SP485R - 1/10 Unit Load RS-485 Transceiver | MaxLinear
MPN: SP485R ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.95 | $0.95 |
| 10 | $0.85 | $8.50 |
| 100 | $0.72 | $72.00 |
| 500 | $0.62 | $310.00 |
| 1,000 | $0.54 | $540.00 |
| 3,000 | $0.46 | $1,380.00 |
SP485R Overview
An RS-485 transceiver is a physical-layer interface IC that converts between a UART's TTL/CMOS logic levels and the differential voltage signaling required by the TIA/EIA-485 standard. The standard defines a half-duplex, multipoint differential bus capable of driving cables up to 1200 m at speeds up to 10 Mbps, with common-mode voltage tolerance up to 12 V and robust noise immunity. The 1/10 unit-load rating of the SP485R is a TIA/EIA-485 bus-loading metric meaning each receiver presents only 1/10 of one standard unit load, allowing roughly 10x more devices on the bus than the legacy 32-node limit. Transceivers such as the SP485R form a critical layer in the protocol stack, sitting between the UART/MAC and the physical copper medium in industrial fieldbus, Modbus RTU, PROFIBUS, and DMX512 systems.
The SP485R's headline features are a 1/10 unit load (RIN approximately 150 kOhm typical), 5 Mbps data rate, half-duplex driver/receiver with tri-state control, 5 V single-supply operation, and an integrated shutdown pin for low-power idle states. Differential driver outputs swing the EIA-485-required 1.5 V minimum across a 54 Ohm load while maintaining reduced EMI through controlled slew rates.
The architecture is a classic bipolar differential line driver and receiver pair with on-chip bandgap reference and thermal protection. The receiver's input hysteresis and high input impedance (at least 120 kOhm per datasheet) reduce bus loading and preserve signal integrity at high node counts. Thermal shutdown protects the output stage against bus faults such as shorts to ground or supply.
Typical applications include industrial multi-drop networks, building automation, HVAC controls, security camera RS-485 links, utility metering, DMX512 lighting, and any design that must exceed the standard 32-node RS-485 limit without resorting to repeaters. The wide common-mode range (typically -7 V to +12 V) supports real-world installations with ground-potential differences.
When designing with the SP485R, ensure proper termination (120 Ohm at both ends of the bus for long runs), biasing resistors if the bus is idle, and adequate decoupling (0.1 uF ceramic close to VCC). Be aware that the 1/10 unit load figure means up to 400 nodes are allowed only if all transceivers are also 1/10 unit-load rated - mixing standard and 1/10 unit-load parts breaks the math.
This page synthesizes real distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet alone.
Drop-in alternatives for SP485R — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with SP485R (same form factor and footprint) — differing in Data Rate, Mounting Type, Package, Protocol, Supply Voltage.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
SP485REN
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
SP485REP-L
✅ Drop-In📋 Reference alternative (not in catalog)
SP485RCP-L
✅ Drop-In📋 Reference alternative (not in catalog)
MAX485ESA
✅ Drop-In📋 Reference alternative (not in catalog)
ADM485ARZ-REEL
✅ Drop-In✓ In Stock
$1.62 / Unit
View Datasheet →SN65HVD485EDR
✅ Drop-In📋 Reference alternative (not in catalog)
ISL8485EIBZ
✅ Drop-In📋 Reference alternative (not in catalog)
SP485R Specifications
| Function | Transceiver |
| Protocol | RS-485 |
| Number of Drivers/Receivers | 1/1 |
| Duplex | Half |
| Data Rate | 5 Mbps |
| Supply Voltage | 4.75 V to 5.25 V |
| Receiver Input Impedance (RIN) | 120 kOhm minimum, 150 kOhm typical (1/10 unit load) |
| Bus Loading | 1/10 unit load (supports 400+ transceivers on bus) |
| Input Sensitivity | +/-200 mV |
| Common-Mode Input Voltage Range | -7 V to +12 V |
| Shutdown Mode | Yes |
| Package | 8-pin narrow SOIC (SOIC-8) or 8-pin PDIP |
| Mounting Type | Surface Mount (SOIC) / Through-Hole (PDIP) |
| Pin-to-Pin Equivalent | SP485 (with higher RIN) |
SP485R Pin Configuration
| Pin 1 | RO — Receiver output |
| Pin 2 | RE — Receiver enable (active low) |
| Pin 3 | DE — Driver enable (active high) |
| Pin 4 | DI — Driver input |
| Pin 5 | GND — Ground |
| Pin 6 | A — Non-inverting driver output / non-inverting receiver input |
| Pin 7 | B — Inverting driver output / inverting receiver input |
| Pin 8 | VCC — 5 V supply |
Typical Applications
SP485R is suitable for 7 applications: Industrial Multi-Drop Fieldbus Networks, Building Automation and HVAC Control, Security Camera and Access Control Networks, Utility Metering and AMI Backhaul, DMX512 Lighting and Stage Control, Solar Inverter and Battery Management Comms, Point-of-Sale and Kiosk Peripherals.
