SP485 - 5Mbps Low Power Half-Duplex RS-485 Transceiver | MaxLinear
Référence : SP485 ✓ Actif| Qté | Prix unitaire | Total |
|---|---|---|
| 1 | $1.85 | $1,85 |
| 10 | $1.62 | $16,20 |
| 100 | $1.34 | $134,00 |
| 500 | $1.15 | $575,00 |
| 1 000 | $0.97 | $970,00 |
SP485 Présentation
A RS-485 (Recommended Standard 485) transceiver is a physical-layer interface IC that converts the differential voltage of a balanced twisted-pair bus to single-ended logic levels used by UARTs, MCUs, and FPGAs. The SP485 belongs to the broader Interface IC family and specifically implements the TIA/EIA-485-A standard, which allows up to 32 unit loads on a single multi-drop bus and supports cable lengths up to 1200 m at lower data rates. By integrating both the differential driver and differential receiver in a single IC, the SP485 reduces BOM cost and PCB footprint versus discrete implementations.
Key features include 5 Mbps signalling rate, 1/8 unit-load support allowing up to 256 nodes on the bus, thermal shutdown protection, short-circuit protection on the driver outputs, and a wide common-mode range of −7 V to +12 V. The receiver features fail-safe biasing to guarantee a logic-high output when the bus is open, shorted, or idle, eliminating the need for external fail-safe resistors. The half-duplex architecture shares a single differential pair for transmit and receive, controlled by the DE (driver enable) and RE (receiver enable) pins.
The BiCMOS architecture combines bipolar drive transistors for robust bus output swings with CMOS logic for low quiescent current. This dual-process approach allows the SP485 to deliver ±60 mA of driver output current for driving heavily loaded buses while drawing only a few hundred microamps of supply current. The internal charge pump generates the rail-to-rail driver output swing needed to meet RS-485 voltage requirements across the wide common-mode range.
Typical applications include industrial field-bus networks such as Modbus RTU and PROFIBUS, building automation networks, point-of-sale terminals, multi-drop HVAC control, and long-cable RS-485 links between PLCs and remote I/O. The SP485 is also widely used in Arduino, ESP32, and Raspberry Pi Modbus shields that require 5 V signalling.
When designing with the SP485, place 120 Ω termination resistors at both ends of the bus and use twisted-pair cable with 100 Ω characteristic impedance. Enable the driver only when actively transmitting to prevent bus contention, and bias the bus with a fail-safe resistor network if your application cannot tolerate the propagation delay through the internal biasing.
This page synthesizes drop-in pin-compatible equivalents (MAX485, ST485, LTC485, ADM485, ISL3179), verified distributor pricing tiers, and application-specific design notes that go beyond the manufacturer datasheet.
Alternatives de remplacement direct pour SP485 — même boîtier, compatible broche à broche. Les références à boîtier différent nécessitant une retouche du PCB sont exclues.
Outil de comparaison rapide — sélectionnez des références alternatives pour une comparaison côte à côte :
SP485EEN-L/TR
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
SP483CN
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
SP481EN
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
MAX485ESA
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
ST485ECDR
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
LTC485CN8
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
ADM485EARZ
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
SP485 Spécifications
| Protocol | RS-485, RS-422 |
| Fonction | Transceiver |
| Number of Drivers/Receivers | 1/1 |
| Duplex | Half-Duplex |
| Débit de données | 5 Mbps |
| Tension d'alimentation | 5 V |
| Common-Mode Range | −7 V to +12 V |
| Driver Output Current | ±60 mA |
| ESD Protection (HBM, Bus Pins) | ±15 kV |
| Boîtier | 8-Pin SOIC (NSOIC) |
| Type de montage | Surface Mount |
| Statut RoHS | Compliant |
| Lead-Free | Yes |
Configuration des broches de SP485
| Broche 1 | RO — Receiver Output (logic-level, referenced to VCC) |
| Broche 2 | RE — Receiver Enable (active-low, internal pull-down) |
| Broche 3 | DE — Driver Enable (active-high, internal pull-down) |
| Broche 4 | DI — Driver Input (logic-level, referenced to VCC) |
| Broche 5 | GND — Ground |
| Broche 6 | A — Non-inverting differential bus line |
| Broche 7 | B — Inverting differential bus line |
| Broche 8 | VCC — +5 V supply input |
Applications typiques
SP485 convient pour 6 applications: Industrial Modbus RTU Field-Bus, Building Automation Networks (BACnet, Lighting Control), Point-of-Sale Terminal Daisy-Chain, Arduino / ESP32 Modbus Shields, Long-Cable PLC to Remote I/O Links, Solar Inverter Monitoring Bus.
