This week, X-FAB Silicon Foundries SE released news that it was going into production with a new galvanic isolation semiconductor process for manufacturing.

X-FAB is a specialty foundry group for analog/mixed-signal semiconductor applications. This week, they announced a new high-voltage process for galvanic isolation of circuits that's suitable for the rugged and highly-regulated applications of the automotive industry.

According to the company's website, X-FAB's focus on developing technologies for analog and mixed-signal circuits means that this new galvanic isolation method is not intended for digital applications:

"These technologies are not intended for digital applications with the smallest possible structure sizes, but rather are targeted for analog applications that can be integrated with additional functions such as high voltage, non-volatile memory or sensors."

 

X-FAB’s high-voltage galvanic isolation technology. Image courtesy of X-FAB

 

The announcement of the new process is heralded by the release of two test chips to facilitate quick evaluations of the new process by OEMs worldwide:

  • G3-C1 works by capacitive coupling. There is an isolation thickness of 11µm and is able to withstand 6,000 VRMS.
  • G3-T06 works by inductive coupling. This offers an isolation layer thickness of 14 µm.

 

Automotive Qualifications and Notes

In addition to ground isolation, galvanic isolation plays an important role in improving noise immunity, critical in the electrically and mechanically noisy automotive environment that X-FAB has qualified their new process for.

Notably, the new release does not include an opto-isolator methodology. That technique, while appropriate in many areas, may not be able to offer suitable reliability in high-temperature environments that demand high data transmission rates.

X-FAB's new process yields devices able to operate at 175°C, with support for working voltages of up to 1.7 kV.

 

Standards Compliance for the X-FAB Galvanic Isolation Process

Compliance testing doesn't just apply to components, but also to the processes that create the materials they're made from. 

X-FAB's new process claims to meet the IEC 60747-17 semiconductor coupler draft standard, which is designed to ensure isolation for safety purposes.

The company's Dresden facility is also certified for automotive manufacturing in accordance with the IATF-16949:2016 International Automotive Quality Management System (QMS) standard.

Design kits are available now for all EDA (electronic design automation) platforms. These can be downloaded from X-FAB’s customer web portal.

In addition to test chips, process qualification reports are also available.

 

What Is Galvanic Isolation?

The simplest way to think of galvanic isolation is in terms of a simple power supply where the input is the AC power mains.

 

Galvanic isolation effected via a transformer

 

Even if the output voltage of the transformer is the same as the input, it still serves an important function—the Earth ground in the primary circuit is completely isolated from the chassis ground on the secondary side.

The safety implications here are obvious, but the principle is the same in any situation that requires that different grounds within the same system must be kept at different electrical potentials.

 

Methods of Achieving Galvanic Isolation

There's more than one way to isolate a circuit. Here's a quick look at other methods of isolation:

  • Capacitors. These allow AC signals to pass but block DC signals can also be used to achieve galvanic isolation.
  • Opto-isolators. The source of a signal can turn on a LED in the transmitting end of an opto-isolator, and a photosensitive device in the receiving end registers its presence. There is no electrical connection at all between the two halves of the unit.
  • Hall Effect Sensors. These are devices whose output voltage varies in proportion to an applied magnetic field. Again, these are devices with no electrical connection at all between input and output.

For further description of the varied methods of achieving optical isolation, see our article on the purposes and methodologies of galvanic isolation.

 

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