| This dissertation presents a low-quiescent-current dual-mode digitally-controlled buck converter IC for cellular phone applications. In cellular phones, the load current demanded by the on-board circuitry varies from below 0.1 mA up to a few hundred mA, reflecting operation in standby and active (talk) modes. Thus, high efficiency over a wide load range is of high priority for power management units, since the total energy is limited by the capacity of a single cell Li-ion battery. A dual-mode buck converter IC, implemented with a 0.25-mum CMOS process, takes 2 mm2 active area and demonstrates equal or better regulation performance compared to state-of-the-art analog switchers. A very low quiescent current of 4 muA is achieved experimentally, resulting in a more than three-fold reduction compared to the leading state-of-the-art analog controllers. Consequently, a high efficiency, exceeding 70%, is achieved over a wide load range between 0.1 and 400 mA. |
