Until recently, ASIC designers have mostly focused on how to achieve the desired performance requirements, and the typical ASIC design flow pays limited attention to power. In comparison, some custom designs have significantly advanced techniques for low power, such as voltage islands, substrate biasing, and sleep mode power gating. Butt custom designed chips can achieve low power at the same performance compared to ASIC chips designed in an EDA flow. In Closing the POWER Gap between ASIC & Custom, the significance of different low power design approaches is explored in detail. This book covers how to use low power design approaches in an automated design flow, and examine the design time and performance trade-offs of low power design. After chapter which outline factors affecting the power consumption of ASIC and custom designs and explore how each factor can contribute to custom designs being lower power than ASICs, the book focuses on the latest tools and techniques for low power design that may be applied in an ASIC design flow.