This paper presents an all-digital signal component separator (SCS) with low power overhead for uneven multilevel LINC (UMLINC) systems, including a multi-level phase calculator (MLPC) and a digitally-control phase shifter (DCPS) pair. The optimal gain level with branch mismatch consideration is proposed to achieve maximal average efficiency 44.82%. This SCS chip is manufactured in 90 nm standard CMOS process with an active area 0.5 mm2. The required phases of branch signals and PA gain controls can be calculated by the proposed MLPC. Instead of four DACs, the DCPS pair with a continuous PVT monitor is also proposed to generate the phase-modulated signals accurately at IF frequency 80 MHz with 8-bit resolution. By applying voltage scaling and source gating on DSP functions and DCPSs respectively, 81.32% power cost of SCS can be reduced, and the overall power is only 0.65 mW. With the proposed SCS, the EVM of -31.06 dB using 64-QAM OFDM signals can be achieved for high-efficiency UMLINC systems.