The HI-8427, Holt's newest addition to its galvanically isolated discrete-to-digital sensor family

Holt releases 6-channel Discrete-to-Digital sensor with 400V galvanic isolation and two GND/Open sense modes.

The HI-8427 provides 400V galvanic isolation between the sense inputs and the digital logic and two GND/Open sensing modes, one for sensing analog inputs in the 0 to 5V range and the other for sensing inputs compliant to Airbus ABD0100 specification threshold levels found in 28V aircraft systems.

The 400V 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 sense inputs are designed to comply with the power transient requirements outlined in MIL-STD-704. The small 6.5mm x 6.5mm thermally enhanced TSSOP-20 package provides a very compact footprint for a 6-channel device, normally requiring a multitude of discrete components and significant board space.

The device is available in industrial −40°C to +85°C and extended −55°C to +125°C temperature ranges with optional burn-in at the higher temperature.

The two sense modes provide flexibility for use in both 5V and 28V systems. Low Threshold mode may be used for detecting voltage levels in CMOS or TTL applications and 5V aircraft systems such as MIL-STD-1760 address line or similar discrete voltages. Ground levels are sensed at voltages <1.5V and result in a logic “0” on the digital output. Open or high levels are detected at voltages > 4.0V, 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 simultaneously disconnect all sense inputs. A 5mA wetting current is sourced when any of the sense inputs are at ground potential, making this device suitable for detecting relay contact switching. Standard Threshold mode provides Ground detect below 4.5V and Open detect at voltages greater than 10.5V, compliant with Airbus ABD0100 specification, making this mode ideal for 28V aircraft systems.

“This new device provides our customers with a flexible sensor, ideal for both 5V and 28V aircraft systems, galvanic isolation between the analog inputs and digital logic protects sensitive digital circuitry against unwanted transients.”

Anthony Murray, Director of Marketing Communications at Holt Integrated Circuits

Features

• 6-Channel galvanically isolated GND/Open discrete-to-digital sensor
• 400V isolation between sensor inputs and the logic interface
• In Low Threshold Mode, DISCONNECT signal indicates all sense input lines are “Open” (all digital outputs read logic “1”)
• Wetting current of 5mA provided in Low Threshold Mode
• Standard Mode detects Airbus ABD0100H and MIL-STD-704 standard compliant sensor thresholds with 1mA wetting current
• Robust Silicon-On-Insulator (SOI) CMOS technology
• In Standard Mode, sense inputs are lightning protected to RTCA/DO-160G, Section 22, Level 3 with external 470 Ohm resistor
• Supports 28V analog supply
• Withstands inadvertent application of 115 Vrms (60 - 400 Hz) power to sense inputs
• 3.3V, 2.5V or 1.8V compatible logic levels
• Compact thermally enhanced TSSOP package
• Single die for improved reliability and component and space saving
• Industrial and extended temperature ranges
• Burn-in available

Samples and further technical information on the HI-8427 can be requested by speaking to a member of our high-reliability components team. With a long history and technical expertise in civil and defence avionics, our team can also advise on Holt's ARINC 429, CAN, MIL-STD-1553 and other product lines.