Automatic substrate switching circuit for on-chip adaptive power supply system

In energy-aggressive dynamic voltage scaling (DVS) techniques, adaptive on-chip power supply, which can provide variable voltage in a wide range, is highly demanded. However, potential leakage and latch-up problems arise, when substrate bias voltages of power transistors vary with the supply voltage. An automatic substrate switching circuit (ASSC) is presented in this paper to solve this problem, with the features of accurate voltage comparison, fast transient response and small on-chip area. HSPICE simulations show that the circuit automatically and accurately switches 1-nF PMOS transistor substrate voltage from 2.5 to 3.3 V within 60 ns. The comparison voltage range is from 1.2 V to 3.3 V. With TSMC 0.35 mum N-well CMOS process, the ASSC circuit only occupies 0.02 mm² silicon area with a static power of 116 muW