Proper PCB layout is extremely important in a high-current fast-switching circuit to provide appropriate device operation and design robustness. The UCC27444-Q1 gate driver incorporates small propagation delays and powerful output stages capable of delivering large current peaks with very fast rise and fall times at the gate of power MOSFET to facilitate very quick voltage transitions. Very high di/dt causes unacceptable ringing if the trace lengths and impedances are not well controlled. The following circuit layout guidelines are recommended when designing with these high-speed drivers.

• Place the driver IC as close as possible to the power device in order to minimize the length of high-current traces between the driver IC output pins and the gate of the switching power device.
• Place the VDD bypass capacitors between VDD and GND as close as possible to the driver IC with minimal trace length to improve the noise filtering. These capacitors support high peak current being drawn from VDD pin, during turn-on of power MOSFET. The use of low inductance surface-mounted-device (SMD) components such as 50V rated X7R chip capacitors are highly recommended.
• The turn-on and turn-off current loop paths (driver device, power MOSFET and VDD bypass capacitor) must be minimized as much as possible in order to keep the stray inductance to a minimum. High dI/dt is established in these loops at two instances, namely during turn-on and turn-off transients, which induces significant voltage transients on the output pin of the driver device and Gate of the power MOSFET.
• Wherever possible, parallel the source and return traces to take advantage of flux cancellation.
• Separate power traces and signal traces, such as output and input signals.
• To minimize switch node transients and ringing, adding some gate resistance and/or snubbers on the power devices may be necessary. These measures may also reduce EMI.
• Star-point grounding is a good way to minimize noise coupling from one current loop to another. The GND of the driver is connected to the other circuit nodes such as source of power MOSFET and ground of PWM controller at one, single point. The connected paths must be as short as possible to reduce inductance and be as wide as possible to reduce resistance.
• Use a ground plane to provide noise shielding. Fast rise and fall times at OUT pin of the driver IC may corrupt the input signals of the driver IC. The ground plane must not be a conduction path for any high current (power stage) loop. Instead the ground plane must be connected to the star-point with one single trace to establish the ground potential. In addition to noise shielding, the ground plane can help in power dissipation as well
• External gate resistor and parallel diode-resistor combination may come in handy when replacing any gate driver IC with UCC27444-Q1 device in existing or new designs, specifically if they do not have the same drive strength.