feature

Insulation test voltage: to 3.5kV rms; five independent logic lines: there are six I/O configurations; logic signal bandwidth: 20MHz (min); CMV transient immunity: 10kV/ms min; waveform edge transmission symmetry: 61ns; Field and System Output Enable/Tri-State Capability; Performance Levels from -258C to +858C; UL1950, IEC950, EN60950 Certified (VDE, CE, Pending).

application

PLC/DCS analog input and output card; communication bus isolation; general data acquisition applications; IGBT motor drive control; high-speed digital I/O ports.

General Instructions

The AD261 is designed to isolate the connection of five digital control signals to a microcontroller and its associated field I/O components. Six models allow from five input lines to five output lines, including combinations in between. Each AD261 effectively replaces up to five opto-isolators.

Each line of the AD261 has a bandwidth of 20 MHz (minutes) and a propagation delay of only 14ns, which enables fast data transfer. Keeping the output waveform symmetrical within ±1ns of the input allows the AD261 to accurately isolate time-based PWM signals.

All field or system output pins of the AD261 can be set to a high tri-state level using the resistors of the two enable pins. Field Output 3 states provide a convenient way to preset logic levels on power-up using up/down resistors. The system side outputs are in three states, which is convenient for multiplexing multiple AD261s.

AD261 Class B isolation barrier 100% tested up to 3.5 kV rms (system to field). The barrier design also provides excellent common-mode transient immunity of 10 kV/µs field-side terminal common-mode voltage offset relative to the system side, with no false output triggering on both sides.

Each output is updated with input logic transitions in nanoseconds, and the AD261 also features a continuous output update feature that automatically updates each output input based on the DC level. This guarantees that the output is always active after 10 microseconds of fault state or after a power-on reset interval.

Product Highlights

Six independent logic line I/O configurations are available: The AD261 is available in six-pin compatible I/O configuration versions to meet a wide variety of requirements.

Wide Bandwidth with Minimal Edge Error: The AD261 offers very fast logic signal isolation bandwidth and 14ns propagation delay due to its 20MHz. It maintains a waveform input and output edge transition error is typically less than ±1ns (total) for positive and negative transitions.

3.5kV rms test voltage isolation rating: AD261B class rated voltage is 1.25kV rms, 100% production using standard ADI test method, tested at 3.5kV rms.

High Transient Immunity: The AD261 rejects common mode transients or damaged devices that rotate at speeds up to 10 kV/µs without false triggering.

AD261 configuration

Field and System Enable Features: The isolated and non-isolated sides of the AD261 have enable pins for all outputs. After re-enabling these pins, all outputs are updated to reflect the current input logic level.

CE Certification: Simply adding external bypass capacitors at the power pins, the AD261 can be used in most applications (complies with the EMC directive) and EN60950 guarantees low-voltage (safety) directive certification.

General properties

The AD261 provides five HCMO compatible isolated logic lines with common mode transient immunity ≥ 10kv/μs. The enclosure design and pin arrangement provide greater than 18 mm spacing between field and system side conductors, providing CSA/IS and IEC creepage distances compliant with 750 V mains isolation.

Five unidirectional logic lines have six possible combinations of "input" and "output" or transmitter/receiver pairs; therefore there are six AD261 part configurations (see Table 1).

Each 20MHz logic line has a Schmitt trigger input and a tri-state output (on the other side of the isolation barrier) with 14 ns propagation delay. The barrier makes all outputs on that side tri-state inputs (slave pins) ignore their inputs and retain their last input known state.

Note: All unused logic inputs (1-5) should be connected high or low, but not floating. Edge "fidelity," or the difference in propagation time between rising and falling edges, is typically less than ±1ns. Unlike opto-isolators, power consumption is a function of frequency of operation. Each logic line barrier driver requires about 160µA per MHz and each receiver 40µA per MHz, and of course 4mA total idle current (per side). The supply current decreases with increasing temperature (about -0.03%/°C).

The total capacitance across the isolation barrier is less than 10 lbf. The minimum period of a pulse that can be precisely coupled is about 25 nanoseconds across the obstacle. Therefore the maximum square wave operating frequency is 20 MHz.

The logic information is sent as "set high/set low" through the barrier data derived from the logic level transition of the input. After power-up or failure, the outputs may not represent the state of the isolator channel inputs. An internal circuit operates in the context of interrogating all inputs approximately every 5 microseconds, without logic transitions, through obstacles.

Therefore, the recovery time from a fault state or power-up is between 5 microseconds and 10 microseconds.

Dimensions

Dimensions are in inches and (mm).