Electronic Design

Higher-V<sub>BR</sub> MOSFETs Open New Design Opportunities

Several MOSFETs with higher breakdown voltages have hit the market. Some are rated for 40, 60, and 80 V, which is 10 V higher than existing devices in their respective classes, with significantly lower conduction losses. Others are rated for 900 V, again with improved conduction loss specs.

At the high end of the breakdownvoltage range, Infineon Technologies is pushing the envelope with the industry’s first 900-V superjunction MOSFETs (see the figure). Potential applications for these new members of the company’s CoolMOS line include quasi-resonant flyback supplies in LCD TVs and simpler, cheaper, single-transistor forward (STF) supplies in PC “silver-boxes.”

In solar power generation systems, MOSFETs with 900-V breakdown voltages allow photovoltaic converter panels to be connected in series rather than in parallel, slashing cabling power losses and costs. In addition, 900-V devices are handy in designing power-factor correction circuits, enabling the use of higher voltages inside the supply.

Getting to 900 V isn’t easy. Generally, every doubling of voltage-blocking capability in a MOSFET technology leads to a fivefold increase in RDS(ON). Infineon isn’t saying much about how it overcame this “silicon limit,” but the datasheets describe on-state resistances of 0.12 O in TO-247s, 0.34 O in TO-220s, and 1.2 O in D-PAKs.

Samples of the 900-V, 340-mO devices in TO-220, TO-220FP, and TO-247 packages and a 1200-mO part in a D-PAK are available. The full family will be available later in the year. Representative pricing for a 120-mO MOSFET in a TO-247 package is less than $3.50. (Pricing is pegged to the Euro.)

Infineon has also added 40-, 60-, and 80-V breakdown-voltage families to its OptiMOS3 N-channel MOSFET line. Each family provides significantly lower conduction losses than existing alternatives, with higher breakdown ratings. The 40-V family was developed for switching supplies in printers, nonisolated industrial converters, and isolated dc-dc converters, where designers have been using MOSFETs rated for 30-V VBR. RDS(ON) specs are as low as 1.6 mO.

Continuous current rating is 100 A thanks to an improved SO8 package, dubbed “SuperSO8,” which provides a 1-K/W thermal resistance There also is a smaller SSO8 package, as well as the same TO-packaging as the lower breakdown-voltage MOSFETs they’re intended to supplant, but that sacrifices some of that continuous current rating.

The 60- and 80-V OptiMOS3 families can be used for motor controls and drives for dc-dc brushless and brushed motors. The 80-V devices are also expected to find applications in telecommunications applications.

Again, conduction losses are lower than what is generally available now. In a TO-220 package, the 80-V MOSFETs are rated for 18-mO RDS(ON), with 100-A continuous current. The larger MOSFETs are additionally available in D-PAKs and low-height D2-PAKs, which Infineon is licensing from International Rectifier.

Members of the 60-V family are shipping in production quantities, with the 40- and 80-V families sampling in 10,000-unit quantities. Unit pricing for the 40- and 60-V devices at the lowest RDS(ON) and highest continuous current ratings is less than $1. For the 80-V devices, unit pricing is under $2.


TAGS: Components
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