Welcome. My name is Tom Bonifield. I am a high-voltage isolation technologist at Texas Instruments. And we are in one of the high-voltage labs at TI. This video is part of a series of videos on high-voltage reinforced isolation quality and reliability. This video is on the high-voltage isolation structure itself. 

Reinforced isolation technology at Texas Instruments is realized by using thick silicon dioxide capacitors combined in series. Each channel uses high-voltage isolation capacitors on both die. As you can see in the schematic cross-section in the upper left, where there is a die on the left side and a die on the right side, and each of them have a high-voltage capacitor. And they're connected in series. The combined isolation capacitor thickness is greater than 21 microns. 

Data is transmitted across the isolation barrier, as shown in the schematic on the upper right. Signal comes in, is modulated, goes across the barrier as part of a differential pair of capacitors, demodulated, and out. This same isolation communication path is used for digital isolators, for isolated links, for A to D converters, isolated amplifiers, and isolated gate drivers. The result of this structure is a very high isolation capability, 12.8 kV surge voltage rating, 8 kVpeak transient over-voltage, and 1.5 kVrms working voltage. 

Now let's dive into the structure. We'll start at the high level. What you're seeing is an X-ray image of a 16-pin SOIC package. This is a wide-body package in which there is 8 millimeters of creepage and clearance from the top of the picture to the bottom or usually called the left to the right. Inside the package, there's a large internal spacing of greater than 600 microns between the die pads. And on the die pads are two die, one on each side. Each have high-voltage capacitors, as you can see. This is a three-channel isolator, and you can see six capacitors on each side. 

Now let's dive into the isolation capacitor in detail. The reinforced isolation barrier consists of two of these high-voltage capacitors, one on each die connected in series. And each capacitor is a thick silicon dioxide capacitor dielectric. The dielectric is made up of multiple layers. Each of the layers is typical of the way integrated circuits are built in billions of units in the industry every year. 

Each layer is deposited silicon dioxide, deposited using chemical vapor deposition. Chemical vapor deposition is an atomic molecular deposition that builds up the silicon dioxide film. Before a second layer is added on top of another layer, the first layer is polished with a chemical mechanical polish planarization for good adhesion between layers. The result is a very thick silicon dioxide capacitor greater than 10.5 microns in total thickness for very high isolation voltage capability. 

One of the best tests for this is breakdown voltage test or ramp-to-breakdown test. In this test, an AC high-voltage stress is applied from the left side to the right side. That stress is ramped up at a rate of 1 kilovolt rms per second until breakdown occurs. When breakdown occurs, the breakdown voltage is recorded. This is repeated on a large population of units. From the statistics on those units, we can assess how well the technology performs relative to the rating. 

So in this graph, this is a histogram of 1,130 units that were tested for ramp-to-breakdown, taken from 113 lots. What you can see is that the average breakdown voltage is greater than 14 kilovolts per rms. That is a lot higher than the isolation rating of 5.7 kVrms. 

So a good way to judge how much higher it is is a metric called CPK. CPK of 1 means that the data is 3 sigma above the isolation requirement. A CPK of 2 means that the data is 6 sigma above the isolation rating. And as you can see, this dataset has a CPK greater than 6. And this CPK is measured to the production test condition, which is 20% above the isolation rating. 

This data demonstrates very high voltage isolation capability. In conclusion, TI's reinforced isolation family of products has high-voltage capability that exceeds the requirements for reinforced isolation. The quality of the high-voltage isolation is demonstrated by substantial margins using statistical test methods. For more details, you can go to ti.com/isolation to find the white paper enabling high-voltage signal isolation quality and reliability. Thank you.