HIP4086, HIP4086A

13

FN4220.9

February 1, 2013

General PCB Layout Guidelines

The AC performance of the HIP4086/A depends significantly on

the design of the PC board. The following layout design

guidelines are recommended to achieve optimum performance:

• Place the driver as close as possible to the driven power FETs.

• Understand where the switching power currents flow. The high

amplitude di/dt currents of the driven power FET will induce

significant voltage transients on the associated traces.

• Keep power loops as short as possible by paralleling the

source and return traces.

• Use planes where practical; they are usually more effective

than parallel traces.

• Avoid paralleling high amplitude di/dt traces with low level

signal lines. High di/dt will induce currents and consequently,

noise voltages in the low level signal lines.

• When practical, minimize impedances in low level signal

circuits. The noise, magnetically induced on a 10kΩ resistor, is

10x larger than the noise on a 1kΩ resistor.

• Be aware of magnetic fields emanating from motors,

transformers and inductors. Gaps in these magnetic structures

are especially bad for emitting flux.

• If you must have traces close to magnetic devices, align the

traces so that they are parallel to the flux lines to minimize

coupling.

• The use of low inductance components such as chip resistors

and chip capacitors is highly recommended.

• Use decoupling capacitors to reduce the influence of parasitic

inductance in the VDD and GND leads. To be effective, these

caps must also have the shortest possible conduction paths. If

vias are used, connect several paralleled vias to reduce the

inductance of the vias.

• It may be necessary to add resistance to dampen resonating

parasitic circuits especially on xHO and xLO. If an external gate

resistor is unacceptable, then the layout must be improved to

minimize lead inductance.

• Keep high dv/dt nodes away from low level circuits. Guard

banding can be used to shunt away dv/dt injected currents

from sensitive circuits. This is especially true for control circuits

that source the input signals to the HIP4086/A.

• Avoid having a signal ground plane under a high amplitude

dv/dt circuit. This will inject di/dt currents into the signal

ground paths.

• Do power dissipation and voltage drop calculations of the

power traces. Many PCB/CAD programs have built in tools for

calculation of trace resistance.

• Large power components (Power FETs, Electrolytic caps, power

resistors, etc.) will have internal parasitic inductance which

cannot be eliminated. This must be accounted for in the PCB

layout and circuit design.

• If you simulate your circuits, consider including parasitic

components especially parasitic lead inductance.