This paper presents a model of the hybrid LLC converter, emphasizing on deadtime interval dynamics that become too impactful to ignore for preserving model accuracy at MHz-level operation. The time-domain modeling approach is adopted and a new parameter kC, defined as the capacitance ratio between the resonant capacitance Cr and switch output capacitance Coss, is introduced to model the state variables during the transition intervals. The proposed model, validated by PSIM circuit simulation, is used to derive ZVS constraints of the topology, especially for the less frequently addressed upper deadtime limit to prevent an eventual Coss recharge, due to an early resonant current reversal. The ZVS limits proposed are validated on a 500W, 400V/18-36V GaN-based experimental prototype at 500kHz.