Buffered bootstrapped input switch with cancelled charge sharing for use in high performance sample and hold switched capacitor circuits
AssigneeTexas Instruments Incorporated
InventorMaher M. Sarraj
Life of this patent
Estimating the term…
Abstract
A buffered bootstrapped input switch employs cancelled charge sharing for use in high performance sample and hold switched capacitor circuits especially useful for implementing, for example, an analog-to-digital converter (ADC) or amplifier circuit front end sampling network, among others. A scheme is employed for estimating the charge loss from the bootstrapping capacitor to the gate of the bootstrapped input switch, storing the estimated charge loss on a small capacitor, buffering the small capacitor, and then adding the estimated charge loss in series to the bootstrap capacitor, to provide an almost ideal bootstrap network.
Claims7
A switching network comprising:
- at least one MOS switch having a gate and a source;
- a bootstrapping capacitor configured to maintain a substantially constant voltage between the gate and the source of the at least one MOS switch;
- and
- a dummy input network configured to eliminate charge sharing between the bootstrapping capacitor and the gate capacitance of the at least one bootstrapped MOS switch, said dummy input network including a second capacitor, said dummy input network estimating the charge loss from the bootstrapping capacitor to the gate of the MOS switch, storing the estimated charge loss on a second capacitor, and adding the stored charge loss to the charge loss from the bootstrapping capacitor such that the voltage across the gate and source of the MOS switch is a full supply voltage.
A method of canceling charge sharing comprising the steps of:
- providing a switching network comprising at least one bootstrapped input switch and a dummy input network configured to constantly measure charge loss associated with the at least one bootstrapped input switch;
- and
- canceling charge sharing between the at least one bootstrapped input switch and a bootstrapping capacitor in response to the measured charge loss;
- wherein the step of canceling charge sharing between the at least one bootstrapped input switch and a bootstrapping capacitor in response to the measured charge loss comprises the steps of:
- estimating the charge loss from the bootstrapping capacitor to the gate of the MOS switch;
- storing the estimated charge loss on a second capacitor, and
- adding the stored charge loss to the charge loss from the bootstrapping capacitor such that the voltage across the gate and source of the MOS switch is at least a full supply voltage.
Dependencies are inferred from the claim text.