Charge pump circuit reducing noise and charge error and PLL circuit using the same
Operation noise and charge error of a charge pump circuit are reduced, thereby the jitter characteristics and the spectrum characteristics of a PLL circuit are improved, and further a time period elapsed until the PLL circuit is locked is shortened. The charge pump circuit 36 receives a control signal depending on an output of a phase comparison circuit 34 from a control circuit 35 , and comprises a first P-channel MOS transistor P 1 , a second P-channel MOS transistor P 2 and a third P-channel MOS transistor P 3 , and a first N-channel MOS transistor N 1 , a second N-channel MOS transistor N 2 and a third N-channel MOS transistor N 3 , and a first current source 61 , a second current source 62 , a third current source 63 and a fourth current source 64 . The transistor P 1 is turned on and off by an up-signal of the phase comparison circuit 34 , and the transistor N 1 is turned on and off by a down-signal of it, and each of the transistor P 2 , the transistor P 3 , the transistor N 2 and the transistor N 3 is turned on and off on the basis of the control signal of the control circuit 35 , an output signal from a VCO control terminal 65 is input to a VCO 8 through a low pass filter 37 while causing current to flow through the charge pump circuit 36.
1. A charge pump circuit for providing a VCO control output, the charge pump circuit comprising:
a low pass filter having a resistor and a first capacitance that are connected in series between a first output terminal and a ground terminal, and a second capacitance connected in parallel to the first capacitance between the first output terminal and the ground terminal the VCO control output being output from the first output terminal;
a first P-channel MOS transistor having a source, a drain connected to the first output terminal and a gate receiving a first signal;
a first N-channel MOS transistor having a source, a drain connected to the first output terminal and a gate receiving a second signal;
another P-channel MOS transistor having a source, a drain connected to a second output terminal which is connected between the resistor and the first capacitance, and a gate receiving the first signal;
another N-channel MOS transistor having a source, a drain connected to the second output terminal and a gate receiving the second signal;
a first current source for providing a current of first level to the source of the first P-channel MOS transistor;
a second current source for providing a current of second level to the source of the first N-channel MOS transistor;
a third current source for providing a current of third level to the source of the another P-channel MOS transistor; and
a fourth current source for providing a current of fourth level to the source of the another N-channel MOS transistor.
2. A charge pump circuit for receiving control signals from a control circuit that receives a first signal, a second signal and a lock detected signal of a phase comparison circuit output while a phase-locked loop circuit is in the lock state, comprising:
a first P-channel MOS transistor having a source, a drain connected to a first output terminal and a gate receiving the first signal;
a first N-channel MOS transistor having a source, a drain connected to the first output terminal and a gate receiving the second signal;
a second P-channel MOS transistor having a source connected to the source of the first P-channel MOS transistor, a drain and a gate receiving an inverted signal of the first signal while the lock detected signal indicates locking;
a second N-channel MOS transistor having a source connected to the source of the first N-channel MOS transistor, a drain and a gate receiving an inverted signal of the second signal while the lock detected signal indicates locking;
a third P-channel MOS transistor having a source connected to the drain of the second N-channel MOS transistor, a drain connected to a second output terminal and a gate receiving the first signal while the lock detected signal indicates no locking;
a third N-channel MOS transistor having a source connected to the drain of the second P-channel MOS transistor, a drain connected to the second output terminal and a gate receiving the second signal while the lock detected signal indicates no locking;
a first current source for providing a current of first level to the source of the first P-channel MOS transistor;
a second current source for providing a current of second level to the source of the first N-channel MOS transistor;
a third current source for providing a current of third level to the drain of the second N-channel MOS transistor; and
a fourth current source for providing a current of fourth level to the drain of the second P-channel MOS transistor.