Industrial Modbus RTU Field-Bus
The SP485 is widely used as the physical-layer transceiver on Modbus RTU field-bus segments running at 9600–115200 baud over shielded twisted pair. Its ±15 kV HBM ESD on bus pins survives the harsh electrical environment of factory floors, while the ±60 mA driver output easily drives 32-unit-load buses up to 1200 m. Fail-safe receiver biasing guarantees a logic-high RO output when the bus is idle, which prevents false UART start bits. Paired with an STM32F4 or ESP32 UART, the SP485 forms the lowest-cost 5 V Modbus node in PLC racks, remote I/O modules, and motor drives.
Recommandé
Building Automation Networks (BACnet, Lighting Control)
HVAC and lighting control panels use the SP485 to communicate over BACnet MS-TP or proprietary RS-485 lighting protocols at 76.8 kbps over building-wide cable trays. The half-duplex topology with shared A/B differential pair matches the SP485's pin-strapping perfectly: a single GPIO toggles DE and RE-bar to switch between transmit and receive. The −7 V to +12 V common-mode range tolerates ground-potential differences between floors fed by separate transformers. Up to 256 nodes are addressable thanks to the SP485's 1/8 unit load, far exceeding the RS-485 minimum of 32.
Recommandé
Point-of-Sale Terminal Daisy-Chain
Multi-lane POS systems use the SP485 to daisy-chain cash drawers, customer displays, and receipt printers over a single 4-wire RS-485 backbone. Each terminal uses the SP485's 1/8 unit load to coexist with up to 31 other terminals on the bus, simplifying cabling versus USB hubs. The 5 V supply matches common POS MCU rails, eliminating the need for level shifters. Hotenda's cross-reference lists the MAX485 as a drop-in alternative for sourcing flexibility.
Recommandé
Arduino / ESP32 Modbus Shields
The popular 'MAX485 module' ecosystem used with Arduino Uno, ESP32, and Raspberry Pi Pico is electrically compatible with the SP485 in the SOIC-8 footprint. At 5 V supply, the SP485's DI/RO pins wire directly to the microcontroller's UART TX/RX with no level translation. Its 5 Mbps ceiling exceeds the 115.2 kbps typical Modbus baud, providing 40× margin for protocol overhead and retries. Makers can swap the module's MAX485 chip with the pin-compatible SP485 for higher baud rates without PCB changes.
Recommandé
Long-Cable PLC to Remote I/O Links
PLC racks communicate with remote I/O blocks over multi-hundred-metre RS-485 cables where the SP485's ±60 mA driver output overcomes cable attenuation. Used with 120 Ω termination at both ends and twisted-pair cable of 100 Ω characteristic impedance, the link runs reliably at 115.2 kbps over 1200 m per the RS-485 standard. The device's wide common-mode range tolerates ground-potential rise between distant racks. Hotenda's cross-reference notes the ST485 as a common pin-compatible second-source for STMicro-preferred designs.
Recommandé
Solar Inverter Monitoring Bus
String inverters in commercial solar arrays use the SP485 on the inter-inverter RS-485 bus to report telemetry to a data logger. The −40 °C to +85 °C industrial temperature range tolerated by the SP485 family makes it suitable for outdoor combiner boxes. Up to 32 inverters share a single twisted pair, reducing installation cost versus Ethernet. The half-duplex topology is ideal because inverters only transmit during scheduled telemetry windows, allowing the bus to idle most of the time. Cross-brand ADM485 is commonly listed as a pin-compatible alternative for higher-ESD installations.
