A mixed-mode voltage down converter with impedance adjustment circuitry for low-voltage high-frequency memories

This paper proposes a low voltage operation technique for a voltage down converter (VDC) using a mixed-mode VDC (MM-VDC), that combines an analog VDC and a digital VDC, and provides high frequency application using an impedance adjustment circuitry (IAC). The MM-VDC operates with a small response delay and a large supply current. Moreover, the IAC is adopted by the MM-VDC for wide range frequency operation under low voltage conditions. The IAC can change the supply current capability in accordance with the load operation frequency to avoid the overshoot and undershoot problems caused by the unmatched supply current. A 64 Mb-DRAM test device operated with the MM-VDC achieves well-controlled internal voltage (VCI) level and achieves high frequency operation. These systems, the MM-VDC and the IL-VDC, can be applicable for both low voltage and high frequency operation.