Oscillator circuit and method for generating an oscillator signal

Patent metadata

Field	Value
Publication number	US-9362922-B2
Application number	US-201314420336-A
Country	US
Kind code	B2
Filing date	Aug 8, 2013
Priority date	Aug 9, 2012
Publication date	Jun 7, 2016
Grant date	Jun 7, 2016

Abstract

The present invention relates to an oscillator circuit, comprising a switched capacitor circuit comprising a parallel circuit with a current input to be supplied with a reference current on one side and being connected to a reference terminal on the other side. The parallel circuit further comprises a first capacitor in a first branch and, in a second branch, a second capacitor connected in-between a first and second switch. A switch control unit comprises a first input coupled to the current input of the parallel circuit and a second input to be supplied with a reference voltage as well as an oscillator output for providing an oscillator signal. The switch control unit is being designed to operate the first and second switch such that, in a charging phase, the first and second capacitor is charged to a respective level depending on the reference voltage and, in a discharging phase, the charge stored on the first capacitor is discharged using the charge stored on the second capacitor.

First claim

The invention claimed is:

1. An Oscillator circuit, comprising:
a switched capacitor circuit comprising a parallel circuit with a current input to be supplied with a reference current on one side and being connected to a reference terminal on the other side, wherein the parallel circuit further comprises a first capacitor in a first branch and, in a second branch, a second capacitor connected in-between a first and second switch, and
a switch control unit comprising a first input coupled to the current input of the parallel circuit and a second input to be supplied with a reference voltage, and further comprising an oscillator output for providing an oscillator signal, wherein the switch control unit is being designed to operate the first and second switch such that, in a charging phase, the first and the second capacitor are charged in parallel with the reference current to a respective level depending on the reference voltage and, in a discharging phase, the charge stored on the first capacitor is discharged using the charge stored on the second capacitor.

2. The oscillator circuit according to claim 1 , further comprising a reference generator to generate the reference current and to generate the reference voltage, wherein
a reference current output is coupled to the current input of the parallel circuit to supply the reference current, and
a reference voltage output is coupled to the second input of the switch control unit.

3. The oscillator circuit according to claim 1 , wherein the reference generator is a temperature compensated reference generator, in particular a bandgap reference generator.

4. The oscillator circuit according to claim 1 , wherein
the reference current output of the reference generator is connected to an input side of a load current generator and
an output side of the load current generator is connected to the current input of the parallel circuit.

5. The oscillator circuit according to claim 4 , wherein the load current generator comprises a trimming input to trim the reference current and provide a trimmed reference current at the current input.

6. The oscillator circuit according to claim 1 , wherein the first and second capacitors have the same capacity.

7. The oscillator circuit according to claim 1 , wherein the switch control unit comprises a comparator comprising the first and second input and comprising an output to provide a control signal.

8. The oscillator circuit according to claim 7 , wherein the first input of the comparator is electrically connected to the current input in both charging and discharging phase.

9. The oscillator circuit according to claim 7 , wherein the switch control unit comprises a flip-flop further comprising
a first flip-flop input is connected to the output of the comparator and
a first flip-flop output is connected to the oscillator output for providing the oscillator signal.

10. The oscillator circuit according to claim 9 , wherein the first flip-flop output
is coupled to the first and second switch and
outputs a logic signal to operate the first and second switch.

11. The oscillator circuit according to claim 1 , comprising a third switch which is grounded and coupled to the second capacitor such that during a reset phase the first and second capacitors are set to a ground potential, and wherein third grounded switch is operated depending on a reset signal.

12. A method for generating an oscillator signal, comprising the steps of:
generating a reference current and a reference voltage,
in a charging phase, charging in parallel with the reference current, a first and second capacitor to a respective level depending on the reference voltage,
in a discharging phase, discharging the charge stored on the first capacitor using the charge stored on the second capacitor, wherein the first capacitor is charged with the reference current during both the charging and discharging phase, and
generating an oscillator signal depending on the charge stored on the first capacitor.

13. The method for generating an oscillator signal according to claim 12 , wherein reference current and a reference voltage are provided in a temperature compensated manner.

14. The method for generating an oscillator signal according to claim 12 , wherein
an oscillation period of the oscillator signal results from succession of a charging phase and discharging phase and
the oscillator signal is generated by at least one cycle of succeeding charging phase and discharging phase.

Assignees

• Ams Ag

Inventors

• Schatzberger Gregor

Classifications

• H03K3/0231

  Astable circuits {(H03K3/0315 takes precedence)} · CPC title

• H03K4/502 Primary

  the capacitor being charged from a constant-current source · CPC title

• H03L1/02 Primary

  against variations of temperature only · CPC title