powerZONE Products for the week of November 22, 2004
Vishay Says . . .
MBRF20H20: Dual Schottky Rectifiers Feature 200-V
Reverse Voltage and 20-A Forward Current
Vishay Intertechnology, Inc. announced three new dual high-voltage Schottky rectifiers offering a 200-V reverse voltage - the highest available voltage for a silicon Schottky rectifier - a 20-A forward current rating, and a high maximum operating junction temperature of 175 °C.
Outperforming 200-V forward voltage Schottky rectifiers built on silicon carbide technology at a fraction of the cost, these new silicon-based devices are designed for secondary rectification of ac-to-dc and dc-to-dc converters with outputs up to 48 V, as well as freewheeling and polarity protection applications. Package options are the TO-220AB (MBR20H200CT), isolated TO-220AB (MBRF20H200CT), and TO-262AA (MBRB20H200CT-1).
With a low typical forward voltage drop of 0.65 V at 10 A and 125 °C,
small 1-mA maximum reverse leakage current at 125 °C, and high 290-A
forward surge current per leg, these new Schottky rectifiers have been optimized
for 50-W to 250-W power supply applications. They also feature a large peak
non-repetitive reverse surge energy of 20 mJ at 8/20 µs per leg.
analogZONE Says...
200-V reverse voltage (repetitive) and 20-A forward current from silicon! Vishay sometimes astounds us with how advanced and dedicated some of their processes are.
There are no recovery times quoted in the Vishay data sheet (but the voltage rate of change -- dv/dt -- is given as 10,000 V/µs) and that is probably the only area where SiC will marginally win out in a side-by-side race. Where Vishay is brilliant is in the derating of the devices over temperature: whichever package you use there is no derating of the forward current until over 125°C. A typical SiC product such as the CSD20030 from Cree (300 V, 20 A) http://www.cree.com/ftp/pub/CSD20030.PDF derates (Fig. 3) right from 25°C and at 125°C it is derated by over 25%.
The two diodes in each device have a common cathode configuration (to the case) for a positive output tap. Over-voltage protection is provided by a guardring while junction capacitance is 250 pF at 4 V, 1 MHz and falls to about 50 pF at 100 V, the kind of numbers you would expect from a power Schottky.
These devices completely knock SiC off the shelf with pricing such manufacturers could not possibly, profitably, achieve. It hardly goes without saying that these rectifiers will sell by the millions. They will end up in 48-V power supplies, consumer display products, and many other switching supply applications where higher switching frequencies are preferred.
Three T0-220-type packages are offered for the devices: TO-220AB, ITO-220AB and the tabless TO-262AA.
The three versions of the MBR20H20 are in production and they are priced at $0.80 in 1000-piece lots.