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STMicroelectronics ST485CDR
- Part No.:
- ST485CDR
- Manufacturer:
- STMicroelectronics
- Category:
- Drivers, Receivers, Transceivers
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
ST485CDR.pdf
- Description:
- IC TRANSCEIVER HALF 1/1 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:21,361
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Product details
Overview
ST485CDR from STMicroelectronics is a low-power, half-duplex RS-485/RS-422 transceiver in SO-8 package, featuring 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 for bidirectional multipoint bus communication and is rated for 0 °C to 70 °C operation.
For engineers reviewing the ST485CDR datasheet, ST485CDR pinout, ST485CDR application, or ST485CDR equivalent, key selection criteria include bus drive capability (64-node support), thermal shutdown protection, 5 V single-supply operation, and SO-8 tape-and-reel packaging for automated assembly.
Technical Context
The ST485CDR implements a half-duplex RS-485 transceiver architecture with independent driver enable (DE) and receiver enable (RE) controls, enabling precise bus arbitration. Its driver features short-circuit current limiting and thermal shutdown, forcing outputs into high-impedance state under overload - critical for robust multi-drop networks.
The receiver delivers 70 mV typical hysteresis and operates across –7 V to +12 V common-mode voltage, supporting noise-immune differential signaling over long cables. Propagation delays (30 ns driver, ≤130 ns receiver) and 5 ns output skew ensure timing integrity at up to 2.5 Mbps data rates.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 5 V ±5 % - enables direct integration with standard logic rails without level-shifting. |
| Quiescent Current | 300 µA typ. - reduces standby power in battery-backed or energy-sensitive industrial nodes. |
| Common-Mode Range | –7 V to +12 V - accommodates ground potential differences across extended industrial cabling. |
| Driver Propagation Delay | 30 ns typ. - supports reliable 2.5 Mbps half-duplex communication on 54 Ω differential loads. |
| Receiver Hysteresis | 70 mV typ. - improves noise immunity against EMI-induced false triggering on noisy factory floors. |
| Bus Node Capacity | Up to 64 transceivers - allows scalable daisy-chained topology in building automation or PLC backplanes. |
| Thermal Shutdown | Integrated - disables driver outputs during sustained short-circuit, preventing latch-up or damage. |
Pinout & Package
ST485CDR uses an SO-8 (Small Outline-8) surface-mount package, 5.0 mm × 4.0 mm body, 1.27 mm pitch, tape-and-reel packaging (2500 units/reel), compliant with ECOPACK® environmental standards.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 RO | Receiver output | CMOS-compatible logic-level output reflecting differential A–B state; active only when RE = L. |
| 2 RE | Receiver enable (active-low) | Controls receiver output state; high-impedance when RE = H, enabling bus sharing. |
| 3 DE | Driver enable (active-high) | Activates driver when high; forces A/B into high-Z when low - essential for half-duplex direction control. |
| 4 DI | Driver input | Logic-level input that determines polarity of differential driver output (A/B). |
| 5 GND | Ground reference | Signal return path for internal circuitry and I/O pins; must be connected to system ground plane. |
| 6 A | Non-inverting bus terminal | Transmits/receives positive half of RS-485 differential pair; connects directly to twisted-pair A line. |
| 7 B | Inverting bus terminal | Transmits/receives negative half of RS-485 differential pair; connects directly to twisted-pair B line. |
| 8 VCC | Positive supply | 5 V DC input powering both driver and receiver; bypass capacitor (0.1 µF) required near pin. |
Key Features
| Feature | Design Value |
|---|---|
| Low-power operation | 300 µA supply current enables use in always-on remote sensors without compromising battery life. |
| Robust bus protection | Driver thermal shutdown + current limiting prevents failure during cable shorts or miswiring. |
| Wide common-mode tolerance | –7 V to +12 V input range maintains functionality despite ground offsets in distributed systems. |
| Fast, low-skew timing | 30 ns driver delay and 5 ns skew preserve signal integrity at 2.5 Mbps over 1200 m cables. |
| High-impedance control | Independent DE/RE enables precise tri-state management for collision-free half-duplex arbitration. |
Applications
| Industrial PLC Networks | Building Automation Systems |
|---|---|
|
Use Scenario: Connecting temperature controllers, I/O modules, and HMIs over 500+ meter RS-485 daisy chains in factory environments. IC Role / Device Role / Timing Role: Half-duplex transceiver managing bidirectional Modbus RTU polling between master and slave nodes. Use Value: 64-node bus capacity and –7 V to +12 V common-mode range tolerate ground shifts across large facilities. |
Use Scenario: Interfacing HVAC controllers, lighting panels, and fire alarm nodes via RS-485 backbone in commercial buildings. IC Role / Device Role / Timing Role: Isolated bus node transceiver handling scheduled status reporting and command relay in time-synchronized networks. Use Value: 300 µA quiescent current minimizes standby load on backup power supplies during grid outages. |
