A 0.07-mm2 162-mW DAC Achieving >65 dBc SFDR and <-70 dBc IM3 at 10 GS/s With Output Impedance Compensation and Concentric Parallelogram Routing

A digital-to-analog converter (DAC) with small-size non-cascoded current cells is proposed to achieve small area, low-power consumption, and high linearity over a wide bandwidth. An output impedance compensation (OIC) technique using a compensation resistor, implemented by a PMOS with code-dependent gate voltage control, is proposed to remedy the nonlinearity induced by the insufficient output impedance of the non-cascoded current cells. In addition, a proposed concentric parallelogram routing (CPR) technique, in which the subcells of each current cell are arranged such that they form a parallelogram shape with a common centroid, is used to reduce both the mismatch error and the routing-induced timing skew among the current cells. The DAC, implemented in a 28-nm CMOS process, achieves >65-dBc spurious-free dynamic range (SFDR) and < -70-dBc third-order intermodulation distortion (IM3) over the entire Nyquist bandwidth at 10 GS/s while consuming 162 mW from a single 1.1 V supply.