Embedded systems often use digital filtering after analog-to-digital conversion when signal conditioning is required. However, digital filters are computationally demanding, making them unsuitable for low-power microcontrollers. In this paper, we propose a fast and energy-efficient digital filtering technique based on look-up tables. The novelty in our technique is the use of multiple small LUTs, with a novel way to combine them to reduce the quantization error. As an additional novelty element, we propose a new input-centric efficient implementation, specific to LUT-based software filters. Experimental results confirm the technique's remarkable potential for speed as well as its energy efficiency.