||The thesis is composed of two topics : a charger circuit of Li-ion batteries for wireless biomedical systems and a capacitor-less low dropout regulator（LDO）. |
The first topic discloses a charger circuit of Li-ion batteries using 2P4M 0.35-μm CMOS process, which comprises a small bias circuit, a comparator with hysteresis, a transistor voltage divider circuit, a power MOS, and a Li-ion charger with a cut-off voltage and a recharge voltage. The proposed design receives a 13.56 MHz carrier with 5±0.2 V amplitude to charge the Li-ion batteries with a small constant current.
The second topic reveals a low dropout regulator （LDO） without capacitor load and ESR, including a bias circuit, an error amplifier, and a Flipped Voltage Follower circuit generating a stable output voltage independent on different loads. The proposed design improves the input voltage limitation of Flipped Voltage Follower by compensating phase margin such that the proposed design shows a good transient response and stability without any output capacitor. The proposed LDO is implemented by 1P6M 0.18-um CMOS process, which can operate correctly given an input voltage range from 3.3~4.2 V.