This paper presents a high-density DC-DC power delivery (PD) scheme using the proposed synergetic PD architecture (SyPoDA), enabling simultaneous 3-cell Li-ion battery charging under USB PD 3.2 protocol and single-inductor dual-output (SIDO) point-of-load (PoL) supplies. The proposed SyPoDA synergizes a switched-capacitor (SC) flash charger with our proposed hybrid SIDO converter, featuring 1) power stage sharing along charging and load-supply paths, 2) constant inductor DC current (I_L,DC) reduction at the PoL side, and 3) uninterrupted steady-state SIDO output current. It can improve the utilization of the high-voltage part power stage, reduce the inductor size, and lower the output capacitor (Co) requirement, improving the total power density. In circuit design, we propose a pulse-current-based gate driver (PCGD) circuit for monolithic GD integration. Fabricated in a 180-nm BCD process, the proposed SyPoDA prototype within a total 3D volume of 117mm³ achieves a 92.1% peak efficiency at 42 W total output when converting a 15-to-28-V input to three outputs of 12.6V/3.3V/1V. It supports a maximum output power of 80W.