ST485CDR - 2.5Mbps Low-Power RS-485/RS-422 Transceiver SOIC-8 | ST
部品番号: ST485CDR ✓ 生産中| 数量 | 単価 | 小計 |
|---|---|---|
| 1 | $1.85 | $1.85 |
| 10 | $1.55 | $15.50 |
| 100 | $1.18 | $118.00 |
| 500 | $0.96 | $480.00 |
| 1,000 | $0.82 | $820.00 |
| 2,500 | $0.71 | $1,775.00 |
ST485CDR 概要
An RS-485 transceiver is a differential line driver/receiver IC that translates between a single-ended UART/logic signal and the balanced twisted-pair signaling required by the TIA/EIA-485-A and TIA/EIA-422-B standards. RS-485 supports multi-drop (up to 32 transceivers on one bus) and half-/full-duplex topologies over cable runs of 1200 m, while RS-422 supports dedicated point-to-point or multi-drop simplex links. Within the broader signal-chain taxonomy, RS-485 transceivers are a subset of line transceivers -> interface ICs -> wired communication ICs.
Key features include 2.5 Mbps data rate, 300 uA typical supply current, -7V to +12V common-mode range on the bus pins, internal current limiting on driver outputs, and thermal-shutdown protection that disables the driver if junction temperature exceeds safe limits. The receiver input hysteresis of 70 mV (typical) rejects line noise on long cable runs, and the 1/8-unit-load (or higher) input impedance permits multiple devices on a shared bus with minimal loading.
The ST485CDR uses a bipolar CMOS-compatible driver architecture with slew-rate-controlled output transitions, which limits radiated EMI and reduces reflections on unterminated stubs. The chip is built on a BiCMOS process that delivers RS-485 drive strength (driver short-circuit current limited) while keeping quiescent draw at hundreds of microamperes, several orders of magnitude below legacy bipolar-only designs.
Typical applications include industrial fieldbus links (Modbus RTU, PROFIBUS segments), building automation (BACnet MS-TP, DMX-512 lighting), point-of-sale peripherals, and any MCU UART extension over long cables. The low quiescent current also suits battery-backed monitoring nodes where the bus is idle for long periods.
Designers should provide a 100 nF decoupling capacitor within 5 mm of VCC and add a 100 ohm termination resistor at each end of long runs to suppress signal reflections. The DE and RE pins can be tied together for simplex operation, or driven separately for direction-controlled half-duplex buses.
This page synthesizes distributor pricing, drop-in cross-brand alternatives, and PCB layout notes not collected in the manufacturer datasheet alone, giving engineers a faster path from datasheet search to BOM placement.
ドロップイン代替品: ST485CDR — 同一パッケージでピン互換。PCBの作り直しが必要な異なるパッケージの部品は除外されています。
クイック比較ツール — 並列比較する代替部品を選択:
ST485ECDR
✅ ドロップイン📋 参考代替品（カタログ未掲載）
ST485EBDR
✅ ドロップイン📋 参考代替品（カタログ未掲載）
MAX485ESA+
✅ ドロップイン✓ 在庫あり
$0.92 / 個
データシートを見る →SN75176BDR
✅ ドロップイン✓ 在庫あり
$0.1055 / 個
データシートを見る →SN65HVD72DR
✅ ドロップイン📋 参考代替品（カタログ未掲載）
ST485CDR 仕様
| 機能 | Transceiver |
| Protocol | RS-422, RS-485 |
| Number of Drivers/Receivers | 1/1 |
| Duplex | Half |
| データレート | 2.5 Mbps |
| 電源電圧 | 4.75 V to 5.25 V |
| Supply Current (unloaded, drivers disabled) | 300 uA typical |
| Common-Mode Range (bus pins) | -7 V to +12 V |
| Receiver Input Hysteresis | 70 mV typical |
| 動作温度 | 0C to +70C (C grade) |
| パッケージ | SOIC-8 |
| 実装タイプ | Surface Mount |
| Driver Short-Circuit Protection | Yes, current-limited |
| 熱シャットダウン | Yes |
| RoHS ステータス | Compliant |
ST485CDR ピン構成
| ピン 1 | RO — Receiver output (push-pull, referenced to GND) |
| ピン 2 | RE — Receiver enable, active low (tie to GND to enable RO) |
| ピン 3 | DE — Driver enable, active high (tie high or low to disable Y/Z) |
| ピン 4 | DI — Driver input (TTL/CMOS, drives Y/Z differential pair) |
| ピン 5 | GND — Ground |
| ピン 6 | A / Y — Non-inverting driver output / non-inverting receiver input |
| ピン 7 | B / Z — Inverting driver output / inverting receiver input |
| ピン 8 | VCC — +5V supply input (4.75V to 5.25V) |
主な用途
ST485CDR の用途: 6 件s: Industrial Fieldbus Links (Modbus RTU / PROFIBUS), Building Automation Networks (BACnet MS-TP / DMX-512), Point-of-Sale Peripherals, Long-Cable MCU UART Extension, Solar Inverter / Energy Monitoring Networks, Security and Access Control Panels.
