Feedforward spectral shaping technique for clock-jitter induced errors in digital-to-analogue converters

A simple feedforward spectral shaping technique for the pulsewidth jitter induced errors in digital-to-analogue converters (DACs) is presented. The proposed technique features a feedforward combination of the conventional rectangular-pulse switched-current DAC and a discrete-time switched-capacitor DAC to achieve spectral shaping for the jitter induced error. The benefit of this hybrid DAC solution using error specral shaping is illustrated in the context of feedback DACs used in continuous-time ΔΔ modulators. Simulation results show that the jitter tolerance of the proposed DAC solution is equivalent to that of the commonly used jitter-tolerant exponentially-decaying waveform switched-capacitor-resistor DAC structure, but at much more relaxed slew-rate requirement on the op-amp used in the DAC load circuit, which translates into significant power savings.