Abstract: The backup mode of low-power MCU is usually supposed to have a flexible internal wakeup mechanism with extremely low power dissipation. In this work, we implement the no-voltage-regulator backup circuit through standard digital process by self-designed standard cells. Besides, the always-on module, PMU, is also optimized. The backup modules are implemented through backend process, and verified through simulations. The implemented circuits is proved to meet the design demand with a relatively ideal power dissipation.