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The overall success in the low voltage MOSFET
market depends primarily on how closely semiconductor
suppliers match the expectations of the electronic
industry. The improvement in low voltage MOSFET
technology continues at a rapid pace as devices
with new geometries or greater densities continue
to be introduced.
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The advantages which come from the built-up cell density and scaled-down features are traceable in the lowest on-resistance in the market. |
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ST has just developed a new generation of the well known STripFET technology: STripFET III. This process is also known as EHD3 (Extremely High Density) resulting from the enhanced density of the equivalent cells, well above 57 Mcells/inch².
EHD3’s main feature is the strip width and the inter-strip gaps, which bring a considerable channel perimeter density: W=62m/cm²
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High cell density and channel perimeter
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Extremely low figure of merit
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Optimized intrinsic recovery |
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Figure of merit
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Specific RDS(on) |
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From "NF" to "NH" STripFET
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Relative Efficiency at 500kHz
Single Phase VIN=12V VOUT=2V
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Buck Converter |
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Evaluation Circuit for Efficiency
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The EHD3, thanks to the decreased strip width, gains 38% in the channel perimeter per unit area, with respect to the second generation, this also means a great benefit in terms of RDS(on)
The figure of merit (RDS(on) *Qg) has been slashed by 43%. The following graph explains the trend in this parameter, which is of paramount importance in many applications.
On account of the main power supply requirement to operate at the highest efficiency, special attention has been given to the reverse recovery characteristic of the parasitic body diode.
In particular the Qrr is 39% smaller than in the previous EHD generations. Moreover, the low intrinsic resistance, Rg (<1.9ohm) is of outstanding importance to reduce the gate driving power losses. All these improvements are useful attributes in applications, especially for synchronous rectification for motherboard market, that allow us to consider the EHD3 technology as a benchmark in the low voltage scenario.
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Synchronous buck converter for computer and telecom applications.
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The effective improvement in the technology has been combined with new packages and new bonding techniques. The bondless SO-8 and PowerSO-8 are the most attractive solutions with a standard pin-out configuration of SO-8. The new ClipPAK has the same clip concept already adopted in the SO-8 package, but without any external difference from a standard DPAK. EHD3 in PowerFLAT and in PowerSO-8 with clip mounting will be available shortly.
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Vertical sections of two EHD generations, showing the decreased strip width and a consequent strip density increase of nearly 40% in the third generation
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