UCC21759-Q1 features the PWM interlock for IN+ and IN- pins, which can be used to prevent the phase leg shoot through issue. As shown in Table 7-1, the output is logic low while both IN+ and IN- are logic high. When only IN+ is used, IN- can be tied to GND. To utilize the PWM interlock function, the PWM signal of the other switch in the phase leg can be sent to the IN- pin. As shown in Figure 8-2, the PWM_T is the PWM signal to top side switch, the PWM_B is the PWM signal to bottom side switch. For the top side gate driver, the PWM_T signal is given to the IN+ pin, while the PWM_B signal is given to the IN- pin; for the bottom side gate driver, the PWM_B signal is given to the IN+ pin, while PWM_T signal is given to the IN- pin. When both PWM_T and PWM_B signals are high, the outputs of both gate drivers are logic low to prevent the shoot through condition.

Figure 8-2 PWM Interlock for a Half Bridge