Electric charge pump with wide output voltage area and its servo locking ring

Abstract

The invention concerns a load pump device able to provide a constant current, respectively positive or negative, over an extremely wide output voltage range. A symmetrical switching system activates a first operational amplifier (AOP1) associated with the positive current source or a second amplifier (AOP2) associated with the negative current source according to predetermined threshold values (Vref), the first amplifier being provided so as to restore the behavior of the current mirror (M2, M1) generating a positive current when the output voltage of the device approaches the feed voltage (VDD) and the second amplifier being provided so as to restore the behavior of the current mirror (M4, M3) generating a negative current when the output voltage of the device approaches the earth (GND), thus allowing the output current of the device to be always constant and equal to a reference value (Iref).

Description

technical field [0001] This invention relates to charge pumps capable of providing a wide output voltage range between ground and supply voltage. Background technique [0002] Such a charge pump according to the invention, in particular, enables a maximum adjustment range for a servo phase-locked loop voltage-controlled oscillator and is therefore particularly advantageous for use in radio transmission systems. [0003] A charge pump is a device commonly used in servo phase-locked loops, especially between the phase comparator and the loop filter. A servo phase locked loop or PLL ("phase locked loop") is actually a device consisting of a servo phase oscillator with a phase comparator and corresponding filter. [0004] The servo phase oscillator is used to provide a signal whose phase is servoed to the phase of the reference signal. This involves a voltage-controlled oscillator whose output signal is fed to a phase comparator. The error voltage that may occur in the oscill...

AI Technical Summary

Problems solved by technology

However, under some special operating conditions, there will be a problem: when the output voltage of the charge pump is close to the supply voltage (or ground) of the charge pump, the transistors that form the current sources that generate positive current (or negative current) Entering the linear region, which causes errors in the reproduction of the current, and the output current is no longer maintained at the reference value

[0010] There are some other known different cascode current source schemes, however, in these schemes, the current adaptability between the positive current source and the negative current source is not considered, the difference between the positive current source and the negative current source The inadaptation produces strong spurious oscillations in the output frequency of the oscillator in servo operation

Images