High-precision open-loop tracking and holding circuit design for time-interleaved ADC - News - Global IC Trade Starts Here - megadownload

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0 Preface

With the development of digital communication systems, high-speed digital processing systems are increasingly demanding conversion between analog and digital signals. The two main developments of high-performance analog-to-digital converters (ADCs) today are high-speed, medium- and low-precision ADCs and low-speed, high-precision ADCs. The front-end T&H circuit is usually a key to the ADC design, and its dynamic accuracy directly affects the performance of the ADC.

1 open loop T&H circuit

In the design of ultra-high speed ADCs, a full parallel Flash structure or a time interleaving structure is generally used.

In the time interleaving structure, the front-end T&H circuit can adopt an open-loop or closed-loop structure according to design requirements. The closed-loop structure has a lower speed and higher precision, while the open-loop structure has a higher speed, but the accuracy itself is lower. The latter is used in this design.

The distortion of the T&H circuit is mainly derived from the nonlinear MOS switch resistance, the switching parasitic capacitance, and the switching charge injection. The nonlinearity of the on-resistance of the MOS switch in tracking the signal also limits the circuit tracking and settling time. Therefore, in ultra-high speed T&H circuits, the input sampling switch must have a low and nearly constant on-resistance.

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