On-chip regulator with variable load compensation
An integrated circuit includes a voltage regulator to supply a regulated voltage and a data output that couples to an unterminated transmission line. The circuit draws a variable amount of power from the voltage regulator according to the data. The voltage regulator includes a first current generation circuit to provide a data transition-dependent current.
1. An integrated circuit comprising:
a voltage regulator to supply a regulated voltage;
a circuit to process data, the circuit drawing a variable amount of power from the voltage regulator according to the data;
wherein the voltage regulator comprises
a first current source to provide a calibrated current that is dependent on the data, and
a second current source to provide a supplemental current in dependence on a difference between the current required by the circuit and the calibrated, data-dependent current.
2. The integrated circuit according to claim 1 wherein the first current source provides the calibrated, data-dependent current in dependence upon a calibration setting.
3. The integrated circuit according to claim 2 further comprising a register, and wherein the calibration setting is programmed into the register.
4. The integrated circuit according to claim 1 wherein the first current source is an open-loop current source and the second current source is a closed-loop current source.
5. The integrated circuit according to claim 4 wherein the open-loop current source is selectively enabled to provide the calibrated current based on data to be transmitted to another integrated circuit.
6. The integrated circuit according to claim 5 and further including a register, coupled to the open-loop current source to store the calibration setting.
7. The integrated circuit according to claim 4 wherein the closed-loop current source includes a comparator having a reference input, and a regulation voltage input for comparison to the reference input.
8. The integrated circuit according to claim 1 wherein the calibrated, data-dependent current is enabled in response to the transmitted data, the transmitted data represented by at least a predetermined threshold level.
9. The integrated circuit according to claim 1 wherein the calibrated, data-dependent current is enabled in response to the transmitted data, the transmitted data represented by transitions in successive data bits.
10. A transmitter integrated circuit comprising:
a voltage regulator to supply a regulated voltage;
a driver circuit to transmit data at a signal swing corresponding to the regulated voltage and a load current;
wherein the voltage regulator comprises a source to supply a current that is dependent on the data; and to the driver circuit based on at least one calibration setting and wherein the voltage regulator further comprises a source of supplemental current to supply supplemental current to the driver circuit based on the difference between the actual load current and current needed by the driver circuit.
11. The transmitter integrated circuit according to claim 10 wherein the source to supply a data-dependent current comprises an open-loop current source.
12. The transmitter integrated circuit according to claim 10 wherein the source of supplemental current comprises a closed-loop current source circuit.
13. The transmitter integrated circuit according to claim 12 wherein the closed-loop current source circuit comprises:
a comparator having
a reference voltage input,
a second input to receive the regulator voltage, and
a comparator output; and
a second current source to generate the supplemental current, the second current source responsive to comparisons between the reference voltage and the regulator voltage to adjust the supplemental current.
14. The transmitter integrated circuit according to claim 10 wherein the data-dependent current is based on an internal calibration of the load current.
15. The transmitter integrated circuit according to claim 14 wherein the data-dependent current is based on an external impedance having a known value.