 3.0–3.6 V: Enables direct compatibility with modern 3.3 V logic domains without level-shifting or charge pumps. |
| Data rate | 20 Mbps guaranteed: Supports high-speed deterministic communication in real-time industrial Ethernet backbones and motion control links. |
| ESD protection | ±15 kV HBM / ±8 kV IEC 1000-4-2 contact: Eliminates need for external TVS diodes in panel-mounted PLC I/O modules. |
| Common-mode range | −7 V to +12 V: Ensures reliable operation across electrically noisy factory floors with ground potential differences up to 19 V. |
| Shutdown current | ≤1 µA max: Allows battery-backed remote sensors to maintain RS-485 connectivity for >10 years on coin-cell power. |
| Bus node count | Up to 64 unit loads: Permits large-scale distributed I/O networks without repeaters in building automation systems. |
| Operating temperature | −40 °C to +105 °C: Qualified for under-hood automotive gateways and outdoor telecom cabinets without derating. |
Pinout & Package
ST4485EBDR is housed in a standard SO-8 (Small Outline, 150 mil width) package with gull-wing leads, RoHS-compliant and ECOPACK® certified. The package measures 4.9 × 3.9 × 1.75 mm and supports tape-and-reel delivery (2500 units/reel).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 RO | Receiver output | CMOS-compatible logic-level output; high when A–B ≥ 200 mV, low when A–B ≤ −200 mV; failsafe-high if A/B floating. |
| 2 RE | Receiver enable | Active-low control: enables RO when low; high-impedance when high; combined with DE low triggers 1 µA shutdown mode. |
| 3 DE | Driver enable | Active-high control: enables A/B driver outputs when high; high-impedance when low; shutdown triggered only when DE = low AND RE = high. |
| 4 DI | Driver input | Logic-level input controlling A/B polarity: DI low → A low / B high; DI high → A high / B low. |
| 5 GND | Ground reference | Signal return for VCC, logic inputs, and receiver common-mode reference; must be star-connected to minimize ground bounce in multi-node buses. |
| 6 A | Non-inverting bus terminal | Shared driver output / receiver input; connects to RS-485 bus A line; requires 120 Ω termination at segment ends. |
| 7 B | Inverting bus terminal | Shared driver output / receiver input; connects to RS-485 bus B line; polarity inverted relative to A for differential signaling. |
| 8 VCC | Power supply | 3.3 V supply input; bypass capacitor (100 nF ceramic) required within 5 mm of pin for noise immunity at 20 Mbps. |
Key Features
| Feature | Design Value |
|---|---|
| Fail-safe receiver | Guaranteed high RO output with floating or unterminated A/B inputs - prevents spurious UART framing errors during bus initialization or fault conditions. |
| Thermal shutdown | Driver automatically enters high-Z state upon sustained overcurrent or elevated junction temperature - protects against latch-up and PCB trace damage during shorted bus events. |
| 5 V logic compatible | DE, RE, and DI accept 0–5 V input levels while powered from 3.3 V - simplifies interface to legacy microcontrollers and FPGA I/O banks without level shifters. |
| Low propagation skew | tPDS ≤ 5 ns and tRPDS ≤ 3 ns ensure matched rising/falling delays across A/B outputs and RO - preserves signal integrity in timing-critical encoder feedback loops. |
Applications
| Industrial PLC Backplane | Smart Energy Metering |
|---|---|
Use Scenario: Modular programmable logic controllers with hot-swappable I/O cards communicating via RS-485 backplane. IC Role / Device Role / Timing Role: Half-duplex transceiver managing point-to-point or multi-drop serial command/response traffic between CPU and analog/digital I/O modules. Use Value: ±15 kV ESD rating withstands repeated card insertion/removal; 20 Mbps supports fast configuration downloads and real-time diagnostics without bus arbitration overhead. | Use Scenario: Two-way AMI (Advanced Metering Infrastructure) communication between utility smart meters and concentrators over twisted-pair distribution lines. IC Role / Device Role / Timing Role: Physical layer transceiver implementing DLMS/COSEM protocol over RS-485 physical medium in ANSI C12.19 and IEC 62056 standards. Use Value: −40 °C to +105 °C rating ensures outdoor meter operation in desert and arctic climates; 64-node support scales to neighborhood-level data aggregation. |
| Factory Floor Motion Control | Building Automation BACnet MS/TP |
Use Scenario: Synchronized servo drive networks using RS-485-based position loop feedback in CNC machines and robotic arms. IC Role / Device Role / Timing Role: High-speed differential transceiver delivering time-stamped encoder data and motion commands with sub-microsecond jitter tolerance. Use Value: 12 ns typical transition time and ≤5 ns propagation skew preserve edge alignment across multi-axis systems; thermal shutdown prevents damage during motor stall faults. | Use Scenario: BACnet Master-Slave/Token-Passing (MS/TP) network connecting HVAC controllers, thermostats, and sensors in commercial buildings. IC Role / Device Role / Timing Role: RS-485 PHY enabling deterministic token rotation and slave polling at 76.8 kbps–1.0 Mbps data rates per ASHRAE Standard 135. Use Value: Fail-safe receiver ensures master retains bus control during cable disconnection; 1 µA shutdown extends battery life in wireless-to-wired gateway bridges. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar RS-485 transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX3485ESA+ | Same SO-8 package, 20 Mbps rated, but only ±12 kV HBM ESD; no IEC 1000-4-2 contact discharge rating specified. | Lacks certified IEC contact discharge protection - unsuitable for field-serviceable equipment exposed to frequent human handling. | Select MAX3485ESA+ only for cost-sensitive internal board-to-board links where HBM-only ESD suffices. |
