powerZONE Products for the week of May 6, 2002
Siliconix Says . . .
Si4362DY/Si4892DY: Low-Side 30-V Power MOSFET and
Companion High-Side Device Provide High Efficiency in DC-to-DC Conversion
A new milestone in optimizing MOSFETs for core voltage DC-to-DC power conversion
was reached with the release of two advanced LITTLE FOOT devices by Siliconix
incorporated, an 80.4%-owned subsidiary of Vishay Intertechnology, Inc.
Latest in the Vishay Siliconix portfolio of constantly improving solutions for DC-to-DC converters, the new devices are a synchronous low-side power MOSFET (Si4362DY) and a control high-side power MOSFET (Si4892DY) that will deliver industry-best performance when used together in single or multiphase power supply circuits for notebook computers and game stations.
By key figures of merit, the new devices represent an improvement over previous-generation MOSFETs used for DC-to-DC conversion applications.
With an exceptionally low on-resistance rating of 6.25 milliohms at a 4.5-V gate drive - 17% lower than competing devices - the new Si4362DY is optimized for low-side operation, reducing conduction losses and thus boosting efficiency. Optimized for high-side operation, the Vishay Siliconix Si4892DY features a very low typical gate charge of 8.7 nC, minimizing switching losses, and on-resistance of 20 milliohms at a 4.5-V gate drive.
The new low-side Si4362DY also features a gate-drain-to-gate-source charge ratio of 0.6 - 25% better than competing devices - and a very low gate resistance of 1.3 ohms, both characteristics that help to prevent "shoot-through" conditions in which the high- and low-side MOSFETs are on, creating a short from the input voltage to ground.
Improving on its predecessor, the Si4894DY, the new Si4892DY features a lower gate resistance of 1 ohm, a 30% better on-resistance times gate charge product of 139.2, and faster turn-on times. The device's low switching losses and higher speeds combine to provide higher efficiency control.
Working together, the two 30-V MOSFETs provide increased efficiency,
longer run times, and cooler operation for portable computers and game consoles.
The new devices' low gate-drain-to-gate-source charge ratio will allow designers
to incorporate less-expensive MOSFET drivers into end products, further
reducing component costs.
analogZONE Says . . .
There have been so many interesting power products in the last couple of months that I very nearly missed this one -- and that would have been a shame, for the little Si4362DY is a star that needs to be noticed. The gate-drain:gate-source charge ratio of 0.6 is remarkable and with the lowering of Rds(on) to 5.5 milliohms at 4.5 VGS and 4.5 milliohms at 10 VGS (both maximum) changes the way the dc-dc converter designer will have to think about his circuit designs. The complementary high-side Si4892DY also shows improvements over its predecessors but not in as striking a fashion as the low-side driver.
The Si4362DY is a TrenchFET with a maximum drain-source voltage of 30 V, and a maximum gate-source voltage of +/-12 V. The maximum steady-state drain current at 25 degrees C is 13 A, while the pulse drain current (10 us pulses) is 60 A. The total gate charge is a 42 nC typical and the gate resistance is a typical 1.3 ohms.
These parts will find ready acceptance in dc-dc converters and synchronous rectifiers by OEM designers and, lucky vendor that it is, FAEs from other semiconductor manufacturers will specify these products in tandem with their own company's ICs.
Both the Si4362DY and Si4892DY are in production in SO-8 and are priced
at $1.41 and $0.58, respectively, in 100-k-piece lots.