Optical sensor arrangement and method for light sensing

Patent metadata

Field	Value
Publication number	US-10072976-B2
Application number	US-201414493219-A
Country	US
Kind code	B2
Filing date	Sep 22, 2014
Priority date	Sep 24, 2013
Publication date	Sep 11, 2018
Grant date	Sep 11, 2018

Abstract

An optical sensor arrangement ( 10 ) comprises a light sensor ( 11 ), a current source ( 41 ), an analog-to-digital converter ( 12 ) and a switch ( 44 ) which selectively couples the light sensor ( 11 ) or the current source ( 41 ) to an input ( 14 ) of the analog-to-digital converter ( 12 ).

First claim

I claim:

1. An optical sensor arrangement, comprising:
a light sensor;
a current source;
an analog-to-digital converter; and
a switch which selectively couples the light sensor or the current source to an input of the analog-to-digital converter,
wherein the analog-to-digital converter comprises an amplifier, an integrating capacitor and a reference capacitor,
wherein a first input of the switch is connected to the current source, a second input of the switch is connected to the light sensor and an output of the switch is coupled to an input of the amplifier via the input of the analog-to-digital converter,
wherein the integrating capacitor couples an output of the amplifier to the input of the amplifier,
wherein the reference capacitor is configured for providing a charge package to the input of the amplifier,
wherein the analog-to-digital converter comprises a first, second, third and fourth reference switch,
wherein the first reference switch couples a supply voltage terminal to a first electrode of the reference capacitor,
wherein the first electrode of the reference capacitor is coupled to the input of the amplifier via the fourth reference switch,
wherein the second reference switch couples a reference potential terminal to a second electrode of the reference capacitor, and
wherein the third reference switch couples a first bias source to the second electrode of the reference capacitor.

2. The optical sensor arrangement according to claim 1 , wherein the analog-to-digital converter is configured to generate a first digital output signal representing a value of a calibration current of the current source in a calibration phase and to generate a second digital output signal representing a value of a sensor current of the light sensor in a measurement phase.

3. The optical sensor arrangement according to claim 1 , wherein a value of a calibration current of the current source is set by a trimming signal that is a digital signal.

4. The optical sensor arrangement according to claim 3 , wherein the optical sensor arrangement comprises a memory and the trimming signal is determined by a value stored in the memory.

5. The optical sensor arrangement according to claim 1 , wherein the analog-to-digital converter is realized as a charge balancing analog-to-digital converter.

6. The optical sensor arrangement according to claim 1 , wherein the charge package depends on a capacitance value of the reference capacitor and a voltage value of a supply voltage.

7. The optical sensor arrangement according to claim 1 , wherein the reference capacitor is configured such that a capacitance value of the reference capacitor is set by a trim control signal that is a digital signal.

8. The optical sensor arrangement according to claim 7 , wherein the optical sensor arrangement comprises a control memory and the trim control signal is determined by a value stored in the control memory.

9. A method for light sensing, comprising:
selectively providing a calibration current of a current source or a sensor current of a light sensor to an input of an analog-to-digital converter,
wherein the analog-to-digital converter comprises an amplifier, an integrating capacitor, a reference capacitor, and a first, second, third and fourth reference switch,
wherein a first input of a switch is connected to the current source, a second input of the switch is connected to the light sensor and an output of the switch is coupled to an input of the amplifier via the input of the analog-to-digital converter,
wherein the integrating capacitor couples an output of the amplifier to the input of the amplifier,
wherein the reference capacitor is configured for providing a charge package to the input of the amplifier,
wherein the first reference switch couples a supply voltage terminal to a first electrode of the reference capacitor,
wherein the first electrode of the reference capacitor is coupled to the input of the amplifier via the fourth reference switch,
wherein the second reference switch couples a reference potential terminal to a second electrode of the reference capacitor,
wherein the third reference switch couples a first bias source to the second electrode of the reference capacitor,
wherein the current source is realized as a current mirror and comprises a first and a second current source transistor, and
wherein the first current source transistor couples the switch to the reference potential terminal.

10. The method according to claim 9 , wherein the analog-to-digital converter generates a first digital output signal representing a value of the calibration current in a calibration phase and to generate a second digital output signal representing a value of the sensor current in a measurement phase.

11. The method according to claim 9 , wherein a value of a calibration current is set by a trimming signal that is a digital signal.

12. The method according to claim 9 , wherein the analog-to-digital converter is realized as a charge balancing analog-to-digital converter that comprises the reference capacitor having a capacitance value set by a trim control signal that is a digital signal.

13. An optical sensor arrangement, comprising:
a light sensor;
a current source;
an analog-to-digital converter; and
a switch which selectively couples the light sensor or the current source to an input of the analog-to-digital converter,
wherein the analog-to-digital converter comprises an amplifier and the switch is coupled to an input of the amplifier via the input of the analog-to-digital converter,
wherein the analog-to-digital converter comprises a reference capacitor which is configured for providing a charge package to the input of the amplifier,
wherein the reference capacitor is configured such that a capacitance value of the reference capacitor is set by a trim control signal that is a digital signal,
wherein the analog-to-digital converter comprises a first, second, third and fourth reference switch,
wherein the first reference switch couples a supply voltage terminal to a first electrode of the reference capacitor,
wherein the first electrode of the reference capacitor is coupled to the input of the amplifier via the fourth reference switch,
wherein the second reference switch couples a reference potential terminal to a second electrode of the reference capacitor, and
wherein the third reference switch couples a first bias source to the second electrode of the reference capacitor.

14. An optical sensor arrangement, comprising:
a light sensor;
a current source;
an analog-to-digital converter; and
a switch which selectively couples the light sensor or the current source to an input of the analog-to-digital converter,
wherein the current source is realized as a current mirror and comprises a first and a second current source transistor,
wherein the first current source transistor couples the switch to a reference potential terminal,
wherein the analog-to-digital converter comprises an amplifier, a reference capacitor and a first, second, third and fourth reference switch,
wherein the amplifier comprises an input connected to the input of the analog-to-digital converter,
wherein the first reference switch couples a supply voltage terminal to a first electrode of the reference capacitor,
wherein the first electrode of the reference capacitor is coupled to the input of the amplifier via the fourth reference switch,
wherein the second reference switch couples the reference potential terminal to a second electrode of the reference capacitor, and
wherein the third reference switch couples a first bias source to the second e

Assignees

• Ams Ag

Inventors

• Xu Gonggui

Classifications

• H03M1/10

  Calibration or testing · CPC title

• G01J1/46 Primary

  using a capacitor · CPC title

• G01J1/18

  using comparison with a reference electric value · CPC title

• H03M1/12

  Analogue/digital converters ({H03M1/001 – } H03M1/10 take precedence) · CPC title

• G01J2001/444

  Compensating; Calibrating, e.g. dark current, temperature drift, noise reduction or baseline correction; Adjusting · CPC title