A Quasi-Digital Ultra-Fast Capacitor-Less Low-Dropout Regulator Based on Comparator Control for x8 Current Spike of PCRAM Systems

Abstract

This paper presents a comparator-based Quasi-Digital LDO (QDLDO) for the negative supply which has an ultra-fast transient response for the PCRAM systems. Even under the sharp spike of a load current having a peak value of 80 mA with a short rising time of 2.5 ns, the QDLDO effectively minimized a voltage spike on the output voltage, reducing it to 150 mV within only 40 ns. With I/O transistors to withstand I/O voltage stress, this LDO achieved the best FOM of 0.042 V/um(2), among the other state-of-the-art LDOs fabricated in more advanced technologies.