Recommandé
Récapitulatif des produits recommandés
Données de référence d'ingénierie pour SP485 — comparaison, recommandations de conception et informations de conformité.
Guide de sélection
Comparaison avec les alternatives
| Paramètre | Ce produit | SP485EEN-L/TR | SP483CN | MAX485ESA | ST485ECDR | LTC485CN8 | ADM485EARZ |
|---|---|---|---|---|---|---|---|
| Brand | MaxLinear | MaxLinear | MaxLinear | Analog Devices | STMicroelectronics | Analog Devices | Analog Devices |
| Package | SOIC-8 | SOIC-8 - same | SOIC-8 - same | SOIC-8 - same | SOIC-8 - same | SOIC-8 - same | SOIC-8 - same |
| Data Rate | 5 Mbps | 5 Mbps | ≤250 kbps (slew-rate limited) | 2.5 Mbps | 2.5 Mbps | 2.5 Mbps | 2.5 Mbps |
| Supply Voltage | 5 V | 5 V | 5 V | 5 V | 5 V | 5 V | 5 V |
| Duplex | Half-Duplex | Half-Duplex | Half-Duplex | Half-Duplex | Half-Duplex | Half-Duplex | Half-Duplex |
| Shutdown Mode | No | No | Yes | No | No | No | No |
| Approx. Unit Price | $1.85 | $1.95 | $1.90 | $2.20 | $1.60 | $3.10 | $2.85 |
Principaux différenciateurs
- 5 Mbps data rate versus 2.5 Mbps industry standard (vs MAX485ESA)
- 1/8 unit load supports 256 nodes versus 32 for legacy parts (vs ST485ECDR)
- Integrated fail-safe biasing eliminates external resistors (vs LTC485CN8)
Notes de conception
Always tie RE (pin 2) low and DE (pin 3) high to enable the driver when actively transmitting; leaving both floating can result in bus contention or high-impedance states. Only one device on the bus should drive at a time. The receiver is enabled when RE is low, so a typical firmware sequence asserts DE only during transmit windows and keeps RE low for continuous receive monitoring. Failing to manage DE/RE timing is the most common SP485 design error.
Place 120 Ω termination resistors at the physical ends of the bus, not at every node - multiple terminators load the bus and reduce signal amplitude. Keep the A/B traces matched in length and routed as a differential pair with 100 Ω characteristic impedance, using a ground reference plane underneath. Place 100 nF decoupling caps close to VCC (pin 8) and add a 10 µF bulk capacitor on the supply rail. Twisted-pair cable with overall shield is recommended for industrial installations; tie the shield to ground at one end only to avoid ground loops.
Because the SP485 is NOT slew-rate limited, reflections on long cables can cause EMI issues above 250 kbps. Estimated: at 5 Mbps, a 10 m cable with 5 ns/m propagation delay yields ~50 ns round-trip reflection, comparable to the bit period of 200 ns - so 120 Ω termination is mandatory. For runs below 250 kbps or EMI-sensitive environments, the SP483 (slew-rate-limited) variant is recommended instead. Use a scope on A/B to verify clean edges during prototype bring-up.
The SP485 draws roughly 500 µA quiescent current when both driver and receiver are enabled, and up to a few mA during active transmission into a 60 Ω load. Estimated: at 5 V supply and 60 mA driver current, peak power dissipation is ~300 mW per device. For dense multi-node designs, calculate total bus current and ensure the 5 V regulator can supply worst-case load. The thermal shutdown circuit protects against output short circuits, but persistent faults should be investigated by the host firmware.
Unterminated stubs longer than 1/10 of the bit-cell rise time act as antennas and corrupt bus signals - keep stubs shorter than ~10 cm at 5 Mbps. For EMI-sensitive installations, add common-mode chokes on the A/B lines near the connector and use a shielded cable with the shield bonded to chassis ground at one end. The SP485's internal fail-safe biasing eliminates the need for external pull-up/pull-down resistors on the bus, which simplifies the BOM but does not replace proper termination.
Informations de conformité
RoHS and lead-free confirmed per MaxLinear product page; AEC-Q100 not qualified for this base part (automotive variants exist in MaxLinear's portfolio but the SP485 itself is industrial-grade).
