ADM3491AN - 3.3V 20Mbps RS-485 Transceiver | Analog Devices
N.º de pieza: ADM3491AN ✓ ActivoADM3491AN Descripción general
An RS-485 transceiver is an interface integrated circuit that converts logic-level signals into balanced differential signals for reliable communication over longer cables and electrically noisy environments. The differential signaling method improves noise immunity by comparing the two conductors rather than relying on a single-ended voltage. The ADM3491AN belongs to the RS-485 transceiver category, where it combines a transmitter, receiver, and bus-driver circuitry in one low-power device for industrial and embedded data links.
Low power consumption is central to the ADM3491AN design. Its 840 µA operating supply current suits battery-powered and power-sensitive instruments, while the shutdown mode reduces supply current to 2 nA. A 20 Mbps maximum data rate supports high-speed point-to-point or multipoint links, and the receiver input impedance of 19 kΩ permits up to 50 transceivers on a bus. Interoperability with 5 V logic allows the device to connect to controllers operating above its nominal 3.3 V supply level.
The ADM3491 family provides a combination of low-power operation, common-mode range, and transient robustness. Analog Devices specifies operation with a 3.3 V supply across a ±0.3 V tolerance. Its electrical characteristics are specified over the full device temperature range, and the integrated thermal shutdown mechanism provides protection when the output driver is subjected to fault conditions. An 8 ns transmitter skew specification helps preserve timing relationships between complementary differential outputs.
Typical uses include industrial RS-485 links, instrumentation equipment, building controls, factory automation networks, and low-power embedded communications. The device is particularly appropriate where a compact multipoint bus must operate from a 3.3 V supply and where low standby current matters. Its transmitter can also be used in full-duplex point-to-point configurations when separate differential pairs are available.
The principal design consideration is that the 12-pin PDIP package occupies more board area than leadless surface-mount alternatives. Place the transceiver close to the connector and bus interface, maintain the differential pair as a tightly coupled route, and provide the termination and biasing required by the RS-485 network. Keep the logic side and cable-side return paths separated to avoid introducing ground potential differences into the differential receiver.
This page combines the manufacturer's key electrical ratings with practical guidance for RS-485 bus implementation, package selection, transient protection, and power management. It also identifies the temperature-grade ADM3491AN-1 as a same-package option for design continuity when its specified operating grade matches the system requirements.
Alternativas directas para ADM3491AN — mismo encapsulado, compatible pin a pin. Se excluyen las piezas de otro encapsulado que requieren retrabajo de la PCB.
ADM3491AN-1
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
ADM3491AN Especificaciones
| Tensión de alimentación | 3.3 V ± 0.3 V |
| Velocidad de datos | 20 Mbps |
| Corriente de alimentación | 840 µA |
| Corriente de apagado | 2 nA |
| Receiver Input Impedance | 19 kΩ |
| Maximum Transceivers on Bus | 50 transceivers |
| Duplex Mode | Full duplex |
| Interface Standards | EIA RS-485 and EIA RS-422 |
| Logic Compatibility | Interoperable with 5 V logic |
| Fault Protection | Short-circuit protection and thermal shutdown |
| Transient Immunity | IEC 1000-4-4 above 1 kV |
| Transmitter Skew | 8 ns |
| Encapsulado | 12-pin PDIP |
| Tipo de montaje | Through-hole |
Configuración de pines de ADM3491AN
| Pin 1 | RO — Receiver output |
| Pin 2 | RE — Receiver enable, active low |
| Pin 3 | DE — Driver enable |
| Pin 4 | DI — Driver input |
| Pin 5 | GND — Ground |
| Pin 6 | Y — Non-inverting driver output |
| Pin 7 | A/Z — Non-inverting receiver input and inverting driver output |
| Pin 8 | B — Inverting receiver input and non-inverting driver output |
| Pin 9 | VCC — Positive supply |
| Pin 10 | NC — Not connected |
| Pin 11 | NC — Not connected |
| Pin 12 | NC — Not connected |
Aplicaciones típicas
ADM3491AN es adecuado para 6 aplicacións: Industrial RS-485 Sensor Networks, Battery-Powered Field Instruments, Building and HVAC Control Networks, Test and Measurement Equipment, Factory Automation Equipment, Point-to-Point High-Speed Data Links.
Industrial RS-485 Sensor Networks
The ADM3491AN fits 3.3 V industrial sensor networks where multiple remote nodes must communicate over a shared differential bus. Its 20 Mbps maximum data rate supports higher-speed telemetry, while 840 µA operating current and 2 nA shutdown current help control consumption at remote nodes. The 19 kΩ receiver input impedance permits a bus population of up to 50 transceivers under specified conditions. In a multi-drop installation, enable only the driver belonging to the active node to prevent bus contention, and calculate termination and fail-safe biasing for the complete cable network.
Recomendado
Battery-Powered Field Instruments
The ADM3491AN is useful in portable field instruments that need reliable RS-485 communication without continuously draining the battery. Its 840 µA supply current is suitable for a low-power 3.3 V system, and the 2 nA shutdown specification allows the transceiver to be disabled between measurement or configuration intervals. Use the shutdown function when the bus is inactive, but account for the receiver’s continuous bus loading and external pull-up or pull-down currents when calculating standby consumption. The 20 Mbps capability also allows the same device to support a high-rate configuration link.
