Envelope tracking (ET) and average power tracking (APT) have been widely used as supply modulators of power amplifiers (PAs). To meet the new challenges brought by the 5G NR standard, the symbol power tracking (SPT) technique is proposed, which is more efficient than ET and more flexible than APT. For the application of subcarrier spacing (SCS) of 15-60kHz in the frequency range 1 (FR1), this paper proposed a buck-boost SPT supply modulator with a transition time below 1.17- μs for 5G NR PA in the smartphone. The combination of three techniques improves the voltage transition speed. The charge-pump-based switching power modulator increases the output voltage higher than the battery voltage and offers a high voltage source for the auxiliary current paths (ACP). The ACP introduces additional currents to charge/discharge the 1- μF output capacitor. The end-point-prediction (EPP) scheme lets the compensator convert directly from one steady state to the next. This supply modulator circuit is designed and fabricated using 0.18- μm BCD technology. The output voltage range is 1-5-V. The maximum transition speed can be up to 0.37- μs/V and 0.15- μs/V for up-tracking and down-tracking, respectively.