Self-adjusting startup control for charge pump current source in phase locked loop
First Claim
1. In an integrated circuit phase-locked loop (PLL) including a divide-by-N counter, a phase comparator, a voltage-controlled oscillator, and a charge pump having a bias current source, a bias control circuit comprising:
- a bias checking circuit for indicating when said bias current source in said charge pump has stabilized; and
a bias activation circuit to control the operation of said bias current source.
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Accused Products
Abstract
A circuit and a method are provided for reducing power consumption in a phase-locked loop (PLL) by controlling how long the bias current for the charge pump is turned on. In such a circuit, a bias check circuit that indicates when the bias current has stabilized, and a self-adjusting control circuit including an internal counter are provided to measure how long the bias current takes to start up when the PLL is locked. Then the self-adjusting control circuit prevents the bias current from turning on until there is just enough time for it to stabilize before a charge pump event. A default control circuit is also provided to turn the bias current on for specified intervals when the PLL is out of lock.
89 Citations
11 Claims
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1. In an integrated circuit phase-locked loop (PLL) including a divide-by-N counter, a phase comparator, a voltage-controlled oscillator, and a charge pump having a bias current source, a bias control circuit comprising:
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a bias checking circuit for indicating when said bias current source in said charge pump has stabilized; and a bias activation circuit to control the operation of said bias current source. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for controlling the activation of a bias current in a PLL having a charge pump and bias circuit in order to reduce power consumption in said PLL comprising the steps of:
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(i) when said PLL is locked; measuring the time required for said bias current to stabilize after being turned on; turning on said bias current just long enough before the operation of said charge pump to allow said bias current to stabilize; (ii) when said PLL is out of lock; turning on said bias current for the minimum time that would be required if the charge pump were operating at maximum frequency.
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Specification