Reference precharge system
AssigneeTexas Instruments Incorporated
InventorsAmit Kumar Gupta, Peng Cao
Life of this patent
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Abstract
A precharge circuit comprises a gain amplifier, a comparator, a reservoir capacitor, a switch, a current source, and a switching network. The gain amplifier has a gain G1 and receives an input voltage Vrefp. The gain amplifier outputs an amplified voltage G1Vrefp to the comparator, which compares G1Vrefp to a voltage across the reservoir capacitor. The comparator outputs a control signal for the switch based on the comparison. The switch couples the current source to the reservoir capacitor. The current from the current source charges the reservoir capacitor. The switching network couples the reservoir capacitor to an output of the precharge circuit during a first operating mode and provides the input voltage Vrefp to the output during a second operating mode.
Claims20
An apparatus, comprising:
- a gain amplifier coupled to a comparator and to a first voltage terminal;
- a reservoir capacitor comprising a first terminal and, a second terminal wherein the comparator is further coupled to the first terminal;
- a logic circuit coupled to the comparator and configured to generate a first control signal for a first switch and a second switch, wherein the first switch is configured to couple a current source to the first terminal of the reservoir capacitor, wherein the second switch is configured to couple a current sink to the second terminal of the reservoir capacitor;
- a common mode feedback (CMFB) loop coupled to the second terminal of the reservoir capacitor, the first terminal of the reservoir capacitor, and a common mode voltage terminal, the CMFB loop configured to generate a second control signal for the current sink;
- and
- a switching network configured to couple the first terminal of the reservoir capacitor to a first output and the second terminal of the reservoir capacitor to a second output based on a third control signal, and configured to couple the first voltage terminal to the first output and a second voltage terminal to the second output based on a fourth control signal.
A precharge circuit, comprising:
- a gain amplifier having a gain G1, the gain amplifier configured to receive an input voltage Vrefp and output an amplified voltage G1Vrefp;
- a comparator configured to compare the amplified voltage G1Vrefp and a voltage across a reservoir capacitor, and further configured to generate a control signal based on the comparison;
- a switch configured to couple a current source to the reservoir capacitor based on the control signal, wherein the current source is configured to generate a charging current for the reservoir capacitor;
- and
- a switching network configured to couple the reservoir capacitor to an output during a coarse charging portion of an integration operation performed by an analog to digital converter (ADC), wherein the output is configured to be coupled to a capacitor in the ADC, wherein the switching network is further configured to provide the input voltage Vrefp to the capacitor during a fine charging portion of the integration operation.
An apparatus, comprising:
- a first precharge circuit, comprising:
- a gain amplifier coupled to a first voltage terminal;
- a comparator coupled to the gain amplifier and to a first terminal of a capacitor, the comparator having an output for a first control signal, wherein a reservoir capacitor comprises the first terminal of the capacitor and a second terminal of the capacitor;
- a first switch configured to couple a current source to the first terminal of the capacitor based on the first control signal;
- a second switch configured to couple the first terminal of the capacitor to a first output during a first operating mode;
- a third switch configured to couple the first voltage terminal to the first output during a second operating mode;
- and
- a second precharge circuit, comprising:
- a feedback loop coupled to the first terminal of the capacitor, the second terminal of the capacitor, and to a second voltage terminal, the feedback loop configured to generate a second control signal for a current sink;
- a fourth switch configured to couple the current sink to the second terminal of the capacitor based on the first control signal;
- a fifth switch configured to couple the capacitor anode to a second output during the first operating mode;
- and
- a sixth switch configured to couple a third voltage terminal to the second output during the second operating mode.
Dependencies are inferred from the claim text.