System and method for a programmable voltage source

Patent metadata

Field	Value
Publication number	US-9281744-B2
Application number	US-201213460025-A
Country	US
Kind code	B2
Filing date	Apr 30, 2012
Priority date	Apr 30, 2012
Publication date	Mar 8, 2016
Grant date	Mar 8, 2016

Abstract

In accordance with an embodiment, a method of operating a charge pump includes providing a first programmable voltage to a plurality of clock generators having outputs coupled to first nodes of corresponding groups of charge pump capacitors, and selecting a second node of one capacitor from one of the corresponding groups of charge pump capacitors. The clock generators produce a plurality of clock signals having amplitudes proportional to the first programmable voltage.

First claim

What is claimed is:

1. A method of operating a charge pump, the method comprising:
providing a first programmable voltage to a plurality of clock generators having outputs coupled to first nodes of corresponding groups of charge pump capacitors, the clock generators producing a plurality of clock signals having amplitudes proportional to the first programmable voltage;
selecting a second node of one capacitor from one of the corresponding groups of charge pump capacitors;
coupling the selected second node to an output of the charge pump; and
adjusting an output impedance of the charge pump, wherein adjusting the output impedance of the charge pump further adjusts an output voltage of the charge pump, and adjusting the output impedance of the charge pump comprises adjusting a current of a current source coupled to the output of the charge pump.

2. The method of claim 1 , wherein providing the first programmable voltage comprises coupling an output of a digital to analog (D/A) converter to the first nodes of the corresponding groups of charge pump capacitors.

3. The method of claim 1 , wherein:
providing the first programmable voltage controls an output voltage of the charge pump according to a first voltage granularity; and
selecting the second node of the one capacitor controls the output voltage of the charge pump according to a second voltage granularity, wherein the second voltage granularity is more coarse than the first voltage granularity.

4. The method of claim 1 , wherein adjusting the current source comprises adjusting the current according to a difference between a voltage proportional to the output voltage of the charge pump and the first programmable voltage.

5. The method of claim 1 , further comprising:
coupling the output of the charge pump to a bias terminal of a capacitive signal source.

6. The method of claim 5 , wherein the capacitive signal source comprises a MEMS microphone.

7. A programmable voltage source comprising:
a programmable voltage generator producing a first voltage at an output node;
a multi-stage charge pump, the multi-stage charge pump comprising:
a first clock generator coupled to the programmable voltage generator, wherein the first clock generator is configured to generate a first clock signal having an amplitude proportional to the first voltage;
a second clock generator coupled to the programmable voltage generator, wherein the second clock generator is configured to generate a second clock signal having an amplitude proportional to the first voltage;
a first group of capacitors having a first node coupled to the first clock signal;
a second group of capacitors having a first node coupled to the second clock signal;
output coupling switches coupled between second nodes of capacitors of the first and second group of capacitors and an output of the programmable voltage source; and
an output switch controller configured to activate one of the output coupling switches.

8. The programmable voltage source of claim 7 , wherein the programmable voltage generator comprises a digital to analog (D/A) converter.

9. The programmable voltage source of claim 7 , wherein stages of the multi-stage charge pump comprises a functional diode coupled between two capacitors.

10. The programmable voltage source of claim 9 , wherein the functional diode is a MOS pass transistor.

11. The programmable voltage source of claim 7 , wherein the multi-stage charge pump comprises a Dickson charge pump.

12. The programmable voltage source of claim 7 , further comprising a decoder coupled to between a coarse digital input and control nodes of the output coupling switches.

13. The programmable voltage source of claim 7 , further comprising:
a controllable current source coupled to the output of the programmable voltage source; and
a current control circuit coupled to a control node of the controllable current source, the current control circuit adjusting the controllable current source based on a voltage at the output of the programmable voltage source and the first voltage.

14. The programmable voltage source of claim 13 , wherein the current control circuit comprises:
a voltage downscaler having an input coupled to the output of the programmable voltage source; and
an error amplifier having a first input coupled to an output of the voltage downscaler, a second input coupled to the first voltage, and an output coupled to the control node of the controllable current source.

15. The programmable voltage source of claim 7 , wherein:
the programmable voltage generator provides fine control of a voltage at the output of the programmable voltage source; and
the output coupling switches provides coarse control of the voltage at the output of the programmable voltage source.

16. A system comprising:
a programmable voltage source comprising
a digital to analog (D/A) converter;
a plurality of clock generators coupled to an output of the D/A converter, the plurality of clock generators configured to produce a clock signal having an amplitude proportional to a first signal at the output of the D/A converter;
a multi-stage charge pump coupled to the plurality of clock generators, the multi-stage charge pump producing an output voltage proportional to the first signal;
a switching network comprising switches, wherein each switch of the switching network comprises a first end coupled to a corresponding capacitor within the multi-stage charge pump, and a second end coupled to an output node of the programmable voltage source;
a switching network controller configured to activate a switch of the switching network;

a controllable current source coupled to the output node of the programmable voltage source; and
a current control circuit coupled to a control node of the controllable current source, the current control circuit adjusting the controllable current source based on a voltage at the output of the programmable voltage source and the first signal.

17. The system of claim 16 , further comprising an up/down counter coupled to an input of the D/A converter.

18. The system of claim 16 , wherein the multi-stage charge pump comprises a Dickson charge pump.

19. The system of claim 16 , wherein the programmable voltage source is disposed on an integrated circuit.

20. The system of claim 16 , further comprising a MEMS microphone coupled to an output of the programmable voltage source.

21. The system of claim 16 , wherein:
the D/A converter comprises an input coupled to a first digital input bus, the first digital input bus providing fine control of a voltage at the output node of the programmable voltage source; and
the switching network comprises an input coupled to a second digital input bus, the second digital input bus providing coarse control of the voltage at the output node of the programmable voltage source.

Assignees

• Kropfitsch Michael
• Infineon Technologies Ag

Inventors

• Kropfitsch Michael

Classifications

• H02M3/073 Primary

  Charge pumps of the Schenkel-type · CPC title

• H03K19/00

  Logic circuits, i.e. having at least two inputs acting on one output (circuits for computer systems using fuzzy logic G06N7/02); Inverting circuits · CPC title

• H03K17/687

  the devices being field-effect transistors · CPC title

• H03K4/00 Primary

  Generating pulses having essentially a finite slope or stepped portions · CPC title

• H04R19/04 Primary

  Microphones (H04R19/01 takes precedence) · CPC title