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[FAQ] UCC21530: Can UCC21530 and UCC21540 DWK packages be used in 800V systems?

Part Number: UCC21530
Other Parts Discussed in Thread: UCC21540

As 800 V systems are becoming more common it is important to not only consider the voltage from the primary to secondary side of a driver, but also the channel to channel voltage, at least with dual channel devices. For example, in a traditional buck converter, the maximum channel to channel voltage applied to the driver is the full DC bus voltage, which can sometimes be up to 800V. Can TI's UCC21530 and UCC21540 parts handle this voltage?

  • The datasheet for UCC21530 specifies that the device can handle a channel to channel working voltage of up to 1850V, with the UCC21540 datasheet providing a similar value. This means that internally the devices can handle 800V with no problems. This internal voltage rating, however, is not the only consideration. The actual channel to channel voltage is generally limited by the standards that the system must meet, which often specify minimum creepage values for different voltages under different conditions. For example, one of the most common standards is IEC60664, which specifies minimum creepage in table F.4. According to this standard, the DWK package which has a channel to channel creepage of 3.3mm, can handle up to approximately 650 Vrms with a pollution degree of two, or 1000 Vrms with a pollution degree of one. Understanding the pollution degree and system requirements is the responsibility of the engineer working on the project.

    There are a few ways to handle these creepage requirements in high voltage systems. The first is to use a conformal coating, which can either enforce a pollution degree of one, or even remove the creepage requirement completely. The second method is to use a topology which limits the channel to channel voltage, even in 800 V systems. Finally, two single channel drivers such as the UCC53xx family can be used, allowing the engineer to choose the channel to channel spacing.

    References & additional resources