Fast power-on bias circuit
AssigneeRambus Inc.
InventorsWayne Dettloff, John Wilson, Lei Luo, Brian Leibowitz, Jared Zerbe, Pravin Kumar Venkatesan
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Abstract
Conventional bias circuits exhibit a number of limitations, including the time required to power-up a bias circuit following a low-power state. Large current surges in the supply network induce ringing, further complicating a power-up process. Example embodiments reduce power-up time and minimize current surges in the supply by selectively charging and discharging capacitance to the circuit during power-up and power-down of the bias circuit.
Claims29
A method of operating a bias circuit providing a bias voltage at a bias node, comprising:
- connecting a bias node to a first voltage;
- charging a capacitor that is disconnected from the bias node to a second voltage different from the first voltage during a power-down mode of a bias circuit;
- and
- coupling the capacitor to the bias node, the capacitor charging the bias node toward a bias voltage as the bias circuit transitions from the power-down mode to a power-up mode;
- comparing a parameter of the bias circuit against a reference value;
- and
- adjusting capacitance of the capacitor based on the comparison.
A bias circuit to provide a bias voltage, comprising:
- a bias node;
- a first switch configured to connect the bias node to a first voltage during a power-down mode;
- a capacitor;
- a second switch configured to connect the capacitor to a second voltage during the power-down mode;
- a third switch configured to couple the capacitor to the bias node during power-up of the bias circuit, the capacitor drawing the voltage of the bias node toward a bias voltage;
- and
- a comparator configured to compare a parameter of the bias circuit against a reference value, the capacitor having a capacitance based on the comparison.
A method of operating a bias circuit providing a bias voltage at a bias node, comprising:
- connecting a bias node to a first voltage;
- charging a capacitor that is disconnected from the bias node to a second voltage different from the first voltage during a power-down mode of a bias circuit;
- and
- coupling the capacitor to the bias node, the capacitor charging the bias node toward a bias voltage as the bias circuit transitions from the power-down mode to a power-up mode;
- wherein the bias circuit is a first bias circuit, and further comprising:
- powering-up a second bias circuit at a time T following power-up of the first bias circuit, the time T selected to minimize ringing at a power supply common to the first and second bias circuits.
A method of operating a bias circuit providing a bias voltage at a bias node, comprising:
- connecting a bias node to a first voltage;
- comparing a detected voltage against a reference voltage, the detected voltage being relative to a voltage of the bias node;
- selecting a capacitance value of a capacitor based on the comparison, the capacitor being disconnected from the bias node;
- charging the capacitor to a second voltage different from the first voltage during a power-down mode of a bias circuit;
- and
- coupling the capacitor to the bias node, the capacitor charging the bias node toward a bias voltage as the bias circuit transitions from the power-down mode to a power-up mode.
Dependencies are inferred from the claim text.