During operation, the voltage on the OC/DT pin sets a maximum duration of the dead-time. If the adaptive dead-time has not triggered the turn-on of the internal MOSFET within this time, it switches on when the maximum dead-time expires. The relationship between the OC/DT pin voltage and this maximum programmable dead-time is shown in Figure 8-9 and given by Equation 3. The UCC25800-Q1 transformer driver also limits the maximum dead-time to be 1/8 of the switching cycle. Therefore, the programmed maximum dead-time is the lower value of these two.

Figure 8-9 Maximum dead time vs. OC/DT pin voltage

When the OC/DT pin voltage falls below 0.5 V, the transformer driver triggers the pin-short protection and it shuts down. When the OC/DT pin voltage is between 0.5 V to 3.95 V, the maximum dead-time is set by Equation 3 with a clamped maximum value of 1.35 μs and a clamped minimum value of 50 ns. When the OC/DT pin voltage is between 3.95 V and 4.5 V, it triggers the DT-out-of-range fault and the transformer driver shuts down. When the OC/DT pin voltage is above 4.5 V, the transformer driver shuts down due to the OC/DT open pin fault protection.