Industrial Multi-Drop Fieldbus Networks
The SP485R's 1/10 unit-load receiver input (RIN approximately 150 kOhm typical) and -7 V to +12 V common-mode tolerance make it well suited for industrial multi-drop fieldbus backbones that exceed the standard 32-node RS-485 limit. With this part, designs can connect over 400 nodes such as PLC I/O modules, motor drives, and remote sensors on a single twisted pair without active repeaters, simplifying wiring harnesses and reducing installation cost. The 5 Mbps data rate covers Modbus RTU, PROFIBUS-DP, and similar protocols used in factory automation. Termination uses 120 Ohm at both ends of the trunk with biasing resistors to keep the bus in a defined idle state. Estimated: at full 400-node fan-out the cumulative bus capacitance must stay under 50 pF per node to preserve rise-time margin.
Recommended
Building Automation and HVAC Control
In building automation, the SP485R drives RS-485 buses linking BACnet MS/TP or Modbus controllers, VAV damper actuators, and rooftop-unit controllers across hundreds of feet of unshielded twisted pair. The wide -7 V to +12 V common-mode input range absorbs ground-potential differences between floors or wings of a large building, while the 1/10 unit-load input allows dense sensor and actuator fan-outs without repeaters. The integrated shutdown pin lets a controller put the transceiver in a sub-100 uA sleep state between scheduled polls, useful for battery-backed controllers or energy-harvesting wireless bridges that wake briefly to exchange telemetry. Per the MaxLinear datasheet, the part is specified for 5 V single-supply operation; design accordingly.
Recommended
Security Camera and Access Control Networks
Surveillance networks use the SP485R to drive PTZ telemetry, access-control readers, and intercom panels over RS-485 daisy-chains. The half-duplex direction control lets a single twisted pair carry both telemetry command frames and status responses from each device. The 5 Mbps capability supports 1080p PTZ telemetry at 30 fps alongside concurrent telemetry channels, while the wide common-mode tolerance rejects ground noise injected by long cable runs alongside AC mains. A shutdown pin allows the camera head to fully power-down the bus transceiver during sleep mode, drawing negligible idle current per the MaxLinear datasheet. Terminate the bus with 120 Ohm at each end and bias the lines to keep the receiver output defined when no driver is active.
Recommended
Utility Metering and AMI Backhaul
Advanced Metering Infrastructure (AMI) concentrators aggregate data from electric, water, and gas meters over long RS-485 runs. The SP485R's high receiver input impedance (at least 120 kOhm) is essential for concentrators that poll hundreds of meters per segment, avoiding repeater hardware. The wide common-mode voltage range tolerates ground potential differences across utility service areas, and the part's industrial-grade robustness supports outdoor cabinet environments. Per the datasheet, drive the bus at 5 Mbps for short AMI trunks or step down to 115.2 kbps or 9600 baud for long rural runs to maximize distance. Estimated: at 9600 baud cable lengths to 1200 m remain reliable given proper 120 Ohm termination and 22 AWG twisted pair.
Recommended
DMX512 Lighting and Stage Control
DMX512 theatrical and architectural lighting networks are rooted in EIA-485 electricals, making the SP485R a natural fit for fixture nodes and dimmer racks. The 250 kbps DMX512 data rate sits comfortably within the SP485R's 5 Mbps envelope, while its -7 V to +12 V common-mode tolerance handles the long cable bundles and ground-potential differences typical of large venues. The 1/10 unit-load rating supports dense daisy-chains of dimmers and moving lights on a single universe. The shutdown pin is rarely used in DMX (always-on bus), but the low standby current still benefits battery-powered lighting test fixtures. Per MaxLinear datasheet, terminating the DMX link with 120 Ohm at the last fixture is mandatory per the DMX512 standard.
Recommended
Solar Inverter and Battery Management Comms
Solar inverter monitoring networks and battery management systems use RS-485 to daisy-chain inverter telemetry, battery module state-of-charge, and string-monitoring combiner boxes. The SP485R's high-impedance receiver input allows 400+ battery modules on a single BMS bus, important for grid-scale storage where each rack may contain dozens of battery modules. The shutdown pin is useful for solar micro-inverters that must power down their comm bus when AC mains are off to meet standby losses; per the datasheet, the shutdown pin current draw is sub-1 uA typical. The wide common-mode tolerance handles long DC-bus-coupled cable runs where ground potentials shift under load. Estimated: select 120 Ohm termination only at the two physical ends of the bus, leaving intermediate drops un-terminated to prevent reflections.
