Optimum performance of gate drivers cannot be achieved without taking due considerations during circuit board layout. The following points are emphasized:
- Low ESR/ESL capacitors must be connected close to the IC between VDD and GND pins to support high peak currents drawn from VDD during the turn-on of the external MOSFETs.
- Grounding considerations:
- The first priority in designing grounding connections is to confine the high peak currents that charge and discharge the MOSFET gates to a minimal physical area. This will decrease the loop inductance and minimize noise issues on the gate terminals of the MOSFETs. The gate driver should be placed as close as possible to the MOSFETs.
- 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.
- Use a ground plane to provide noise shielding. Fast rise and fall times at OUT may corrupt the input signals during transition. The ground plane must not be a conduction path for any current 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.
- In noisy environments, tying inputs of an unused channel of the UCC2742x device to VDD or GND using short traces in order to ensure that the output is enabled and to prevent noise from causing malfunction in the output may be necessary.
- Separate power traces and signal traces, such as output and input signals.