3. A phase-locked loop circuit comprising:
a charge pump circuit including:
a first P-channel MOS transistor having a source, a drain connected to an output terminal and a gate receiving a first signal;
a first, N-channel MOS transistor having a source, a drain connected to the output terminal and a gate receiving a second signal;
a second P-channel MOS transistor having a source connected to the source of the first P-channel MOS transistor, a drain and a gate receiving an inverted signal of the first signal;
a second N-channel MOS transistor having a source connected to the source of the first N-channel MOS transistor, a drain and a gate receiving an inverted signal of the second signal;
a first current source for providing a current of first level to the source of the first P-channel MOS transistor;
a second current source for providing a current of second level to the source of the first N-channel MOS transistor;
a third current source for providing a current of third level to the drain of the second N-channel MOS transistor; and
a fourth current source for providing a current of fourth level to the drain of the second P-channel MOS transistor;
a voltage controlled oscillator circuit for outputting a signal having a frequency depending on a voltage level of an input signal from the output terminal;
a reference signal source for generating a reference signal;
a first frequency division circuit for dividing a frequency of the reference signal;
a second frequency division circuit for dividing a frequency of the signal of the voltage controlled oscillator circuit;
a phase comparison circuit for comparing phases of the output signals of both the frequency division circuits to output an up-signal and a down-signal as said first and second signals, and for detecting a lock state to output the lock detected signal;
a control circuit for outputting control signals depending on the up-signal, the down-signal, and the lock detected signal of the phase comparison circuit, said control signals including the inverted first and second signals; and
a low pass filter for attenuating a high frequency component of an output signal at the output terminal of the charge pump circuit to pass only a low frequency component of the output signal to the voltage controlled oscillator circuit.
4. The phase lock loop circuit including the charge pump of claim 1 , and further comprising:
a voltage controlled oscillator circuit for outputting a signal having a frequency depending on a voltage level of an input signal from the VCO control output;
a reference signal source for generating a reference signal;
a first frequency division circuit for dividing a frequency of the reference signal;
a second frequency division circuit for dividing a frequency of the signal of the voltage controlled oscillator circuit;
a phase comparison circuit for comparing phases of the output signals of the first and second frequency division circuits to output an up-signal and a down-signal as said first and second signals, and for detecting a lock state to output a lock detected signal;
a control circuit for outputting control signals based on the up-signal, the down-signal, and the lock detected signal of the phase comparison circuit; and
the low pass filter attentuate a high frequency component of an output signal at the first output terminal of the charge pump circuit 10 pass only a low frequency component to the voltage controlled oscillator circuit.
5. The phase lock loop circuit according to claim 4 , wherein said control circuit is configured to effect the following:
apply said first signal to said another P-channel MOS transistor during an un-locked state indicated by said lock detected signal to turn on said another P-channel MOS transistor to effect charging of said first capacitance using current of said third current source, while simultaneously said first P-channel MOS transistor is turned on by said up-signal to effect charging of said first and second capacitances using said first current source; and
apply said second signal to said another N-channel MOS transistor during the un-locked state indicated by said lock detected signal to turn on said another N-channel MOS transistor to effect discharging of said first capacitance using current of said fourth current source, while simultaneously said first N-channel MOS transistor is turned on by said down-signal to effect discharging charging of said first and second capacitances using said second current source.
6. The phase lock loop circuit including the charge pump of claim 2 , and further comprising:
a voltage controlled oscillator circuit for outputting a signal having a frequency depending on a voltage level of an input signal from the first output terminal;
a reference signal source for generating a reference signal;
a first frequency division circuit for dividing a frequency of the reference signal;
a second frequency division circuit for dividing a frequency of the signal of the voltage controlled oscillator circuit;
the phase comparison circuit for comparing phases of the output signals of the first and second frequency division circuits to output an up-signal and a down-signal as said first and second signals, and for detecting a lock state to output the lock detected signal;
the control circuit for outputting the control signals depending on the up-signal, the down-signal, and the lock detected signal of the phase comparison circuit; and
a low pass filter receiving output from the first and the second output terminals of the charge pump and attenuating a high frequency component of an output signal at the first output terminal of the charge pump circuit to pass only a low frequency component to the voltage controlled oscillator circuit.
7. The phase lock circuit according to claim 6 , wherein:
the low pass filter comprises a resistor and a first capacitance that are connected in series between the first output terminal and a ground terminal, and a second capacitance connected in parallel to the first capacitance between the first output terminal and the ground terminal; and
the second output terminal is connected to a junction between the first capacitance and resistor.