Charge pump circuit and PLL circuit using same
View Patent ↗A charge pump circuit able to enhance the rising and falling characteristics of a current output, drive the current output with a short pulse, reduce leakage current at the OFF time when a current is not output, and realize a reduction of a power consumption and a PLL circuit using same. By outputting a charge current or a discharge current in accordance with an up signal or a down signal and turning on a third transistor (PC, NC) at the OFF time when the current is not output, an inverse bias voltage is supplied between a gate and a source of the second transistor (PA, NA), whereby a reduction of the leakage current can be realized. When the second or third transistor is switched in accordance with the up signal or the down signal, the timing of the control signal is appropriately controlled, simultaneous turning on of the second and third transistors can be avoided, release or injection of charges from and to the output terminal of the charge pump circuit can be prevented, and the stability of an oscillation frequency of a VCO can be improved.
1. A charge pump circuit for outputting a current in an effective period in accordance with an input signal held at a first level in said effective period and held at a second level in a period other than said effective period, comprising:
first and second transistors connected in series between a first power supply terminal and an output terminal of the charge pump circuit;
a third transistor connected between a connection point of said first and second transistors and a second power supply terminal; and
a control signal generation circuit,
wherein said control signal generation circuit:
generates a first control signal for turning said first transistor on in said effective period and for turning off said first transistor other than this in accordance with said input signal and supplying the first control signal to the control terminal of said first transistor,
generates a second control signal for turning said second transistor on before said first transistor is turned on, turning off said second transistor after said first transistor is turned off, holding a level where a desired output current flows when said second transistor is on, and supplying the second control signal to the control terminal of said second transistor, and
generates a third control signal for turning off said third transistor before said second transistor is turned on, turning on said third transistor after said second transistor is turned off, and supplying the third control signal to the control terminal of said third transistor, and
wherein said first, second and third control signals are generated by said control generation circuit in accordance with a preliminary input signal having a phase advanced from said input signal.
2. A charge pump circuit as set forth in claim 1 , wherein
said control signal generation circuit has a buffer for delaying said input signal by exactly a predetermined delay time and a logic gate for performing a logic operation in accordance with said input signal and an output signal of said buffer; and
said first control signal is generated in accordance with the output signal of said buffer and said second control signal is generated in accordance with the output signal of said logic gate.
3. A charge pump circuit as set forth in claim 2 , wherein said control signal generation circuit switches the level of said third control signal in accordance with said preliminary input signal, turns off said third transistor, switches the level of said third control signal in accordance with said second control signal, and turns said third transistor on.
4. A charge pump circuit as set forth in claim 1 , wherein an inverse bias voltage is supplied between a gate and a source of said second transistor.