Recomendado
Building and HVAC Control Networks
The ADM3491AN supports full-duplex RS-485 links used by building controllers, HVAC equipment, and environmental monitoring modules. A 3.3 V supply requirement integrates readily with modern embedded controllers, while the stated 19 kΩ input impedance supports larger multipoint networks. The transmitter’s 8 ns skew specification helps preserve timing between complementary outputs, and short-circuit protection plus thermal shutdown improve robustness on field wiring. Protect the connector-side interface with an appropriate surge and ESD network because industrial building cables may extend beyond the equipment enclosure.
Recomendado
Test and Measurement Equipment
The ADM3491AN is appropriate for programmable instrumentation that uses RS-485 for remote control, synchronization, or data acquisition. Its 20 Mbps data rate can shorten transfer time when the host gathers high-volume samples from multiple devices. Full-duplex operation is valuable when separate transmit and receive pairs are available, preventing the controller from waiting for bus turnaround. The 3.3 V architecture fits modern instrument logic, and 5 V logic interoperability allows connection to suitable control signals. Keep the differential route away from analog inputs and establish a clear grounding strategy at the connector.
Recomendado
Factory Automation Equipment
The ADM3491AN can serve as the bus interface in factory automation controllers, remote I/O modules, and motor-support equipment. Its 50-transceiver bus capability suits distributed wiring where numerous nodes share a communication line, while the 20 Mbps rating accommodates fast command and status traffic. Short-circuit protection and thermal shutdown are valuable when connected equipment has wiring faults. For a new PCB, preserve a robust RS-485 layout with a continuous ground reference, symmetrical differential routing, protection devices, and connector placement that minimizes stub lengths.
Recomendado
Point-to-Point High-Speed Data Links
Although RS-485 is widely used for multipoint buses, the ADM3491AN can also support high-speed point-to-point links when its full-duplex capability is used with separate differential pairs. The 20 Mbps maximum data rate provides useful margin for transferred blocks, configuration data, or real-time status information. Operate both ends from compatible 3.3 V supplies, match termination to the cable, and avoid long unbalanced branches. The 840 µA active current remains low enough for embedded links, while shutdown can isolate the transceiver when the link is intentionally inactive.
Recomendado
Resumen de productos recomendados
Datos de referencia de ingeniería para ADM3491AN — comparación, orientación de diseño e información de cumplimiento.
Guía de selección
Comparación con alternativas
| Parámetro | Este producto | ADM3491AN-1 |
|---|---|---|
| Brand | Analog Devices | Analog Devices |
| Package | 12-pin PDIP | 12-pin PDIP |
| Nominal Supply Voltage | 3.3 V ± 0.3 V | 3.3 V ± 0.3 V |
| Data Rate | 20 Mbps | 20 Mbps |
| Supply Current | 840 µA | 840 µA |
| Shutdown Current | 2 nA | 2 nA |
| Receiver Input Impedance | 19 kΩ | 19 kΩ |
| Maximum Bus Population | 50 transceivers | 50 transceivers |
| Duplex Mode | Full duplex | Full duplex |
| Interface Standards | EIA RS-485 and EIA RS-422 | EIA RS-485 and EIA RS-422 |
| Transient Immunity | IEC 1000-4-4 above 1 kV | IEC 1000-4-4 above 1 kV |
Diferenciadores clave
- Identical principal ratings in the closest drop-in option (frente a ADM3491AN-1)
- High bus population in a through-hole package (frente a ADM3491AN-1)
- Full-duplex operation with 5 V logic interoperability (frente a ADM3491AN-1)
Notas de diseño
Route the RS-485 differential pair as a tightly coupled pair with a continuous ground reference, and keep the two conductors over the same ground plane where practical. Connect the transceiver directly to the protection network and connector with minimal stubs. Avoid routing the pair alongside switching-converter paths, high-current relay traces, or analog input lines because differential signaling rejects common-mode noise but does not eliminate coupled differential interference.
Enable only one transmitter on a shared RS-485 bus at a time. The ADM3491AN provides separate receiver-enable and driver-enable controls, which allows the receiver to remain active while the driver is disabled. For a half-duplex implementation, combine the enable controls correctly so that the transmitter is not accidentally enabled while another node is transmitting; simultaneous active drivers can produce excessive bus current and unreliable communication.
Use a termination network matched to the physical bus rather than adding termination indiscriminately to every node. Long cables, unequal stub lengths, and unterminated branches increase reflections and can reduce the usable data rate below the 20 Mbps device rating. Place surge and ESD protection at the connector, keep the protection current away from sensitive logic ground paths, and verify the completed network with signal-integrity or compliance testing under the worst-case cable length.
The 3.3 V nominal supply has a stated tolerance of ±0.3 V, so design the rail to remain within the device specification across temperature, tolerance, and transient conditions. Place local decoupling close to the VCC and ground pins, and account for the transceiver’s 840 µA active demand in low-power budgets. Use the 2 nA shutdown mode when the bus interface is not needed, but verify that external pull networks do not dominate the system’s standby current.
Información de cumplimiento
The manufacturer documentation identifies IEC 1000-4-4 transient immunity above 1 kV. RoHS, REACH, lead-free, halogen-free, and conflict-minerals status were not explicitly stated.
