APPARATUS AND METHOD FOR PHASE LOCK LOOP GAIN CONTROL
First Claim
1. A gain compensator circuit that determines a reference pump current for a charge pump in a phase lock loop (PLL), comprising:
- a plurality of unit current sources that are arranged into at least one group, said group responsive to a capacitor control signal and generating a portion of the reference pump current when said group is activated, wherein said capacitor control signal also controls a corresponding fixed capacitor; and
means for scaling said unit current sources responsive to a phase lock loop control signal.
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Accused Products
Abstract
A gain compensator compensates for the gain variation of a varactor-tuned voltage tuned oscillator (VCO) in a phase lock loop (PLL). The VCO includes a parallel LC circuit having multiple fixed capacitors that can be switched-in or switched-out of the LC circuit according to a capacitor control signal to perform band-select tuning of the VCO. The gain compensator compensates for the variable VCO gain by generating a charge pump reference current that is based on the same capacitor control signal that controls the fixed capacitors in the LC circuit. The gain compensator generates the charge pump reference current by replicating a reference scale current using unit current sources. The number of times the reference scale current is replicated is based on the fixed capacitance that is switched-in to the LC circuit and therefore the frequency band of the PLL. The reference scale current is generated based on a PLL, control that specifics certain PLL characteristics such as reference frequency, loop bandwidth, and loop damping. Therefore, the reference pump current can be efficiently optimized for-changing PLL operating conditions, in addition to compensating for variable VCO gain.
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Citations
2 Claims
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1. A gain compensator circuit that determines a reference pump current for a charge pump in a phase lock loop (PLL), comprising:
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a plurality of unit current sources that are arranged into at least one group, said group responsive to a capacitor control signal and generating a portion of the reference pump current when said group is activated, wherein said capacitor control signal also controls a corresponding fixed capacitor; and
means for scaling said unit current sources responsive to a phase lock loop control signal.
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2-35. -35. (canceled)
Specification