This paper proposes a fully integrated 32-MHz relaxation oscillator (ROSC)
capable of fast start-up time operation for low-power intermittent VLSI
systems. The proposed ROSC employs current mode architecture that is
different from conventional voltage mode architecture. This enables compact
and fast switching speed to be achieved. By designing transistor sizes
equally between one in a bias circuit and another in a voltage to current
converter, the effect of process variation can be minimized. A prototype
chip in a 0.18-um CMOS demonstrated that the ROSC generates a stable
clock frequency of 32.6 MHz within 1-us start-up time. Measured line
regulation and temperature coefficient were ±0.69% and ±0.38%,
respectively.