This paper presents a dual band Digitally-Controlled-Oscillator (DCO) based on Ring-Oscillators (RO) topology with differential input/output at 1.45 GHz is proposed. The circuit has two frequency band which switches by a digital mode bit. Switching between two bands of DCO, will change delay path and power consumption during the run time. A new Source-Coupled-Logic (SCL) based reconfigurable delay element with Schmitt-Trigger (ST) characteristic is used in each stage and 6 bits digital code control their current tails. Power consumption profile with frequency in each band has a steady regime. The proposed designs are fully differential, which is appropriate for low jitter high performance applications. The proposed DCO is simulated by spice with CMOS standard 0.18 mu m @ 1.8 v supply. The frequency, power consumption and jitter in lower band are 455.2 MHz to 505.1 MHz, 1.98 mW (at 455 MHz), 6.04 ps (at 505.1 MHz) and for upper band are from 1.39 MHz to 1.45 MHz, 9.7 mW (at 1.39 GHz) and 3.48 ps (at 1.45 MHz), sequentially. In this paper also circuit analysis of proposed DCO, delay calculation and comparison and analytical equation for frequency bands are obtained. Also, Monte Carlo and PVT test shows acceptable frequency tolerance.