Galvanically isolated discrete-to-digital sensor for aircraft and avionics systems introduced by Holt

June 1, 2022
Two sense modes are for 5- and 28-volt systems; low-threshold mode for detecting voltage levels, and 5-volt aircraft systems such as MIL-STD-1760.

MISSION VIEJO, Calif. – Holt Integrated Circuits in Mission Viejo, Calif., is introducing the HI-8427 galvanically isolated discrete-to-digital sensor for a variety of aircraft and avionics systems.

The HI-8427 provides 400 volts galvanic isolation between the sense inputs and the digital logic and two ground and open sensor modes, one for sensing analog inputs in the 0 to 5-volt range and the other for sensing inputs compliant to Airbus ABD0100 specification threshold levels found in 28-volt aircraft and avionics systems.

The 400-volt galvanic isolation is provided by a capacitively coupled isolation barrier between the analog sense inputs and digital outputs, ensuring protection of sensitive digital circuitry.

All sensor inputs are designed to comply with the power transient requirements outlined in MIL-STD-704. The 6.5-by-6.5-millimeter thermally enhanced TSSOP-20 package provides a compact footprint for a six-channel device, which normally requires discrete components and significant board space.

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The two sense modes provide flexibility for use in 5- and 28-volt systems. Low-threshold mode may be used for detecting voltage levels in CMOS or TTL applications and 5-volt aircraft systems such as MIL-STD-1760 address line or similar discrete voltages.

Ground levels are sensed at voltages less than 1.5 volts and result in a logic "0" on the digital output. Open or high levels are detected at voltages more than 4.0 volts, resulting in a logic "1" on the digital output.

When all sense inputs are open, a disconnect digital output will be asserted and a dead face digital input is also provided to disconnect all sense inputs simultaneously. A 5-milliamp wetting current is sourced when any of the sense inputs are at ground potential, making this device suitable for detecting relay contact switching.

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Standard threshold mode provides Ground detect below 4.5 volts and open detect at voltages greater than 10.5 volts, compliant with Airbus ABD0100 specification, making this mode suitable for 28-volt aircraft systems.

The device is available in industrial versions that operate in temperatures from -40 to 85 degrees Celsius; and in extended temperature ranges of -55 to 125 C temperature ranges with optional burn-in at the higher temperature. Samples are available from Holt on request.

For more information contact Holt Integrated Circuits online at

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