Charge pump phase locked loop with low controlled oscillator gain
Abstract:
A PLL includes a phase-frequency-detector-and-charge-pump-circuit (PFDCPC) receiving a reference signal and divided signal, and generating a charge-pump current. A loop-filter is between output of the PFDCPC and a reference-voltage. A first voltage-to-current converter (V2I1) has low gain, and a second voltage-to-current converter (V2I2) has high gain. A low-gain-path is between outputs of the PFDCPC and V2I1, and a high-gain-path is between the outputs of the PFDCPC and V2I2. A current-controlled-oscillator receives an input signal, and generates an output signal. A loop divider divides the output signal by a divider-value, producing the divided signal. The low-gain-path runs directly from the PFDCPC, through the V2I1, to the input of the current-controlled-oscillator. The high-gain-path runs from the PFDCPC to the loop-filter, from a tap of the loop-filter to a low-pass filter through a current mirror, from a tap of the low-pass filter through the V2I2, to the input of the current-controlled-oscillator.
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