Charge pump for PLL/DLL
First Claim
Patent Images
1. A locked loop comprising:
- a phase detector for providing an up output signal and a down output signal;
a charge pump comprising;
pull-up circuitry that comprises a current source and a controlled transistor having a gate adapted for connection to the up output signal for being controlled thereby, the pull-up circuitry connected between a positive voltage supply and an output node of the charge pump;
pull-down circuitry that comprises a current source and a controlled transistor having a gate adapted for connection to the down output signal for being controlled thereby, the pull-down circuitry connected between a ground voltage supply and the charge pump output node;
a reference current source for controlling the current in the current sources of the pull-up and pull-down circuitries;
an operational amplifier having two inputs and an output, and the operational amplifier configured to reduce phase error, one of the inputs of the operational amplifier connected to the charge pump output node; and
a startup circuit to establish a predetermined voltage level at the charge pump output node during startup; and
a capacitor connected to the charge pump output node.
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Abstract
A charge pump for use in a locked loop minimizes static phase error through the use of an operational amplifier. The operational amplifier also mitigates the effects of low power supply voltage. The charge pump further includes a startup circuit to establish a predetermined voltage level at the charge pump output node during startup.
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Citations
24 Claims
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1. A locked loop comprising:
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a phase detector for providing an up output signal and a down output signal; a charge pump comprising; pull-up circuitry that comprises a current source and a controlled transistor having a gate adapted for connection to the up output signal for being controlled thereby, the pull-up circuitry connected between a positive voltage supply and an output node of the charge pump; pull-down circuitry that comprises a current source and a controlled transistor having a gate adapted for connection to the down output signal for being controlled thereby, the pull-down circuitry connected between a ground voltage supply and the charge pump output node; a reference current source for controlling the current in the current sources of the pull-up and pull-down circuitries; an operational amplifier having two inputs and an output, and the operational amplifier configured to reduce phase error, one of the inputs of the operational amplifier connected to the charge pump output node; and a startup circuit to establish a predetermined voltage level at the charge pump output node during startup; and a capacitor connected to the charge pump output node. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A locked loop comprising:
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a phase detector for providing an up output signal and a down output signal; a charge pump comprising; pull-up circuitry that comprises a current source and a controlled transistor having a gate adapted for connection to the up output signal for being controlled thereby, the pull-up circuitry connected between a positive voltage supply and an output node of the charge pump; pull-down circuitry that comprises a current source and a controlled transistor having a gate adapted for connection to the down output signal for being controlled thereby, the pull-down circuitry connected between a ground voltage supply and the charge pump output node; a reference current source; and a plurality of programmable transistors, both the reference current source and the plurality of programmable transistors each configured to control the current in at least one of the current sources of the pull-up and pull-down circuitries; a capacitor connected to the charge pump output node; and a startup circuit connected to the charge pump output node, and the startup circuit comprising a MOS device having a source connected to a voltage supply and a gate connected to a startup control signal. - View Dependent Claims (22, 23, 24)
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Specification