| SN65HVD72DR | 3.3 V, 20 Mbps, ±16 kV HBM, but features slew-rate control (16–20 Mbps selectable); SO-8 footprint differs (pin 1 location shifted). | Slew-rate select allows noise reduction on long cables but requires layout revision; not drop-in replaceable due to pin-1 offset. | Choose SN65HVD72DR when EMI reduction on >300 m runs is prioritized over mechanical interchangeability. |
Compared with MAX3485ESA+ and SN65HVD72DR, ST4485EBDR uniquely combines full IEC 1000-4-2 contact discharge certification, exact 75176 pinout compliance, and guaranteed fail-safe behavior - making it optimal for industrial field devices requiring zero-integration-risk replacement and regulatory audit readiness.
Availability
ST4485EBDR is available at Aetrix Electronics and suitable for industrial PLC backplanes, smart energy metering infrastructure, factory floor motion control networks, and building automation BACnet MS/TP systems requiring stable component supply across extended product lifecycles.
Supply support for ST4485EBDR 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 microcontrollers, power ICs, sensors, and analog/mixed-signal products for industrial, automotive, and consumer markets.
The ST4485EBDR belongs to ST's RS-485/422 transceiver product line, engineered specifically for rugged, high-speed industrial communications where ESD resilience, thermal robustness, and fail-safe reliability are non-negotiable design requirements.
FAQ
What is the minimum load impedance the ST4485EBDR driver can drive at 20 Mbps?
The ST4485EBDR driver is characterized and guaranteed for 20 Mbps operation into a 54 Ω differential load (standard RS-485 termination), delivering ≥1.5 V differential output voltage. Driving lower impedances - such as 30 Ω - may reduce signal amplitude below specification and increase jitter; ST does not guarantee 20 Mbps performance below 54 Ω.
Does the ST4485EBDR support automatic direction control (Auto RTS)?
No. The ST4485EBDR requires external control of DE and RE pins via MCU GPIO or dedicated direction-control logic. It does not integrate auto-direction circuitry; therefore, systems must implement software- or hardware-managed enable sequencing to avoid bus contention during transmit/receive transitions.
Can ST4485EBDR operate with a 5 V supply?
No. Absolute maximum VCC is 7 V, but functional operation is specified only from 3.0 V to 3.6 V. Applying 5 V risks permanent damage: internal regulator and ESD structures are optimized for 3.3 V rail; exceeding 3.6 V violates electrical characteristics and voids parametric guarantees including ESD rating and data rate.
How does the fail-safe receiver behave when A and B are shorted together?
When A and B are shorted, the differential input voltage is 0 V - within the receiver's undefined region (−200 mV < VID < +200 mV). In this condition, RO output is not guaranteed and may oscillate or settle unpredictably; external bias resistors (e.g., A→VCC, B→GND) are required to force a known fail-safe state in shorted-bus fault scenarios.
ST4485EBDR 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:
- -
- Data Rate:
- 20Mbps
- Voltage - Supply:
- 3V ~ 3.6V
- Operating Temperature:
- -40°C ~ 105°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
ST4485EBDR FAQ
1.How can I place an order for ST4485EBDR through Aetrix?
Please submit a Request for Quotation (RFQ) for ST4485EBDR 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 ST4485EBDR reliable?
The price and inventory of ST4485EBDR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for ST4485EBDR is usually 5 days.
3.What payment methods are accepted for ST4485EBDR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for ST4485EBDR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for ST4485EBDR?
ST4485EBDR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your ST4485EBDR 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 ST4485EBDR?
For technical support, including ST4485EBDR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your ST4485EBDR requirements.
6.How does Aetrix verify that ST4485EBDR is sourced from the original manufacturer or authorized distributors?
All ST4485EBDR 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 ST4485EBDR meets industry standards.
7.What is the process for return or replacement of ST4485EBDR?
All ST4485EBDR units undergo pre-shipment inspection (PSI). If there is an issue with ST4485EBDR, 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 ST4485EBDR part is unused and in its original packaging.
Return procedure for ST4485EBDR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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