Low Power and High Efficiency Power Management Circuits Based on Flexible LTPO Technologies for Wearable Applications

In this paper, a Low-Temperature Polycrystalline Oxide (LTPO) Thin Film Transistors (TFTs) based power management integrated circuits (PMICs), consisting of both charge pump and low dropout regulator (LDO), are presented for the first time. A charge pump circuit is proposed to convert the supply voltage into both negative and doubled positive voltages with a minimum area overhead, which benefits from a switch-reused hybrid architecture and integration of both P and N type TFTs. A high performance LDO with a fixed-factor feedback network is proposed to reduce the output offset caused by the intrinsic process variation of flexible TFTs. The charge pump has an 8 V input, with outputs of +15.8 V and -7.8 V. With a load current range of 20 µA to 300 µA, the voltage drop across the charge pump remains below 1.2 V, with efficiency consistently exceeding 90% and peaking at 96.5%. The proposed LDO has a 4.53 V output, achieving an ultra-low quiescent current of 311 nA and delivering a load current of 11.6 mA.