Apparatus and method for controlling charge pump
An apparatus for controlling a charge pump includes a current sensor arranged to output a current sense signal that is linearly proportional to an output current of the charge pump, and an oscillator that provides a clock signal for the charge pump. The oscillator receives the current sense signal and uses it to vary an oscillation frequency of the clock signal. An amplitude of the clock signal also may be varied in response to the current sense signal.
1. An apparatus for controlling a charge pump, comprising:
a current sensing unit arranged to output a current sense signal that is linearly proportional to an output current of a charge pump;
an oscillator unit connected to the current sensing unit and arranged to provide a clock signal for the charge pump, wherein the oscillator unit receives the current sense signal and varies an oscillation frequency of the clock signal in response thereto; and
an oscillation level control unit that receives the current sense signal and varies an amplitude of the clock signal in response thereto,
wherein the oscillation level control unit applies to a resistive load a current responsive to the current sense signal and a predetermined bias current, and generates a voltage responsive thereto.
2. The apparatus of claim 1 , wherein the current sensing unit comprises a current mirror arranged to generate the current sense signal as a predetermined ratio mirror of the output current of the charge pump.
3. The apparatus of claim 1 , wherein the oscillation frequency of the oscillator unit is arranged to increase from a predetermined oscillation frequency in response to the current sense signal.
4. An apparatus for controlling a charge pump, comprising:
a current sensing unit arranged to output a current sense signal that is linearly proportional to an output current of a charge pump; and
an oscillator unit connected to the current sensing unit and arranged to provide a clock signal for the charge pump,
wherein the oscillator unit receives the current sense signal and varies an oscillation frequency of the clock signal in response thereto, wherein the oscillator unit comprises first and second capacitors arranged to each be charged by a current based upon the current sense signal, and
wherein the oscillator unit comprises first and second comparators arranged to receive at respective first inputs a voltage across the first and second capacitors and, at a second input, a reference voltage.
5. The apparatus of claim 4 , wherein the outputs of the first and second comparators are provided to respective inputs of a latch and an output of the latch is arranged to provide a first and second disable signals to disable charging of the first and second capacitors, respectively.
6. The apparatus of claim 1 , wherein the oscillation unit comprises a level shift unit arranged to output a clock signal to the charge pump having an amplitude responsive to the current sense signal.
7. A charge pump comprising the apparatus as claimed in claim 1 .