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DIP-8 / SOP-8 · MAX485
ActiveRS-485 / RS-422 Transceiver
MAX485
Maxim Integrated · DIP-8 / SOP-8 · RS-485 / RS-422 Transceiver
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Overview
The MAX485 is the original 5 V half-duplex RS-485/RS-422 transceiver from Maxim Integrated (now part of Analog Devices) and remains one of the highest-volume interface ICs ever made. It contains a single differential driver and a single differential receiver with separate DE (driver enable, active high) and /RE (receiver enable, active low) control pins, letting an MCU place the node in transmit, receive, or high-impedance states — the fundamental three-state behavior RS-485 multi-drop buses require.
Because the MAX485 has no slew-rate limiting, it supports full data rates up to 2.5 Mbps; if your cable is long and EMI is a concern, the sibling MAX483/MAX1487 trade speed (250 kbps/120 kbps) for slower edges. The driver is protected by both current limiting and thermal shutdown, receiver inputs tolerate -7 V to +12 V (covering miswired and ground-shifted buses), and quiescent current is only 300 µA typical (500 µA max). Supply is a single 4.75 V to 5.25 V; for 3.3 V systems use the pin-compatible MAX3485.
Fail-safe behavior is worth noting for design review: the MAX485 receiver output is not guaranteed high on an open or fully idle bus without bias resistors, so robust installations add fail-safe biasing (680 ohm to 1 k pull-up on A, pull-down on B) at both ends. Counterfeit MAX485 chips are common on broker markets — clones frequently fail the 2.5 Mbps edge rate or the -7 V receiver range. Genuine ADI/Maxim parts have laser-etched marking and consistent bevel on the pin-1 corner. MOQ is typically 1 reel (2,500 pcs SOP-8) or 100 pcs loose from Shenzhen stock.
Key Features
- Half-duplex RS-485/RS-422, up to 2.5 Mbps with no slew limiting
- Separate DE and /RE enables for true three-state multi-drop nodes
- Driver current limiting + thermal shutdown; receiver inputs -7 V to +12 V
- Single 5 V supply, 300 µA typical quiescent current, DIP-8/SOP-8
Typical Applications
- Modbus RTU networks for meters, PLCs and building automation
- DMX512 stage lighting and architectural LED control
- Long-haul serial links in industrial and telecom equipment
- Arduino/ESP32 RS-485 shields and sensor bus boards
- Multipoint data acquisition over twisted pair up to 1200 m
Specifications
- Function
- Half-Duplex RS-485 / RS-422 Transceiver
- Drivers / Receivers
- 1 / 1
- Max Data Rate
- 2.5 Mbps
- Supply Voltage
- 4.75 to 5.25 V
- Quiescent Current (Max)
- 500 µA
- Receiver Input Range
- -7 to +12 V
- Driver Protection
- Current Limiting + Thermal Shutdown
- Operating Temperature
- 0 to 70 °C
- Pins
- 8
- RoHS
- Compliant
Procurement Tips
Standardize on one package (SOP-8) across all your RS-485 boards so a single reel covers the whole product line, and stock fail-safe bias resistor kits (680 Ω / 120 Ω) alongside — they are the most-omitted components on MAX485 designs.
Frequently Asked Questions
What is the difference between MAX485 and MAX3485?
Function and pinout are identical; the MAX3485 is the 3.3 V version (3.0-3.6 V supply) with 10 Mbps-class performance in newer datasheets, while the MAX485 runs at 5 V up to 2.5 Mbps. Use MAX3485 with 3.3 V MCUs to avoid level translation.
MAX485 vs MAX483/MAX1487 — which do I pick?
All are pin-compatible 8-pin half-duplex transceivers. MAX485: 2.5 Mbps, fastest. MAX483: 250 kbps with slew-limited edges for lower EMI. MAX1487: 120 kbps, supports 1/8 unit load (up to 256 nodes). Pick MAX485 for speed, MAX1487 for large node counts, MAX483 for a middle ground on long cables.
How many nodes can hang on one MAX485 bus?
The MAX485 receiver presents one standard unit load, so up to 32 transceivers share one segment per the RS-485 specification. For 128 or 256 nodes, use fractional-load devices such as the MAX1487 (1/8 UL) or MAX3088.
Do I need termination and bias resistors?
Yes for reliable operation. Place a 120 ohm termination resistor across A/B at each physical end of the bus (matching the cable characteristic impedance), and add fail-safe biasing so the receiver sees a defined idle level — otherwise the MAX485 output can chatter on an unterminated, undriven bus.
Why does my MAX485 board work at 9600 baud but fail at higher rates?
Long stubs and missing termination reflect edges at high speed. Keep stub lengths under 30 cm, terminate both ends, use shielded twisted pair, and verify DE/RE turnaround timing — releasing DE too early truncates the last stop bit, which shows up only at higher baud rates.
How can I tell a genuine MAX485 from a counterfeit?
Genuine ADI/Maxim parts show crisp laser-etched top marking with a beveled pin-1 chamfer, matte-tin leads, and pass full 2.5 Mbps loop timing at 5 V. Clones commonly fail above 500 kbps or clamp incorrectly at -7 V inputs. We electrically test samples from every broker lot.
What is the MOQ and lead time?
MOQ 1 reel (2,500 pcs SOP-8) or 100 pcs loose for prototypes; DIP-8 available by tube. Shenzhen stock ships in 1-2 business days, ADI authorized channel replenishment takes 6-10 weeks.
Alternatives & Equivalents
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