Nowadays multi-functional wearable devices generally require high current drive capability because microcontrollers (MCU) or rechargeable batteries are embedded inside. To achieve both high current and high power efficiency, this article presents a switched-inductor-based AC-DC buck converter that is implemented on a 0.18 µm chip manufacturing process for transcutaneously powered wearable devices. Different from multi-stage AC-DC converters that were widely used for wearable devices, the presented single-stage circuit has concise structure but provides flexible voltage output, high efficiency, and high current drive capability. The maximum output current can go up to 250 mA, and the peak efficiency is measured as 80.1% for 100 mA load current. The chip size is 185 µm × 260 µm.

Low-drop-out (LDO) voltage regulators have been widely used in the power supply of the integrated circuits (ICs). With the evolution of the IC manufacturing process and its applications, the design of the analog controlled LDO has encountered more challenges in recent years. This paper starts with the discussion of low supply voltage and low output capacitor problems that have been found in the analog controlled LDO. To solve the mentioned problems, a novel design concept of the digitally controlled LDO is then presented. To verify the feasibility of the real implementation, the designed circuit is validated using the NanoSim/VCS software in a 0.18 μm manufacturing process before the circuit is taped-out. With the test condition of 1 V supply voltage, the stability of the proposed LDO is guaranteed when a small output capacitor (1 μF) with very low equivalent series resistance (1 mΩ) is used. Load test result shows that the output voltage spike is only 40 mV with 3 μs recovery time when the load current steps-up from 1 to 51 mA.