Track and hold architecture with tunable bandwidth
First Claim
1. An apparatus comprising:
- a clock divider that receives a clock signal;
a plurality analog-to-digital converter (ADC) branches that each receive an analog input signal, wherein each ADC branch includes;
a delay circuit that is coupled to the clock divider;
an ADC having;
a bootstrap circuit that is coupled to the delay circuit;
a sampling switch that is coupled to the bootstrap circuit; and
a controller that is coupled to the bootstrap circuit to provide a control voltage to the bootstrap circuit so as to control a gate voltage of the sampling switch to adjust the impedance of the sampling switch when the sampling switch is actuated;
a sampling capacitor that is coupled to the sampling switch; and
an correction circuit that is coupled to the ADC; and
a mismatch estimation circuit that is coupled to each delay circuit, each correction circuit, and each controller, wherein the mismatch estimation circuit provides a control signal to each controller to adjust for relative bandwidth mismatches between the ADC branches.
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Abstract
To date, bandwidth mismatch within time-interleaved (TI) analog-to-digital converters (ADCs) has been largely ignored because compensation for bandwidth mismatch is performed by digital post-processing, namely finite impulse response filters. However, the lag from digital post-processing is prohibitive in high speed systems, indicating a need for blind mismatch compensation. Even with blind bandwidth mismatch estimation, though, adjustment of the filter characteristics of track-and-hold (T/H) circuits within the TI ADCs can be difficult. Here, a T/H circuit architecture is provided that uses variations of the gate voltage of a sampling switch (which varies the “on” resistance of the sampling switch) to change the bandwidth of the T/H circuits so as to precisely match the bandwidths.
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Citations
20 Claims
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1. An apparatus comprising:
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a clock divider that receives a clock signal; a plurality analog-to-digital converter (ADC) branches that each receive an analog input signal, wherein each ADC branch includes; a delay circuit that is coupled to the clock divider; an ADC having; a bootstrap circuit that is coupled to the delay circuit; a sampling switch that is coupled to the bootstrap circuit; and a controller that is coupled to the bootstrap circuit to provide a control voltage to the bootstrap circuit so as to control a gate voltage of the sampling switch to adjust the impedance of the sampling switch when the sampling switch is actuated; a sampling capacitor that is coupled to the sampling switch; and an correction circuit that is coupled to the ADC; and a mismatch estimation circuit that is coupled to each delay circuit, each correction circuit, and each controller, wherein the mismatch estimation circuit provides a control signal to each controller to adjust for relative bandwidth mismatches between the ADC branches. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An apparatus comprising:
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a clock divider that receives a clock signal; a plurality ADC branches that each receive an analog input signal, wherein each ADC branch includes; a delay circuit that is coupled to the clock divider; an ADC having; a bootstrap circuit that is coupled to the delay circuit; a sampling switch that is coupled to the bootstrap circuit; a controller that is coupled to the bootstrap circuit to provide a control voltage to the bootstrap circuit so as to control a gate voltage of the sampling switch to adjust the impedance of the sampling switch when the sampling switch is actuated; a sampling capacitor that is coupled to the sampling switch; an output circuit that is coupled to the sampling capacitor; and a sub-ADC that is coupled to the output circuit; and an correction circuit that is coupled to the ADC; a mismatch estimation circuit that is coupled to each delay circuit, each correction circuit, and each controller, wherein the mismatch estimation circuit provides a control signal to each controller to adjust for relative bandwidth mismatches between the ADC branches; and a multiplexer that is coupled to each ADC branch. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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16. An apparatus comprising:
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a clock divider that receives a clock signal; a plurality ADC branches that each receive an analog input signal, wherein each ADC branch includes; a delay circuit that is coupled to the clock divider; an ADC having; a bootstrap circuit that is coupled to the delay circuit; a PMOS transistor that is coupled to the bootstrap circuit; a controller that is coupled to the bootstrap circuit to provide a control voltage to the bootstrap circuit so as to control a gate voltage of the sampling switch to adjust the impedance of the sampling switch when the sampling switch is actuated; a sampling capacitor that is coupled to the PMOS transistor at its drain; an output circuit that is coupled to the sampling capacitor; and a sub-ADC that is coupled to the output circuit; and an correction circuit that is coupled to the ADC, wherein the correction circuit adjusts the output of its ADC to correct for DC offset and gain mismatch; a mismatch estimation circuit that is coupled to each delay circuit, each correction circuit, and each controller, wherein the mismatch estimation circuit provides a control signal to each controller to adjust for relative bandwidth mismatches between the ADC branches; and a multiplexer that is coupled to each ADC branch. - View Dependent Claims (17, 18, 19, 20)
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Specification