Recommended
Point-of-Sale and Kiosk Peripherals
Retail point-of-sale terminals and self-service kiosks daisy-chain receipt printers, barcode scanners, customer displays, and cash-drawer triggers over RS-485 in some installations. The SP485R supports a clean 5 V logic interface to the host MCU and 5 Mbps data rate to handle aggregated peripheral traffic. The shutdown pin is useful for energy-star compliant kiosk idle modes where the comm bus can be put to sleep when the kiosk is unattended. The 8-pin SOIC package fits into space-constrained kiosk mainboards. Per the MaxLinear datasheet, ensure 0.1 uF ceramic decoupling close to the VCC pin and place 120 Ohm termination at the two physical ends of the daisy chain only. Estimated: total drop length should stay under 30 m at 5 Mbps to avoid signal-integrity issues.
Recommended
Recommended Products Summary
Engineering reference data for SP485R — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | SP485REN | SP485REP-L | MAX485ESA | ADM485ARZ | SN65HVD485EDR | ISL8485EIBZ |
|---|---|---|---|---|---|---|---|
| Brand | MaxLinear | MaxLinear | MaxLinear | Analog Devices | Analog Devices | Texas Instruments | Renesas Electronics |
| Package | SOIC-8 | SOIC-8 - same | PDIP-8 - through-hole variant | SOIC-8 - same | SOIC-8 - same | SOIC-8 - same | SOIC-8 - same |
| Bus Loading (Unit Load) | 1/10 unit load | 1/10 unit load | 1/10 unit load | 1/1 unit load | 1/1 unit load | 1/2 unit load | 1/8 unit load |
| Max Nodes on Bus | 400+ | 400+ | 400+ | 32 | 32 | 64 | 256 |
| Data Rate | 5 Mbps | 5 Mbps | 5 Mbps | 2.5 Mbps | 5 Mbps | 5 Mbps | 5 Mbps |
| 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 | 4.75 V to 5.25 V | 4.75 V to 5.25 V |
| Common-Mode Range | -7 V to +12 V | -7 V to +12 V | -7 V to +12 V | -7 V to +12 V | -7 V to +12 V | -7 V to +12 V | -7 V to +12 V |
| Shutdown Pin | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
Key Differentiators
- 1/10 unit-load receiver supports 400+ nodes (vs MAX485ESA)
- Wide common-mode tolerance with proven fieldbus robustness (vs ADM485ARZ)
- Pin-to-pin compatible with the SP485 for upgrade flexibility (vs SP485 (non-R))
- 5 Mbps data rate covers Modbus RTU, PROFIBUS-DP, and DMX512 (vs SN65HVD485EDR)
Design Notes
Do not assume that any standard RS-485 transceiver can replace the SP485R in a high-node-count bus. The 1/10 unit-load rating (RIN approximately 150 kOhm typical) is what enables 400+ nodes - mixing in a 1/1 unit-load part such as the MAX485 silently breaks the bus-loading math and causes communication failures under heavy node fan-out. Always re-validate node count whenever you cross-reference transceivers, and check the unit-load spec on the alternative's datasheet rather than relying on package and pinout alone.
Place a 0.1 uF ceramic decoupling capacitor as close as physically possible to the SP485R VCC pin (pin 8), with a short, wide ground return to the GND pin (pin 5). For boards with long VCC traces, add a bulk 10 uF tantalum or ceramic cap near the transceiver. Keep the A and B differential traces matched in length (within 5 mm) and route them as a 100-ohm differential pair, ideally over a continuous ground plane. Avoid routing the bus near switching regulator inductors or other noisy traces to preserve the +/-200 mV receiver input sensitivity per the MaxLinear datasheet.
Terminate the RS-485 bus with 120 Ohm resistors at both physical ends only - never in the middle, or reflections will degrade signal integrity. For high-node-count SP485R buses exceeding 32 nodes, biasing resistors (typically 680 Ohm fail-safe pull-up on A and 680 Ohm pull-down on B to a defined logic level) are mandatory to keep the receiver output in a known state when all drivers are tri-stated. The SP485R's high input impedance tolerates these biasing networks without significant DC loading, but verify bias resistor values against actual node count and cable capacitance.
The SP485R includes on-chip thermal shutdown that protects the output stage during bus fault events such as shorts to ground or supply. At 5 V VCC with a fully loaded 54 Ohm bus and a sustained short, the driver dissipation can exceed 1 W - thermal shutdown will engage and the part will retry once cooled. Ensure the PCB copper area under the SOIC-8 thermal pad (or DIP-8 pins) provides at least 100 mm^2 of 1 oz copper pour to keep junction temperature within safe limits during fault events per the datasheet thermal resistance figures.
Compliance Information
Compliance status not stated explicitly in verified web data. SP485R is an industrial-grade IC, not AEC-Q100 qualified for automotive. MaxLinear product page lists active lifecycle status as of 2026-10-11.
