Bootstrapping circuit with IGZO TFTs for on-chip power supply generation

This paper reports a novel bootstrapping circuit with IGZO TFTs to generate on-chip power supply, mainly for real-time flexible wearable continuous health monitoring system. In order to ensure a compact and reliable system without complex external connections, on-chip power supply is required, to drive biological signal processing or conditioning circuits with IGZO TFTs. Though, integrated system (circuits with oxide TFTs and thin film batteries) can be achieved with printing technique, with the state of art, commercially available thin film printed batteries are confined to 3 V. Typically, flexible electronics with IGZO TFTs needs a power supply > 5 V (depending on the dielectric). The proposed bootstrapping (BS) circuit with IGZO TFTs can generate 2*VDD and 3*VDD with the printed batteries output voltage of around 3 V. The proposed circuit is tested with an input voltage spanning between 2 to 10 V and clock frequency up to 1 MHz. When the input voltage is 3 V with the load of 5 MO and 2 MO, the output which is acquired is 7.9 V and 6.4 V, respectively, with the respective power dissipation of 24.9 µW and 50.8 µW. The circuit simulations are carried out using IGZO TFT model in cadence virtuoso environment, which demonstrate that the BS circuit plays a vital role in the on-chip supply generation for wearable biomedical systems.