Texas Instruments Corporation

Sabu Paul

Raghu Nandan Srinivasa

Srinivas Bangalore Seshadri

Saugata Dutta

A reference voltage generator comprises a comparator, a digital-to-analog converter (DAC) and a switched capacitor accumulator. The comparator receives a reference voltage input, a feedback input, and a control signal. The DAC is coupled to an output of the comparator, and the switched capacitor accumulator is coupled to an output of the DAC. In some implementations, a digital filter is coupled between the output of the comparator and the input of the DAC. The switched capacitor accumulator can be coupled to a buffer that outputs the feedback input and a reference voltage for an analog-to-digital converter (ADC). In some implementations, the feedback loop includes N one-bit DACs coupled to the output of the comparator and N switched capacitor accumulators, each of which is coupled to a unique one-bit DAC.

Reference buffer

A pipelined analog-to-digital converter (ADC) and a residue amplifier used in the ADC. An ADC includes a capacitive digital-to-analog converter (CDAC), a residue amplifier, and a switched capacitor circuit. The residue amplifier is coupled to the CDAC. The residue amplifier includes a first complementary transistor pair and a first tail current circuit. The first complementary transistor pair is coupled to a first output of the CDAC, and includes a high-side transistor and a low-side transistor. The first tail current circuit is coupled to the high side transistor. The switched capacitor circuit is coupled to inputs of the CDAC and to the first tail current circuit. The switched capacitor circuit is configured to generate a voltage to bias the first tail current circuit with compensation for common mode voltage at the inputs of the CDAC.

Residue amplifier

A successive approximation register analog-to-digital converter with improved kick-back linearization includes a signal input terminal, a capacitive digital-to-analog converter, a first switch, and a second switch. The signal input terminal is configured to receive a signal to be digitized. The capacitive digital-to-analog converter includes a first capacitor array, a second capacitor array, and a coupling capacitor. The first capacitor array includes a plurality of capacitors. The second capacitor array includes a plurality of capacitors. The coupling capacitor connects the first capacitor array to the second capacitor array. The first switch is configured to switchably connect a bottom plate of each of the capacitors of the first capacitor array to the signal input terminal. The second switch is configured to conduct a voltage on the bottom plate of the coupling capacitor to the signal input terminal.

Successive approximation register analog-to-digital converter with kickback linearization

One example includes a pipelined analog-to-digital converter device. The pipelined analog-to-digital converter device includes a capacitive digital-to-analog converter, a first analog-to-digital converter, and a second analog-to-digital converter. The capacitive digital-to-analog converter includes a capacitor comprised of a top plate and a bottom plate, the capacitive digital-to-analog converter sampling an analog input signal applied to the pipelined analog-to-digital converter device while the capacitor is grounded, holding the sampled analog input while the top plate is floated, and outputting a residue voltage. The second analog-to-digital converter is coupled to the top plate of the capacitor, the second analog-to-digital converter producing a second digital representation of voltage on the top plate of the capacitor after the top plate is floated, wherein the second digital representation represents fine bits produced by the first stage of the pipelined analog-to-digital converter device.

Analog-to-digital converter with an increased resolution first stage

A circuit for equalizing the impedances of a PMOS device with an NMOS device includes a first reference voltage coupled to the source of the first PMOS device. A second reference voltage is coupled to the source of the NMOS device. A first node has a common mode voltage between the first reference voltage and the second reference voltage. A second node is located between the PMOS device and the NMOS device. A first gate voltage is coupled to the gate of either the PMOS device or the NMOS device. An operational amplifier has a first input coupled to the first node and a second input coupled to the second node, the output of the operational amplifier is a second gate voltage that is coupled to the gate of one of either the PMOS device or the NMOS device that is not coupled to the first gate voltage.

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Sabu Paul