Industrial Fieldbus Links (Modbus RTU / PROFIBUS)
The ST485CDR's 2.5 Mbps data rate and -7V to +12V common-mode tolerance make it well suited for industrial fieldbus segments such as Modbus RTU and PROFIBUS DP subsegments. With 300 uA typical quiescent current and thermal-shutdown-protected drivers, the part keeps idle draw low across long cable runs and survives the line faults common in factory environments. Place one ST485CDR at each end-node, terminate the cable at both ends with 100 ohm resistors, and tie DE and RE together for direction-controlled half-duplex operation when the link is always active.
おすすめ
Building Automation Networks (BACnet MS-TP / DMX-512)
BACnet MS-TP and DMX-512 lighting runs both use RS-485 differential signaling over twisted-pair cable runs of several hundred meters inside commercial buildings. The ST485CDR's industrial temperature variant and 1/1 half-duplex topology line up with these protocols, and its low idle draw keeps power-budgeted HVAC controllers and lighting fixtures within thermal limits. Use the ST485CDR as the bus-side transceiver on each node, isolate the bus with a TVS diode array for surge protection, and keep stub lengths to under one-tenth of the signal rise time for clean 2.5 Mbps operation.
おすすめ
Point-of-Sale Peripherals
POS peripherals (barcode scanners, pole displays, receipt printers, cash-drawer triggers) frequently chain over RS-485 multi-drop to keep cabling simple and robust. The ST485CDR's SOIC-8 footprint drops directly into compact POS PCBs and supports the 2.5 Mbps speeds needed by modern scanner handhelds that stream image data plus barcodes. Its 5V supply aligns with the typical POS board rails, and its 300 uA quiescent current keeps standby draw low in always-on register electronics. Place the transceiver near the RJ-45/DB-9 connector, route the differential pair as 100 ohm impedance, and add 100 ohm termination only on the cable end nodes.
おすすめ
Long-Cable MCU UART Extension
When an MCU UART needs to span tens or hundreds of meters - for example across a parking gate, a greenhouse sensor string, or a security-camera control run - the ST485CDR converts the single-ended logic-level UART into balanced RS-485 differential signaling that rejects common-mode noise picked up on long cable runs. The 2.5 Mbps ceiling comfortably exceeds 115200 baud UART links, and the part's low quiescent draw suits battery-backed sensor nodes. Place one ST485CDR at each cable end, share the bus with up to 31 other transceivers, and use 100 ohm termination plus a fail-safe biasing network for robust idle-state behavior.
おすすめ
Solar Inverter / Energy Monitoring Networks
Solar inverters, battery management systems, and utility-grade energy meters commonly daisy-chain over RS-485 to share telemetry with a central gateway. The ST485CDR's wide 4.75V to 5.25V supply lets it share the inverter's 5V aux rail, and its thermal-shutdown-protected outputs survive the elevated ambient temperatures inside an outdoor inverter enclosure. The 2.5 Mbps speed supports high-resolution metering streams while the 300 uA idle draw keeps parasitic loss low in string-monitoring nodes that spend most of the day idle. Add a TVS diode on the bus pins and an isolated RS-485 interface if the inverter has a high-voltage DC bus.
おすすめ
Security and Access Control Panels
Access-control panels, alarm sensors, and intercom stations often daisy-chain over RS-485 multi-drop with 30 to 50 nodes per run, making the standard 32-unit-load ceiling a real concern. The ST485CDR's standard 1/1 unit-load input is fine for these panel counts, and its 2.5 Mbps speed keeps response times fast even when many nodes are polled. The half-duplex topology matches the typical polling protocol where one controller talks to many readers. Place the transceiver near each panel's terminal block, keep the bus cable away from AC mains wiring, and protect the bus pins with an SMBJ-type TVS for surge immunity on outdoor runs.
