DirectFET® MOSFET: EMC Considerations
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EMC Test Set Up
- Silicon from same wafer lot assembled into SO-8, MLP, D-PAK, D2PAK & DirectFET®
- Devices assembled onto circuit board containing gate drive oscillator, gate driver and 1 Ohm high side load
- All circuits identical except for land pad design and power package present
- Circuit switching at 1MHz
- Circuits tested for radiated emission in anechoic test chamber
- Limits: EN55022:1994 Class B
- Antenna placed at 1m from circuit*
* NB. Standard is 3m
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EMC Test Results
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EM signal from circuit containing DirectFET packaged silicon
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EM signal from circuit containing D-PAK packaged silicon
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FREQUENCY RANGE 30MHz – 1000MHz
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Conclusions
- All packages characterised show an increase in resistance with frequency above 1MHz due to skin effect related phenomenon
- DirectFET has lowest resistance and inductance at high frequency compared to wirebonded MLP, SO-8, D2PAK and D-PAK packages
- Wider implications: Multi-chip D2PAK based technologies will not be efficient above 1MHz + due to lead inductance
- In existing circuits, substituting the DirectFET MOSFET for earlier packages, such as D2Pak, D-Pak, MLP, or SO-8 will not
increase the EMI. This demonstrates that replacing a plastic package with a DirectFET metal can does not degrade the overall EMI.
- Replacing an existing circuit with a smaller layout, made possible by the DirectFET MOSFET, will actually improve (lower) the EMI generated
by the circuit due to the lower overall inductance of the new solution.
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No significant difference in peak EM signal measured between circuits containing DirectFET® and other packages
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EMI Test for Class D Audio Amplifier application
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TO-220
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DirectFET MOSFET
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Test Results
- Results show that both amplifiers with DirectFET and TO-220 meet audio amplifier conducted EMI standards limits (CISPR13).
- Even if rise and fall times in DirectFET amplifier are approximately three times faster than TO-220 amplifier, results show better conducted EMI performance when the DirectFET is used.
- The test conditions are:
- 1/8 POUT (12.5W) & 1KHz sinusoidal input signal
- Over 2MHz, DirectFET amplifier shows approximately 9dBuV lower Peak, Quasi-Peak and Average noise than TO-220 amplifier.
- Because test room is not shielded, background noise is not low enough. However, DirectFET and TO-220 amplifiers were tested under same background conditions.
IR’s proprietary DirectFET® technology is covered by US Patent 6,624,522 and
other US and foreign pending patent applications.
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