An IL711 isolates the PWM Controller from the MOS gate driver for synchronous rectification. The IL711’s 0.3 ns pulse-width distortion and 100 ps jitter improve precision, minimize MOSFET dead time, and maximize system efficiency. Low EMI, transient immunity of 50 kV/µs, and barrier life of 44000 years make IsoLoop isolators ideal for this application.

The IL711V-1E provides two-channels and full 2.5 kV isolation in an ultraminiature MSOP-8 package, allow the designer to squeeze more into less board area. The wide-body IL711VE provides 5 kV isolation and best-in-class 1 kV Working Voltage in a true 8 mm creepage package.

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IsoLoop isolators have the speed, output current, and capacitive load capabilities to drive inexpensive power MOSFETs without additional circuitry. A 3-5 volt supply for the isolator is needed to drive the MOSFET gates (provided in this circuit by an NVE DC002-10E).

A variety of IL7xx-Series isolators can be used depending on the channels and isolation voltage needed.

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The fail-safe output (logic high output for zero coil current) of IL600 Isolators ensures the power FETs will be off on power-up. The IL600 inputs can be configured for inverting or non-inverting operation (see IL600 Product Data Sheet). The IL600 Isolators provide 2.5 kVrms isolation (1 minute), and 20 kV/µs transient immunity.

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IL600A Isolators’ open-drain outputs can be wire-OR connected. A very wide input voltage range is possible, and inputs can be configured for inverting or non-inverting operation (see IL600A Product Data Sheet). This illustrative circuit provides fail-safe output (logic high output for zero coil current), 2.5 kVrms isolation, and 20 kV/µs transient immunity. Typical logic output sink current is 10 mA for each isolator. Unlike optocouplers, IsoLoop Isolators do not degrade over time and have unlimited life.

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The 3.3 kilohm resistors ensure at least 5 mA of coil current for 20 volt inputs. The diodes limit the coil voltages to approximately 0.7 volts, providing 22 mA coil current at the 31 ohm minimum coil resistance over the temperature range, and 5.5 mA at the 128 ohm maximum coil resistance. Thus the coil current is between the 5 mA maximum input threshold (with a 5 volt supply) and the 25 mA Absolute Maximum coil current. This method allows very high input voltages, although the drive current can be high.

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CLDs limit the coil currents to less than the Absolute Maximum of 25 mA, and also limit loading of the input sources. The isolator will switch with an input voltage as low as approximately 1 volt, and the voltage can go as high as the CLD peak operating voltage of 45 volts, providing more than a 40:1 input range.

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The wide input voltage range of IL600 Isolators allows connection to line voltage through current-limiting resistors. Unlike optocouplers, input voltage can reverse without damaging the inputs. In this illustrative circuit, “Monitor Out” goes low when line voltage drops significantly. The 74HC123 monostable converts the 60 Hz isolator output to a monitor signal.

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