Ultra-low power SRAM is a promising memory for the next-generation electronics that focus on green and power-aware computing. Unfortunately, ultra-low power SRAM encounters serious timing uncertainty. One of the major problems is that the conventional voltage-clamping circuits cannot work when the bitlines have serious with-in-die variations. The full swing, usually required on the bitline, causes unwanted power dispassion. Therefore, this work proposes a novel SRAM cell that can clamp the bitline voltage autonomously. This voltage clamping is also independent in each bitline and is adapted automatically under dynamic voltage scaling. The dynamic power on bitline discharge can be saved by 75% by using the proposed structure, with an acceptable overhead in access time.