ADM2587EBRWZ-REEL7 Fully Isolated RS-485 High-Speed Transceiver

What is ADM2587EBRWZ-REEL7 and what the "REEL7" means?

ADM2587EBRWZ-REEL7 is a power isolation data transceiver packaged as SOIC-20, featuring ±15 kV electrostatic discharge (ESD) protection and suitable for high-speed communication on multi-point transmission lines. ADM2587E integrates an isolated DC-to-DC power supply, eliminating the need for an external DC-to-DC isolation module. It supports a single 5 V or 3.3 V power supply and provides a complete signal and power isolation RS-485 solution. The device incorporates iCoupler® technology, integrating 3-channel isolators, tri-state drivers, differential input receivers, and isoPower converters. It includes current limiting and thermal shutdown protection to ensure safe operation.
The suffix "-REEL7" indicates the packaging/form factor, provided in a complete reel format, suitable for surface mount automated printed circuit board assembly.

The working principle of ADM2587E

The ADM2587E is an isolated transceiver that integrates RS-485 communication + signal isolation + power isolation completely. Its working principle can be divided into three core parts:

1. iCoupler® Signal Isolation Principle

The signal isolation of the ADM2587E is implemented on the logic side of the interface: The signals on the TxD/DE pins are transmitted through the isolation layer to the transceiver part, and the received signals of the transceiver also return through the isolation layer to the RXD pin to achieve signal isolation between the logic and the isolated ground.

2. isoPower® Power Isolation Principle

The power isolation of the ADM2587E is achieved through the integrated isoPower isolated DC-to-DC converter: The VCC power supplies the oscillation circuit and injects current into the chip-level air-core transformer, and the energy transmitted to the secondary is rectified and stabilized to output 3.3 V. The secondary controller generates PWM control signals to regulate the output and provides real-time feedback to improve power and efficiency.

3. RS-485 Transceiver Circuit Working Principle

The isolated signals and power are transmitted to the RS-485 bus:

• Differential Driver (Driver)
• Converts digital signals to RS-485 differential voltages (A/B lines).
• Supports tri-state output (enable/disable).
• Has overcurrent protection, short circuit protection, and thermal shutdown.
• Differential Receiver (Receiver)
• Receives the differential signals on A/B.
• Converts them to logic high and low levels and outputs them to the isolated side.
• The receiver can be disabled, and the output enters a high-impedance state.

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Overall workflow

1. Input signal → iCoupler isolation → Driver output to bus
2. Bus differential signal → Receiver → iCoupler isolation → Output signal
3. isoPower transforms and isolates the input power → Supplies power to the isolated side circuit

The insulation life-limiting factors of ADM2587E

All insulation structures will eventually break down when subjected to voltage stress for a sufficient period of time. The rate of insulation aging depends on the voltage waveform characteristics applied across the insulation terminals. The long-term reliability of ADM2582E depends on the waveform type across the isolation voltage. Different waveforms cause varying degrees of damage to the insulation and have different impacts on the allowable maximum operating voltage and lifespan.

1. Insulation ages over time and ages under long-term voltage stress. The aging rate of the insulation structure varies depending on the waveform type, being closely related to voltage waveforms such as AC/DC, bipolar/single-polarity, etc.
2. Bipolar AC voltage is the most demanding environment. Bipolar AC waveforms cause the greatest damage to insulation. Therefore, achieving a 50-year lifespan under bipolar AC conditions determines the maximum operating voltage recommended by Analog Devices.
3. Insulation damage is minimal under single-polarity AC or DC voltage. Thus, it is possible to achieve at least a 50-year lifespan at higher operating voltages.

APPLICATIONS

application example

1. Isolated RS-485/RS-422 interfaces
2. Industrial field networks
3. Multipoint data transmission systems

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Typical applications

The DM2587E can be used in half-duplex or full-duplex RS-485 networks. Up to 256 transceivers can be connected. To reduce signal reflection, the characteristic impedance terminal should be used at the receiving end, and the branch lines should be kept as short as possible. In half-duplex mode, terminal matching is required at both ends of the line. The capacitor layout should refer to the PCB layout suggestions. The placement of the terminal resistors depends on the node position and the network topology.

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Common Questions about ADM2587EBRWZ-REEL7

1. What are the differences between ADM2587E and ADM2582E?

Both ADM2587E and ADM2582E integrate iCoupler signal isolation and isoPower power isolation. However, ADM2587E has a slightly higher data rate and drive capability, making it suitable for multi-point networks with higher bandwidth requirements.

2. Does ADM2587E require an external DC-DC converter?

No, ADM2587E has an internal isoPower DC-to-DC converter that can supply power to the isolated transceivers, simplifying the circuit design.

3. How does ADM2587E prevent bus short circuits or overcurrents?

• Built-in current limiting and thermal shutdown protection:
• Prevent the output circuit from shorting and damaging the device
• Automatically protect when bus competition leads to excessive power