ISL6568_06 Datasheet, PDF (27/29 Pages) Intersil Corporation – Two-Phase Buck PWM Controller with Integrated MOSFET Drivers for VRM9, VRM10, and AMD Hammer Applications

ISL6568
layers with vias should also be avoided, but if so, use two vias
for interconnection when possible.
Extra care should be given to the LGATE traces in particular
since keeping their impedance and inductance low helps to
significantly reduce the possibility of shoot-through. It is also
important to route each channels UGATE and PHASE traces
in as close proximity as possible to reduce their inductances.
Thermal Management
For maximum thermal performance in high current, high
switching frequency applications, connecting the thermal
GND pad of the ISL6566 to the ground plane with multiple
vias is recommended. This heat spreading allows the part to
achieve its full thermal potential. It is also recommended
that the controller be placed in a direct path of airflow if
possible to help thermally manage the part.
Suppressing MOSFET Gate Leakage
With VCC at ground potential, UGATE is high impedance. In
this state, any stray leakage has the potential to deliver
charge to the gate of the upper MOSFET. If UGATE receives
sufficient charge to bias the device on, a low impedance path
will be connected between the upper MOSFET drain and
PHASE. If this occurs and the input power supply is present
and active, the system could see potentially damaging
current. Worst-case leakage currents are on the order of
pico-amps; therefore, a 10kΩ 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.
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FN9187.4
March 9, 2006