A current-adjustable charge pump circuit

Abstract

The present invention relates to a current-adjustable charge pump circuit comprises a charge pump current regulating circuit which is connected to the external current source and a charge pump switching circuit connected with the charge pump current regulating circuit. The invention is characterized in that the charge pump current regulating circuit is composed of a NMOS current mirror circuit and a PMOS current mirror circuit which are connected. The NMOS current mirror circuit and PMOS current mirror circuit are respectively composed of a current mirror source tube branch line and a current mirror image tube branch line which are correspondingly connected with a switching tube. A relatively-fixed proportional dimension is provided between the mirror source tube and the mirror image tube on the corresponding branch line. The number of the mirror source branch line or the mirror image branch line is selected through the controlling of the control signal to the on-off of the control switching tube, thereby the output currents of the NMOS current mirror circuit and PMOS current mirror current are changed. The regulation to the charging current and discharging current of the charge pump is realized through the charge pump switching circuit. The invention not only can conveniently and smartly regulate the current of the charge pump, but also can regulate to obtain a current which has a relationship that the current is a fractional part of the input current source.

Description

technical field [0001] The invention relates to a charge pump circuit, in particular to a charge pump circuit with adjustable current, which is mainly applied to a charge pump integrated module in an integrated phase-locked loop. Background technique [0002] The application of the charge pump phase-locked loop is very extensive. Generally speaking, the charge pump in the phase-locked loop is composed of two current sources with switches, and the output of the pre-stage frequency or phase detector (PFD) determines the switch. The opening and closing of the circuit, so as to decide whether to pump the charge into the loop filter of the subsequent stage or pump the charge out of the loop filter of the subsequent stage, and the resulting control voltage (vctrl) to control the post-stage loop filter stage voltage controlled oscillator (vco). The reason why the current of the charge pump circuit is adjustable is to flexibly adjust the above-mentioned control voltage (vctrl), so ...

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Problems solved by technology

If the current of the charge pump circuit is fixed, the oscillation frequency of the charge pump phase-locked loop can only be adjusted by adjusting the loop filter or the voltage-controlled oscillator, but the transfer function of the entire phase-locked loop will change greatly, which is not conducive to the overall The control and adjustment of the loop is very inconvenient; if the current in the charge pump circuit is changed by changing the width and length of the current mirror tube, it can only be achieved by increasing the number of current mirror tubes connected in parallel on the basis of the original reference current source. Increase the size of the current, but cannot reduce the size of the current, and each modification also needs to involve the modification of the layout, which is also very inconvenient

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