Quad-Channel Digital IC Isolators Address Hybrid-Electric Vehicles

Expanding the company’s portfolio of AEC-Q100 qualified products for hybrid-electric vehicles (HEVs), the Analog Devices ADuM540xW family of quad-channel digital isolators provide magnetic isolation for high voltages up to 600 V, a safety and reliability requirement in HEVs, as well as data-signal isolation. The devices are based on Analog Devices’ iCoupler technology, which fully isolates data and power in a single package that cuts costs. The AEC-Q100 specification requires an operating temperature range from –40°C to 105°C.

The AMD5401W, AMD5402W, and AMD5403W are essentially integrated dc-dc converters. Each produces a 5-V output, regulated to within 1 mV/V for line and 1% for load conditions, with up to 500 mW of output power. This level of integrated isolation allows for power to be transferred across an isolation barrier, ensuring that the vehicle’s battery is monitored without drawing power from the battery itself. With four independent channels of isolation, the quad isolators fit well with circuitry using the Serial Peripheral Interface (SPI) ports. Channels can be configured in a variety of different ways as well as data rates. The devices also are compatible with RS-422 and RS-485 interface ports.

All three versions operate at switching rates from dc to 25 Mbits/s and differ in input and output current ratings. They’re specified to accept 68, 71, and 75 mA of input current, respectively, and output currents of 87, 85, and 83 mA, respectively (at 25 Mbits/s). Each is packaged in a 16-lead 10- by 10-mm small-outline IC (SOIC) surface-mount package with 7.5-mm creepage (Fig. 1).

Designed for harsh automotive environments, they withstand temperatures up to 105°C and feature high common-mode transient immunity of more than 25 kV/µs. They meet critical safety and regulatory requirements such as withstanding 2500 V RMS for 1 minute per the UL 1577 standard. Also, they meet the requirements of CSA Component Acceptance Notice #5A. The European VDE certificate of conformity is pending.

A NOVEL ISOLATION CONCEPT

The couplers are based on Analog Devices’ proprietary and novel integrated transformer-based iCoupler technology. It offers all the advantages of conventional optical, discrete-transformer, and semiconductor technologies without their size, cost, and performance limitations.

Isolation is achieved through the use of a 20-µm thick polyimide insulation layer between two transformer coils made of aluminum and gold materials (Fig. 2). This technology uses patented refresh circuitry to avoid the inherent instability of discrete transformers and achieve correct dc levels. Analog Devices uses the trademarked term “isoPower” to describe this power isolation method.

“Our isoPower devices provide users with not only a smaller component count and less pc-board space than conventional approaches, but also much less power consumption,” says David Krakauer, product line manager for the iCoupler isolation Group. “Compared to an optocoupler approach, power savings of 50% can be achieved. You need only 16 by 10 mm of board space with our part versus 17 by 34 mm for the optocoupler method, which requires the use of many more discrete components.”

“These advantages help car manufacturers build even more environmentally sound vehicles,” says Thomas Wessel, vice president of the automotive segment group.

The ADuM540xW isoPower digital isolators also suit industrial field-bus isolation applications, power-supply bias and gate drives, isolated sensor interfaces, and industrial programmable-level controllers (PLCs). They can operate with other Analog Devices components, including the ADuM7280 lithium-ion (Li-ion) battery monitoring system, and are compatible with earlier-version ADuM120/130/140xW digital isolators. 

All three ADMu540xW isolators are available in sample quantities. They cost $5.75 each in 10,000-unit quantities.

Analog Devices