おすすめ
おすすめ製品の概要
エンジニアリング参考データ: ST485CDR — 比較、設計ガイダンス、コンプライアンス情報。
選定ガイド
代替品との比較
| パラメータ | この製品 | ST485ECDR | ST485EBDR | MAX485ESA+ | SN75176BDR | SN65HVD72DR |
|---|---|---|---|---|---|---|
| Package | SOIC-8 | SOIC-8 - same | SOIC-8 - same | SOIC-8 - same | SOIC-8 - same | SOIC-8 - same |
| Brand | STMicroelectronics | STMicroelectronics | STMicroelectronics | Analog Devices | Texas Instruments | Texas Instruments |
| Data Rate | 2.5 Mbps | 2.5 Mbps | 2.5 Mbps | 2.5 Mbps | 10 Mbps | 250 kbps (low slew-rate variant) |
| Supply Voltage | 4.75 V to 5.25 V | 4.75 V to 5.25 V | 4.75 V to 5.25 V | 4.75 V to 5.25 V | 4.75 V to 5.25 V | 3.0 V to 3.6 V |
| Operating Temperature | 0C to +70C | -40C to +85C | -40C to +85C | -40C to +85C | 0C to +70C | -40C to +85C |
| Common-Mode Range | -7 V to +12 V | -7 V to +12 V | -7 V to +12 V (enhanced ESD) | -7 V to +12 V | -7 V to +12 V | -7 V to +12 V |
| Duplex | Half | Half | Half | Half | Half | Half |
| Thermal Shutdown | Yes | Yes | Yes | Yes | Yes | Yes |
主な差別化要因
- Lower quiescent current than legacy bipolar-only transceivers （vs SN75176BDR)
- Industrial temperature range option in same SO-8 footprint （vs SN75176BDR (0C to +70C))
- Enhanced ESD protection option in same SO-8 footprint （vs ST485CDR (standard ESD))
- Wider supply and shutdown flexibility vs ST-only family （vs ST485CDR (5V only))
設計ノート
Place a 100 nF X7R decoupling capacitor within 5 mm of the ST485CDR VCC pin (pin 8) and a 10 uF bulk capacitor if the part sits far from the regulator. Route the DI/RO logic traces away from the A/Y and B/Z differential pair to avoid coupling noise into the UART. Keep the SOIC-8 ground pin (pin 5) tied to a low-impedance ground plane that doubles as the reference for the bus shield. Estimated: with 100 nF local plus 10 uF bulk, ripple on VCC during driver transitions stays well below 50 mV at the part's 5V rail.
Treat the A/Y and B/Z traces as a 100 ohm differential pair: match their lengths to within 5 mm, keep them on the same layer with no splits in the ground plane beneath, and avoid crossing any high-current or switching signals. Add a 100 ohm termination resistor at each end of the cable (not at every node) and a fail-safe biasing network (typically a pull-up on A and pull-down on B through 560 ohm resistors) to keep RO at a defined logic level when the bus is idle. Estimated: with characteristic cable impedance of 120 ohm and two end terminations of 100 ohm in parallel, the bus match is 60 ohm, which attenuates reflections within two round-trip times for cables shorter than about 30-40 m at 2.5 Mbps.
Do not leave DE floating - either drive it from a GPIO for direction control or tie it hard low (receiver-only) or hard high (driver-only). Forgetting to terminate long runs causes reflected edges that look like data errors at 2.5 Mbps; check the eye on an oscilloscope before declaring the bus stable. Avoid tying the cable shield to logic ground at every node - tie it at one end only (or through a 100 nF/10 MOhm high-impedance network) to prevent ground loops. Finally, do not exceed the -7V to +12V common-mode range; if the cable runs near large motors or VFDs, add an isolator (e.g. ADM2587E) between the transceiver and the bus.
Although RS-485 transceivers do not dissipate large continuous power, driver short-circuit events (cable shorted to VCC or GND) can push junction temperature above 150C quickly. The ST485CDR's internal thermal-shutdown circuitry cuts the driver output if this happens, but you can reduce the failure rate by adding a 4 to 10 ohm PTC or a 100 mA polyfuse on each bus pin to limit fault current. Estimated: at 5V into a hard short the part could draw 250 mA before thermal shutdown kicks in, so a 100 mA polyfuse trips in tens of milliseconds and keeps the IC within safe operating area.
コンプライアンス情報
RoHS and REACH compliant per ST product page (DigiKey listing 686413). Not AEC-Q100 qualified; use AEC-Q100 listed parts (e.g. MAX22530) for automotive applications.
