Current switch driver and current source designs for high-speed current-steering DAC

Based on analyzing of the influence of the current switch driver on dynamic performance of the high-speed current-steering DAC, several key points of designing the current switch driver are proposed. The low cross-point method, synchronous flip-latch and limited swing of switch driver are introduced, and a current switch driver circuit is proposed. In order to further improve the dynamic performance of the DAC, this paper presents a high output impedance current source circuit. A gain stage is utilized in the biasing circuit of the current source, and the output impedance of the proposed current reaches 10⁸ Omega, which is important to fulfill the performance requirements of the DAC. A 14-bit high-speed DAC is designed using the currentswitch driver and current source under a 0.35 mum CMOS process. When the frequency of the full-range input signal is 24.6 MHZ and the sample frequency is 140 MSPS, the SFDR of the DAC achieves 78.2 dB.And the settling time is about 10 ns.