On-chip power supply interface with load-independent current demand
First Claim
1. An interface circuit for use between a power supply pin and internal circuitry with a variable load, the interface circuit providing a substantially load-independent current demand at the power supply pin, the interface circuit comprising:
- sensing means, coupled between the power supply pin at an interface input and the internal circuitry at an interface output, for sensing a current load of the internal circuitry and producing a control voltage corresponding to said current load; and
current sinking means, responsive to said control voltage, for sinking extra current in inverse relation to said current load of the internal circuitry, such that total current demand by both the internal circuitry and the extra current sinking means is at least substantially constant up to saturation of said current sinking means.
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Accused Products
Abstract
An on-chip interface circuit located between the chip'"'"'s power supply pin and its internal circuitry senses the current load of the internal circuitry and provides a supplemental current sink so that total current demand seen at the power supply pin is substantially constant despite the internal circuitry'"'"'s variable load. Sensing of the internal load is done by a sensor stage with two parallel branches, each branch having a resistor, a sense transistor, and a current mirror device, which together produce a voltage drop as a control voltage output which relates the internal load to a constant reference current. The supplemental current sink is in the form of a transistor operating below saturation in its linear region and whose gate is coupled to receive the control voltage output of the sensor stage.
20 Citations
12 Claims
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1. An interface circuit for use between a power supply pin and internal circuitry with a variable load, the interface circuit providing a substantially load-independent current demand at the power supply pin, the interface circuit comprising:
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sensing means, coupled between the power supply pin at an interface input and the internal circuitry at an interface output, for sensing a current load of the internal circuitry and producing a control voltage corresponding to said current load; and current sinking means, responsive to said control voltage, for sinking extra current in inverse relation to said current load of the internal circuitry, such that total current demand by both the internal circuitry and the extra current sinking means is at least substantially constant up to saturation of said current sinking means. - View Dependent Claims (2, 3, 4, 5)
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6. An interface circuit for use between a power supply pin and internal circuitry with a variable load, the interface circuit providing a substantially load-independent current demand at the power supply pin, the interface circuit comprising:
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a reference current stage having a constant current source and a current mirror device in series establishing a constant reference current therethrough; a load sensing stage coupled between the power supply pin at an interface input and the internal circuitry at an interface output, the load sensing stage including first and second branches connected in parallel between the interface input and ground, each branch having a resistor, a sense transistor and a current mirror device, the current mirror devices in the two branches and the current mirror device in the reference current stage having the gates of the current mirror devices coupled together to establish current flow through the mirror devices of the two branches which correspond to the constant reference current, the sense transistors of the two branches having a common gate connection between the sense transistor and current mirror device of the first branch, said resistor of the first branch providing substantially larger resistance than said resistor in the second branch, the interface output being coupled between the resistor and sense transistor of the second branch such that current flow through the resistor in the second branch provides a measure of the current load of the internal circuitry in the form of a voltage drop, the voltage drop being provided as a control voltage that is output from the load sensing stage between the sense transistor and current mirror device of the second branch; and a supplemental load stage including a transistor connected between the interface output and ground, the transistor having a gate coupled to receive the control voltage output from the load sensing stage, the transistor operating below saturation in a substantially linear region of an operating characteristic of the transistor such that the transistor sinks extra current in inverse relation to the current load of the internal circuitry.
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7. A method of providing a substantially load-independent current demand at a power supply pin of an integrated circuit notwithstanding a variable load by internal circuitry of the integrated circuit, the method comprising:
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sensing, by an interface circuit provided between the power supply pin and the internal circuitry, a current load of the internal circuitry and producing a control voltage corresponding to the sensed current load; and sinking, by a supplemental load device of the interface circuit responsive to the control voltage, extra current in inverse relation to the current load of the internal circuitry, such that total current demand by both the internal circuitry and the supplemental load device is substantially constant up to a saturation level of the supplemental load device. - View Dependent Claims (8, 9, 10)
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11. An integrated circuit comprising:
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at least one power supply pin; internal circuitry drawing current through the power supply pin; and an interface circuit electrically coupled between the power supply pin and the internal circuitry and providing a supplemental current load such that total current demand by both the internal circuitry and interface circuit is substantially constant at the power supply pin notwithstanding any current load variation by the internal circuitry. - View Dependent Claims (12)
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Specification