SLOS948 February 2019 TAS6424M-Q1
The bootstrap capacitors provide the gate-drive voltage of the upper N-channel FET. These capacitors must be sized appropriately for the system specification. A special condition can occur where the bootstrap may sag if the capacitor is not sized accordingly. The special condition is just below clipping where the PWM is slightly less than 100% duty cycle with sustained low-frequency signals. Changing the bootstrap capacitor value to 2.2 µF for driving subwoofers that require frequencies below 30 Hz may be necessary.