Dynamically boosted current source circuit
First Claim
1. A dynamically boosted current source circuit, comprising:
- an input node, a threshold detector arranged to detect when an input signal connected to said input node crosses a first predetermined threshold, a capacitive node connected such that the speed with which said capacitive node changes state affects the response speed of an associated circuit that is responsive to a transition of said input signal, a boosted node connected such that the current received at said boosted node affects the speed with which said capacitive node changes state, and a current source arranged to provide a first current to said boosted node when said input signal is idle and a boosted current greater than said first current to said boosted node when said threshold detector detects that said input signal has crossed said first predetermined threshold, said current source arranged such that the rate at which its output current is slewed from said first current to said boosted current and the amplitude of said boosted current are independent of the slew rate and amplitude of said input signal, said boosted current increasing the speed with which said capacitive node changes state and there by the speed with which said associated circuit responds to a transition of said input signal.
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Abstract
A dynamically boosted current source circuit improves the response speed of a circuit responsive to a transitioning input signal. The circuit'"'"'s responsiveness varies with the magnitude of the current provided to an identified node, and a current source capable of providing nominal and boosted currents is connected to the node. A threshold detector detects the occurrence of an input signal transition prior to its detection by the responsive circuit, and triggers the current source to provide the boosted current; this improves the responsive circuit'"'"'s speed by charging or discharging identified node capacitances which hinder its operation. The identified node can be an input node, an output node, or an internal node. The current source provides the boosted current for a predetermined time interval, or until the input signal crosses a second threshold, enabling response speed to be increased without a significant increase in supply current.
51 Citations
44 Claims
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1. A dynamically boosted current source circuit, comprising:
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an input node, a threshold detector arranged to detect when an input signal connected to said input node crosses a first predetermined threshold, a capacitive node connected such that the speed with which said capacitive node changes state affects the response speed of an associated circuit that is responsive to a transition of said input signal, a boosted node connected such that the current received at said boosted node affects the speed with which said capacitive node changes state, and a current source arranged to provide a first current to said boosted node when said input signal is idle and a boosted current greater than said first current to said boosted node when said threshold detector detects that said input signal has crossed said first predetermined threshold, said current source arranged such that the rate at which its output current is slewed from said first current to said boosted current and the amplitude of said boosted current are independent of the slew rate and amplitude of said input signal, said boosted current increasing the speed with which said capacitive node changes state and there by the speed with which said associated circuit responds to a transition of said input signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A dynamically boosted current source circuit for increasing the speed with which a signal from an open drain or open collector transmitting device is pulled down to a known voltage, comprising:
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an input node having an associated capacitance and connected to receive an input signal from an open drain or open collector transmitting device, a threshold detector arranged to detect when said input signal has crossed a first predetermined threshold voltage, and a current source arranged to provide a first current to said input node when said input signal is above said first predetermined threshold voltage and to provide a boosted current greater than said first current to said input node to pull said input signal down to a known voltage when said input signal falls below said first predetermined threshold voltage, said current source arranged such that the rate at which its output current is slewed from said first current to said boosted current and the amplitude of said boosted current are independent of the slew rate and amplitude of said input signal prior to said current boost, said boosted current increasing the speed with which said associated capacitance is discharged and thereby increasing the speed with which said input node is pulled down to said known voltage.
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16. A dynamically boosted current source circuit for increasing the speed with which a signal from an open drain or open collector transmitting device is pulled up to a known voltage, comprising:
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an input node having an associated capacitance and connected to receive an input signal from an open drain or open collector transmitting device, a threshold detector arranged to detect when said input signal has crossed a first predetermined threshold voltage, and a current source arranged to provide a first current to said input node when said input signal is below said first predetermined threshold voltage and to provide a boosted current greater than said first current to said input node to pull said input signal up to a known voltage when said input signal exceeds said first predetermined threshold voltage, said current source arranged such that the rate at which its output current is slewed from said first current to said boosted current and the amplitude of said boosted current are independent of the slew rate and amplitude of said input signal prior to said current boost, said boosted current increasing the speed with which said associated capacitance is charged and thereby increasing the speed with which said input node is pulled up to said known voltage. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. A dynamically boosted current source circuit for increasing the response speed of a circuit responsive to a transitioning input signal, comprising:
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an input node which receives an input signal, an external circuit which is responsive to a transition of said input signal and which includes at least one capacitive node distinct from said input node, the speed with which said capacitive node changes state affecting the speed with which said external circuit responds to a transition of said input signal, a transition detector arranged to detect a transition of said input signal connected to said input node, and a current source arranged to provide at least one boost current when a transition of said input signal is detected, said boost current connected to boost the current provided to said at least one capacitive node to increase the speed with which said at least one capacitive node changes state and thereby the speed with which said external circuit responds to said input signal transition, said current source arranged such that said at least one boost current'"'"'s slew rate and amplitude are independent of the slew rate and amplitude of said input signal. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36, 37, 38)
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39. A method of improving the response speed of a circuit which has at least one capacitive node and is responsive to a transitioning input signal, comprising the steps of:
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providing a first current to at least one capacitive node in a circuit responsive to a transitioning input signal, the speed with which said capacitive node changes state affecting the speed with which said circuit responds to an input signal transition, detecting when said input signal is transitioning, boosting the current to said at least one capacitive node when an input signal transition is detected to increase the speed with which said capacitive node changes state, said current to said at least one capacitive node boosted at a predetermined rate and to a predetermined amplitude, said predetermined rate and predetermined amplitude independent of the slew rate and amplitude of said input signal. - View Dependent Claims (40, 41, 42, 43, 44)
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Specification