| Energy Metering Gateways | Remote Sensor Aggregators |
|
Use Scenario: Collecting consumption data from 32+ smart meters installed across utility distribution cabinets. IC Role / Device Role / Timing Role: RS-485 interface IC converting UART commands to differential bus signals for DLMS/COSEM protocol exchange. Use Value: Thermal shutdown protects gateway hardware during field wiring faults or lightning-induced surges on outdoor runs. |
Use Scenario: Consolidating analog sensor readings (pressure, humidity, vibration) from wireless edge nodes into wired backbone. IC Role / Device Role / Timing Role: Low-power transceiver enabling periodic wake-up and burst transmission in battery-operated aggregators. Use Value: 70 mV receiver hysteresis rejects EMI from nearby motors or switching power supplies in industrial enclosures. |
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 quiescent current (300 µA vs. 230 µA typ.), no thermal shutdown, same SO-8 package. | Lacks driver fault protection; suitable only where short-circuit risk is mitigated externally. | Select when cost sensitivity outweighs need for integrated overload safety. |
| SN65HVD72DR | 3.3 V supply, ±15 kV ESD protection (IEC 61000-4-2), 1/8 unit load (128-node bus), SO-8. | Designed for higher ESD immunity and greater node density in harsher environments. | Select for new designs requiring 3.3 V compatibility or certified ESD resilience in medical or transportation systems. |
Compared with MAX485CPA+ and SN65HVD72DR, the ST485CDR provides optimal balance of thermal protection, 5 V compatibility, and industrial temperature margin - making it preferred for legacy 5 V PLC upgrades and cost-constrained infrastructure deployments.
Availability
ST485CDR is available at Aetrix Electronics and suitable for industrial PLC networks, building automation systems, and energy metering gateways requiring stable component supply, long-term lifecycle support, and SO-8 tape-and-reel delivery for SMT production.
Supply support for ST485CDR 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 interface solutions for industrial, automotive, and consumer markets.
The ST485 series belongs to ST's industrial interface portfolio, engineered specifically for robust, low-power RS-485/RS-422 communication in harsh electrical environments with wide ground potential variation.
FAQ
What is the maximum data rate supported by the ST485CDR?
The ST485CDR supports up to 2.5 Mbps under standard test conditions (RDIF = 54 Ω, CL = 100 pF). This rating assumes proper termination, controlled impedance cabling, and minimal stub length. At lower data rates (e.g., 115.2 kbps), it reliably operates over distances exceeding 1200 meters with standard AWG24 twisted pair.
Does the ST485CDR include fail-safe biasing resistors?
No, the ST485CDR does not integrate fail-safe biasing resistors. External pull-up on A and pull-down on B (e.g., 560 Ω each to VCC/GND) are required to ensure RO = high when the bus is idle or disconnected. This prevents undefined receiver output states during open-circuit or unterminated conditions.
Can the ST485CDR operate with a 3.3 V supply?
No, the ST485CDR is specified only for 5 V ±5 % operation. Its VIH/VIL thresholds (2.0 V/0.8 V) and internal regulator design require 4.75–5.25 V. For 3.3 V systems, consider ST's ST3485 series or TI's SN65HVD7x family, which are explicitly rated for 3.3 V operation.
How does thermal shutdown behave during driver overload?
When driver output current exceeds safe limits (e.g., sustained short-circuit), internal thermal sensing triggers shutdown within milliseconds, forcing A and B into high-impedance state. Recovery occurs automatically once junction temperature falls below threshold (~140 °C), restoring normal operation without external reset.
ST485CDR 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:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
ST485CDR FAQ
1.How can I place an order for ST485CDR through Aetrix?
Please submit a Request for Quotation (RFQ) for ST485CDR 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 ST485CDR reliable?
The price and inventory of ST485CDR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for ST485CDR is usually 5 days.
3.What payment methods are accepted for ST485CDR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for ST485CDR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for ST485CDR?
ST485CDR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your ST485CDR 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 ST485CDR?
For technical support, including ST485CDR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your ST485CDR requirements.
6.How does Aetrix verify that ST485CDR is sourced from the original manufacturer or authorized distributors?
All ST485CDR 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 ST485CDR meets industry standards.
7.What is the process for return or replacement of ST485CDR?
All ST485CDR units undergo pre-shipment inspection (PSI). If there is an issue with ST485CDR, 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 ST485CDR part is unused and in its original packaging.
Return procedure for ST485CDR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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