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FN9075.7

July 25, 2005

Thermal Management

For maximum thermal performance in high current, high

switching frequency applications, connecting the thermal

pad of the QFN part to the power ground with a via, or

placing a low noise copper plane underneath the SOIC part

is recommended. This heat spreading allows the part to

achieve its full thermal potential.

Suppressing MOSFET Gate Leakage

With VCC at ground potential, UGATE and LGATE are high

impedance. In this state, any stray leakage has the potential

to deliver charge to either gate. If UGATE receives sufficient

charge to bias the device on (Note: Internal circuitry prevents

leakage currents from charging above 1.8V), a low

impedance path will be connected between the MOSFET

drain and PHASE. If the input power supply is present and

active, the system could see potentially damaging currents.

Worst-case leakage currents are on the order of pico-amps;

therefore, a 10k

Ω resistor, connected from UGATE to

PHASE, is more than sufficient to bleed off any stray leakage

current. This resistor will not affect the normal performance

of the driver or reduce its efficiency.

ISL6207