Isolated Power Interfaces
IsoLoop Isolators are the ideal alternative to optocouplers for Isolated Power
Interfaces. Current-drive inputs replace LED inputs. Open-drain outputs replace
open-collector phototransistors. Unlike optocouplers, however, IsoLoop Isolators
have unlimited life with no degradation. IsoLoop Isolators reduce board space
with up to two channels per MSOP.
Illustrative circuits:
 Application
Bulletin: IsoLoop Isolators for High-Efficiency Power Control
IL600-Series
Passive-Input Isolator data sheet
IL600A-Series
Open-Drain Isolator data sheet
Switch-Mode Power Supply Gate Driver with an IL711 Isolator
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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Isolated Relay Driver
with an IL711 Isolator
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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Isolated Power Control Using IL610s
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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Multi-Channel Isolated Alarm Monitor Using IL610As
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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Diode Protection to Extend
IL6xx Input Range
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. Back to top
CLDs Extend IL6xx Input Range
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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Isolated 120 VAC Line Monitor Using IL610A
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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