GENERAL DESCRIPTION

The ADM2483 differential bus transceiver is an integrated, galvanically isolated component designed for bidirectional data communication on balanced, multipoint bus transmission lines. It complies with ANSI EIA/TIA-485-A and ISO 8482: 1987(E). Using the iCoupler technology from Analog Devices, Inc., the ADM2483 combines a 3-channel isolator, a three-state differential line driver, and a differential input receiver into a single package. The logic side of the device is powered with either a 5 V or 3 V supply, and the bus side uses a 5 V supply only.

The ADM2483 is slew-limited to reduce reflections with improperly terminated transmission lines. The controlled slew rate limits the data rate to 500 kbps. The device’s input impedance is 96 kΩ, allowing up to 256 transceivers on the bus. Its driver has an active-high enable feature. The driver differential outputs and receiver differential inputs are connected internally to form a differential input/output (I/O) port.

When the driver is disabled or when VDD1 or VDD2 = 0 V, this imposes minimal loading on the bus. An active-high receiver disable feature, which causes the receive output to enter a high impedance state, is provided as well.

The receiver inputs have a true fail-safe feature that ensures a logic-high receiver output level when the inputs are open or shorted. This guarantees that the receiver outputs are in a known state before communication begins and at the point when communication ends.

Current limiting and thermal shutdown features protect against output short circuits and bus contention situations that might cause excessive power dissipation. The part is fully specified over the industrial temperature range and is available in a 16-lead, wide body SOIC package.

 

FEATURES

RS-485 transceiver with electrical data isolation

Complies with ANSI TIA/EIA RS-485-A and ISO 8482: 1987(E)

500 kbps data rate

Slew rate-limited driver outputs

Low power operation: 2.5 mA max

Suitable for 5 V or 3 V operations (VDD1)

High common-mode transient immunity: >25 kV/μs

True fail-safe receiver inputs

Chatter-free power-up/power-down protection

256 nodes on bus

Thermal shutdown protection

Safety and regulatory approvals

UL recognition: 2500 V rms for 1 minute per UL 1577

CSA Component Acceptance Notice 5A

IEC 60950-1 800 V rms (basic), 400V rms (reinforced)

VDE Certificate of Conformity

DIN V VDE V 0884-10 (VDE V 0884-10): 2006-12

VIORM = 560 V peak (reinforced)

VIORM(DC) = 1500 V dc

CQC certification per GB4943.1-2011

Operating temperature range: −40°C to +85°C

 

APPLICATIONS

Low power RS-485/RS-422 networks

Isolated interfaces

Building control networks

Multipoint data transmission systems

 

GENERAL DESCRIPTION

The ADM2483 differential bus transceiver is an integrated, galvanically isolated component designed for bidirectional data communication on balanced, multipoint bus transmission lines. It complies with ANSI EIA/TIA-485-A and ISO 8482: 1987(E). Using the iCoupler technology from Analog Devices, Inc., the ADM2483 combines a 3-channel isolator, a three-state differential line driver, and a differential input receiver into a single package. The logic side of the device is powered with either a 5 V or 3 V supply, and the bus side uses a 5 V supply only.

The ADM2483 is slew-limited to reduce reflections with improperly terminated transmission lines. The controlled slew rate limits the data rate to 500 kbps. The device’s input impedance is 96 kΩ, allowing up to 256 transceivers on the bus. Its driver has an active-high enable feature. The driver differential outputs and receiver differential inputs are connected internally to form a differential input/output (I/O) port.

When the driver is disabled or when VDD1 or VDD2 = 0 V, this imposes minimal loading on the bus. An active-high receiver disable feature, which causes the receive output to enter a high impedance state, is provided as well.

The receiver inputs have a true fail-safe feature that ensures a logic-high receiver output level when the inputs are open or shorted. This guarantees that the receiver outputs are in a known state before communication begins and at the point when communication ends.

Current limiting and thermal shutdown features protect against output short circuits and bus contention situations that might cause excessive power dissipation. The part is fully specified over the industrial temperature range and is available in a 16-lead, wide body SOIC package.

 

More Information

ELECTRICAL ISOLATION

In the ADM2483, electrical isolation is implemented on the logic side of the interface. Therefore, the part has two main sections: a digital isolation section and a transceiver section . Driver input and data enable signals, applied to the TxD and DE pins, respectively, and referenced to logic ground (GND1), are coupled across an isolation barrier to appear at the transceiver section referenced to isolated ground (GND2). Similarly, the receiver output, referenced to isolated ground in the transceiver section, is coupled across the isolation barrier to appear at the RxD pin referenced to logic ground.

iCoupler Technology

The digital signals are transmitted across the isolation barrier using iCoupler technology. This technique uses chip scale trans former windings to couple the digital signals magnetically from one side of the barrier to the other. Digital inputs are encoded into waveforms that are capable of exciting the primary trans former winding. At the secondary winding, the induced waveforms are then decoded into the binary value that was originally transmitted.

THERMAL SHUTDOWN

The ADM2483 contains thermal shutdown circuitry that protects the part from excessive power dissipation during fault conditions. Shorting the driver outputs to a low impedance source can result in high driver currents. The thermal sensing circuitry detects the increase in die temperature under this condition and disables the driver outputs. This circuitry is designed to disable the driver outputs when a die temperature of 150°C is reached. As the device cools, the drivers are re-enabled at a temperature of 140°C.