A metastable state detection device and method, and an ADC circuit are disclosed. The metastable state detection device includes: a delay unit which is configured to receive a synchronization signal and delay the synchronization signal based on preset step delay values; a first flip-flop unit including a first clock input terminal, a first data input terminal and a first data output terminal, wherein the first clock input terminal is configured to receive a clock signal; the first data input terminal is configured to receive the delayed synchronization signal; a second flip-flop unit including a second clock input terminal, a second data input terminal and a second data output terminal; a processing module connected to the second data output terminal, which is configured to receive a target clock signal and detect a metastable state of the first flip-flop unit according to the target clock signal.

The present disclosure provides a buffer circuit and a buffer. The buffer circuit includes: an input follower circuit for following the voltage change of the first input signal; an input follower linearity boosting circuit for improving follower linearity of the input follower circuit; a first voltage bootstrap circuit for bootstrapping the voltage of the first input signal; a second voltage bootstrap circuit for bootstrapping the voltage of the second input signal; a third voltage bootstrap circuit for providing corresponding quiescent operation point voltage; a compensation follower circuit for following the compensation voltage; a compensation follower linearity boosting circuit for improving follower linearity of the compensation follower circuit; a first load for collecting the buffered voltage; a bias circuit for providing a bias current for the buffer; a bias linearity boosting circuit for improving linearity of the bias circuit; a second load for generating a nonlinear compensation current.

In one embodiment, a waveform generating device includes a first DA converter converting input data, a controller outputting a first signal having a command value based on the input data, and a second signal having a command value differing by a constant value from the first signal, a second DA converter converting the first signal, a third DA converter converting the second signal, and a combiner combining the output of the first DA converter, the output of the second DA converter, and the output of the third DA converter. When a value of a predetermined first high-order bit of the input data is inverted, the controller changes the command value of the first signal such that a value of the first high-order bit or a second high-order bit different from the first high-order bit is inverted.

A control circuit for a successive approximation register analog-to-digital converter (SAR ADC). The SAR ADC includes a comparator and a switched-capacitor digital-to-analog converter (DAC). The switched-capacitor DAC includes a target capacitor. A first terminal of the target capacitor is coupled to an input terminal of the comparator. A second terminal of the target capacitor is coupled to a first reference voltage through a first switch and coupled to a second reference voltage through a second switch. The control circuit includes a third switch and a buffer circuit. The third switch is coupled between the first reference voltage and the second terminal of the target capacitor. The buffer circuit is coupled to the first switch and the third switch for controlling the first switch and the third switch based on a control signal.

Digital to analog converter generates an analog output corresponding to a digital input by controlling DAC cells using bits of the digital input. The DAC cells individually make a contribution to the analog output. Due to process, voltage, and temperature variations, the DAC cells may have duty cycle error or mismatches. To compensate for the duty cycle error of a DAC cell, a small amount of charge is injected into a low-impedance node of a DAC cell when the data signal driving the DAC cell transitions, or changes state. The small amount of charge is generated using a capacitive T-network, and the polarity of the charge injected is opposite of the error charge caused by duty cycle error. The opposite amount of charge thus compensates or cancels out the duty cycle error, and duty cycle error present at the output of the DAC cell is reduced.

A metastable state detection device and method, and an ADC circuit are disclosed. The metastable state detection device includes: a delay unit which is configured to receive a synchronization signal and delay the synchronization signal based on preset step delay values; a first flip-flop unit including a first clock input terminal, a first data input terminal and a first data output terminal, wherein the first clock input terminal is configured to receive a clock signal; the first data input terminal is configured to receive the delayed synchronization signal; a second flip-flop unit including a second clock input terminal, a second data input terminal and a second data output terminal; a processing module connected to the second data output terminal, which is configured to receive a target clock signal and detect a metastable state of the first flip-flop unit according to the target clock signal.

Certain aspects of the present disclosure are directed to a radio frequency digital-to-analog converter (RFDAC). The RFDAC generally includes a plurality of digital-to-analog (DAC) unit cells. At least one DAC unit cell is capable of being configured in an active state or in a sleep state. For the at least one DAC unit cell, an output impedance of the DAC unit cell in the active state is equal to an output impedance of the DAC unit cell in the sleep state.

Systems and methods for an asynchronous successive approximation register analog-to-digital converter (SAR ADC) with word completion algorithm may include a SAR ADC comprising a plurality of switched capacitors, a comparator, a metastability detector including a timer having a tunable time interval, and a successive approximation register. The SAR ADC may sample input signals at inputs of the switched capacitors; compare signals at outputs of the switched capacitors, each for a respective bit; sense whether a metastability condition exists for the comparator using the timer and setting a metastability flag upon each metastability detection for each bit; increase a value of the tunable time interval if more than one metastability flag is set during conversion of a sampled input signal; decrease a value of the tunable time interval if no metastability flags are set; and use the flags for a word completion in the cases when not all the bits have been evaluated.

A control circuit for a successive approximation register analog-to-digital converter (SAR ADC). The SAR ADC includes a comparator and a switched-capacitor digital-to-analog converter (DAC). The switched-capacitor DAC includes a target capacitor. A first terminal of the target capacitor is coupled to an input terminal of the comparator. A second terminal of the target capacitor is coupled to a first reference voltage through a first switch and coupled to a second reference voltage through a second switch. The control circuit includes a third switch and a buffer circuit. The third switch is coupled between the first reference voltage and the second terminal of the target capacitor. The buffer circuit is coupled to the first switch and the third switch for controlling the first switch and the third switch based on a control signal.

The present disclosure provides a buffer circuit and a buffer. The buffer circuit includes: an input follower circuit for following the voltage change of the first input signal; an input follower linearity boosting circuit for improving follower linearity of the input follower circuit; a first voltage bootstrap circuit for bootstrapping the voltage of the first input signal; a second voltage bootstrap circuit for bootstrapping the voltage of the second input signal; a third voltage bootstrap circuit for providing corresponding quiescent operation point voltage; a compensation follower circuit for following the compensation voltage; a compensation follower linearity boosting circuit for improving follower linearity of the compensation follower circuit; a first load for collecting the buffered voltage; a bias circuit for providing a bias current for the buffer; a bias linearity boosting circuit for improving linearity of the bias circuit; a second load for generating a nonlinear compensation current.