SLLSFH8B August 2021 – February 2022 MCT8316A
The bulk capacitor should be placed to minimize the distance of the high-current path through the motor driver device. The connecting metal trace widths should be as wide as possible, and numerous vias should be used when connecting PCB layers. These practices minimize parasitic inductance and allow the bulk capacitor to deliver high current.
Small-value capacitors should be ceramic, and placed closely to device pins.
The high-current device outputs should use wide metal traces.
To reduce noise coupling and EMI interference from large transient currents into small-current signal paths, grounding should be partitioned between PGND and AGND. TI recommends connecting all non-power stage circuitry (including the thermal pad) to AGND to reduce parasitic effects and improve power dissipation from the device. Optionally, GND_BK can be split. Ensure grounds are connected through net-ties or wide resistors to reduce voltage offsets and maintain gate driver performance.
The device thermal pad should be soldered to the PCB top-layer ground plane. Multiple vias should be used to connect to a large bottom-layer ground plane. The use of large metal planes and multiple vias helps dissipate the I2 × RDS(on) heat that is generated in the device.
To improve thermal performance, maximize the ground area that is connected to the thermal pad ground across all possible layers of the PCB. Using thick copper pours can lower the junction-to-air thermal resistance and improve thermal dissipation from the die surface.
Separate the SW_BK and FB_BK traces with ground separation to reduce buck switching from coupling as noise into the buck outer feedback loop. Widen the FB_BK trace as much as possible to allow for faster load switching.