An analog/digital (A/D) converting circuit is provided that stabilizes system operation, reduces power consumption in an analog circuit region and uses a selected metal-to-metal capacitor, which has a small parasitic capacitance value. The A/D converting circuit includes a first sample/hold amplifier for sampling/holding an analog input signal, a switch for selecting one of a signal outputted from the first sample/hold amplifier and a feedback signal and an A/D sub-converter for converting an analog signal outputted from the switch to a digital signal. A multiplying D/A converting block converts an output signal from the A/D sub-converter to an analog signal and amplifies a difference value obtained between the analog signal and the analog signal outputted from the switch. A second sample/hold amplifier samples/holds a signal outputted from the multiplying D/A converting block and outputs the feedback signal to the switch. A digital correcting unit outputs an N bit digital signal by superimposing output signals from the A/D sub-converter by 1 bit and a timing controller generates a control signal and a timing clock signal for the operation of each unit.
Methods and apparatus are provided for an analog converter. The apparatus comprises a first redundant signed digit (RSD) stage and a configurable block. The configurable block converts to a sample/hold circuit to sample a single ended analog signal. The sampled signal is then scaled, converted to a differential signal and provided to the first RSD stage. The first RSD stage outputs a bit value corresponding to the magnitude of the digital signal. In a next half clock cycle the first RSD stage calculates a residue that is provided to the configurable block. The configurable block is converted to a second redundant signed digit stage and generates a bit value corresponding to the magnitude of the residue provided by the first RSD stage. The first and second RSD stages cycle back and forth generating logic value each half clock cycle until the desired bit resolution is achieved. The configurable block is then converted back to a sample/hold circuit to start another conversion process.
A system and method for an improved analog front-end system is disclosed. By coupling a switch to the output of a track-and-hold circuit and to the input of a time-discrete circuit, such as an analog-to-digital converter, the time-discrete circuit can be disconnected from the track-and-hold circuit during the track mode of the track-and-hold circuit. This improved system reduces the load of the T/H circuit from the full input capacitance of the time-discrete circuit to the smaller parasitics of the switch thereby providing a T/H circuit with lower power consumption and smaller area while maintaining high speed and high accuracy. When the time-discrete circuit is an analog-to-digital converter, the system and method may also include a second shorted switch coupled between the first switch and the analog-to-digital converter for canceling the charge injection of the first switch and thereby enabling the analog-to-digital converter to convert an analog signal to a digital signal during the track phase of the track-and-hold circuit.
An analog to digital converter may achieve an output sampling rate that is not an integer multiple of the system clock. This may be done without using the conventional phase-locked loop circuit that generally requires a longer design time, more testing, and more silicon area. A pseudo clock may be generated from the system clock in which some of the system clock pulses are disabled to achieve a pseudo clock with the desired effective frequency.
Methods and circuit embodiments are disclosed for implementing an improved signal path for a sample-and-hold output. In exemplary embodiments, a sample-and-hold signal path for use in a pipelined ADC includes a sample-and-hold circuit configured to operate in two distinct phases. The sample-and-hold circuit includes an input node, an output node, and a power supply node. The power supply node is configured to power down the op amp during one phase and power up the op amp during the other phase. The sample-and-hold stage is configured to provide output during one phase only. Other aspects of the invention include embodiments in which a sample-and-hold stage signal path in a pipelined analog-to-digital converter is configured to accommodate a plurality of parallel outputs.
A sample hold circuit includes an op-amp, first capacitors provided on an inverting side of the op-amp and second capacitors provided on a non-inverting side. The sample hold circuit is configured such that a total capacitance of the first and second capacitors to which an input voltage is applied in a sampling phase is equal to that of the first and second capacitors to which the input voltage is applied in a holding phase, a total capacitance of the first capacitors to which the input voltage is applied in the holding phase is equal to that of the second capacitors to which the input voltage is applied in the holding phase, and a total capacitance of the first capacitors to which the input voltage is applied in the sampling phase is different from that of the second capacitors to which the input voltage is applied in the sampling phase.
