ANALOG TO DIGITAL CONVERTER WITH LEAKAGE CURRENT CORRECTION CIRCUIT
First Claim
1. In an analog to digital converter having a switched capacitor digital to analog converter, a reset switch, a dummy transistor having a shape factor substantially identical to that of the reset switch and a comparator, a method of cancelling a leakage current induced by the reset switch comprising steps of:
- (a) replicating a voltage appearing on an input sense node to the comparator onto a drain terminal on the dummy transistor to create a cancelling leakage current substantially similar to the leakage current induced by the reset switch; and
,(b) feeding back the cancelling leakage current to the input sense node of the comparator to cancel the leakage current.
1 Assignment
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Accused Products
Abstract
An analog to digital converter includes leakage current correction circuitry to cancel leakage current injected by a reset switch employing a dummy PMOS switch with a shape factor substantially similar to that of the reset switch. An operational amplifier replicates the voltage of the comparator sense input node to the drain of the dummy transistor to create the same operating point as the reset switch. The resulting leakage current is then repeated and fed back to the node to cancel the offending leakage current.
12 Citations
15 Claims
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1. In an analog to digital converter having a switched capacitor digital to analog converter, a reset switch, a dummy transistor having a shape factor substantially identical to that of the reset switch and a comparator, a method of cancelling a leakage current induced by the reset switch comprising steps of:
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(a) replicating a voltage appearing on an input sense node to the comparator onto a drain terminal on the dummy transistor to create a cancelling leakage current substantially similar to the leakage current induced by the reset switch; and
,(b) feeding back the cancelling leakage current to the input sense node of the comparator to cancel the leakage current. - View Dependent Claims (2, 3, 4, 5)
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6. In an analog to digital converter having a switched capacitor digital to analog converter, a reset switch and a comparator, a leakage current correction circuit comprising:
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a dummy transistor having a shape factor substantially identical to that of the reset switch; circuitry to replicate a voltage appearing on an input sense node to the comparator onto a drain terminal on the dummy transistor to create a cancelling leakage current substantially similar to the leakage current induced by the reset switch; and
,circuitry to feed back the cancelling leakage current to the input sense node of the comparator to cancel the leakage current.
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7. An analog to digital converter comprising:
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a switched capacitor digital to analog converter; at least one reset switch; a comparator, and, at least one leakage current correction circuit having a dummy transistor with a shape factor substantially identical to that of the at least one reset switch and circuitry to replicate a voltage appearing on an input sense node to the comparator onto a drain terminal on the dummy transistor to create a cancelling leakage current substantially similar to the leakage current induced by the reset switch and circuitry to feed back the cancelling leakage current to the input sense node of the comparator to cancel the leakage current. - View Dependent Claims (8, 9, 10, 11)
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12. A leakage current correction circuit comprising:
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an operational amplifier having an inverting input, a non-inverting input and an output; a first pMOS transistor having source, gate and drain terminals; a second pMOS transistor having source, gate and drain terminals, a first nMOS transistor having source, gate and drain terminals; a second nMOS transistor having source, gate and drain terminals, a third nMOS transistor having source, gate and drain terminals; a fourth nMOS transistor having source, gate and drain terminals;
whereinthe source and drain terminals of the first pMOS transistor are connected to a positive supply voltage; the drain terminal of the first pMOS transistor is connected to the source terminal of second pMOS transistor and to the inverting input of operational amplifier; the gate terminal of the second pMOS transistor is connected to the output of operational amplifier; the drain terminal of the second pMOS transistor is connected to the gate and the drain terminals of the first nMOS transistor and to the gate terminal of the second nMOS transistor; the source terminal of the second nMOS transistor is connected to the drain terminal of the fourth nMOS transistor; the non-inverting input of the operational amplifier is connected to the drain terminal of second nMOS transistor and to an input node on a comparator; the source terminal of the first nMOS transistor is connected to the gate and the drain terminals of the third nMOS transistor and to the gate terminal of the fourth nMOS transistor; the source terminal of the second nMOS transistor is connected to the drain terminal of the fourth nMOS transistor; and
,the source terminal of the third nMOS transistor and the fourth nMOS transistor are connected to a negative supply voltage. - View Dependent Claims (13, 14, 15)
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Specification