Circuit architecture for mode switch

Patent metadata

Field	Value
Publication number	US-9733275-B2
Application number	US-201514808148-A
Country	US
Kind code	B2
Filing date	Jul 24, 2015
Priority date	Jul 25, 2014
Publication date	Aug 15, 2017
Grant date	Aug 15, 2017

Abstract

A current detection module capable of differentiating and quantifying contribution to a current signal generated by a sensor in response to stimulation by a certain target source from contributions from sources other than the target source (ambient sources) is disclosed. As long as the contribution from the target source comprises a pulsed signal, the module may synchronize itself to the pulse(s) so that there is a predetermined phase relationship between the pulse(s) and functions carried out by various stages of the module. The module may be re-used to also detect and quantify contributions from ambient sources by presenting these contributions to the module as pulses that trigger synchronization of the module. To that end, a detection system disclosed herein is based on the use of such current detection module and allows mode switching where, depending on the selected mode of operation, the module is configured to perform different measurements.

First claim

What is claimed is:

1. A detection system comprising:
a sensor configured to generate a current signal, the current signal comprising at least a first portion comprising a contribution from a target source and/or a second portion comprising a contribution from one or more sources other than the target source;
a current detection module configured to receive the current signal generated by the sensor and generate a digital value indicative of the first portion of the current signal and/or a digital value indicative of the second portion of the current signal; and
a mode switch configured to set the current detection module to operate in one of a first mode, a second mode, and a third mode, wherein:
in the first mode, the current detection module is configured to generate the digital value indicative of the first portion,
in the second mode, the current detection module is configured to generate the digital value indicative of at least the second portion when the contribution from the one or more sources other than the target source is in a first range of values, and
in the third mode, the current detection module is configured to generate the digital value indicative of at least the second portion when the contribution from the one or more sources other than the target source is in a second range of values, the second range of values having an upper end higher than an upper end of the first range of values.

2. The detection system according to claim 1 , wherein the mode switch and the target source are synchronized so that the mode switch is configured to set the current detection module to operate in the first mode when the target source is generating the contribution to the current signal, and configured to set the current detection module to operate in the second mode or in the third mode when the target source is not generating the contribution to the current signal.

3. The detection system according to claim 1 , wherein the mode switch is further configured to set the current detection module to operate in a fourth mode,
wherein in the fourth mode,
the mode switch is configured to:
set the current detection module to operate in the second mode for a first period of time while the target source is not generating the contribution to the current signal to generate a first digital value indicative of the second portion in absence of the first portion, and
set the current detection module to operate in the second mode for a second period of time while the target source is generating the contribution to the current signal to generate a second digital value indicative of a total of the first portion and the second portion, and

the current detection module is configured to generate the digital value indicative of the first portion by subtracting the first digital value from the second digital value.

4. The detection system according to claim 1 , wherein, in the second mode, the mode switch is configured to enable charge accumulation on one or more capacitive elements of the sensor for a duration of a first time interval followed by discharge of the one or more capacitive elements of the sensor to the current detection module for a duration of a second time interval thereby providing a pulsed current signal to the current detection module.

5. The detection system according to claim 4 , wherein the one or more capacitive elements of the sensor accumulate charge for a duration of a first time interval followed by discharge of the one or more capacitive elements of the sensor to the current detection module for a duration of a second time interval thereby providing a pulsed current signal to the current detection module.

6. The detection system according to claim 1 , wherein, in the third mode, the mode switch is configured to maintain charge on a capacitor of the sensor at a reference value for a duration of a first time interval followed by a second time interval during which the mode switch is configured to release maintaining of the charge on a capacitor at the reference value while enabling the capacitor of the sensor to discharge to the current detection module thereby providing a pulsed current signal to the current detection module.

7. The detection system according to claim 1 , wherein the sensor comprises one of a photosensor, a capacitance sensor, an impedance sensor, a magnetic field sensor, or a piezo-electric film.

8. The detection system according to claim 1 , wherein the contribution to the current signal from the target source comprises a pulse or a series of repeating pulses synchronized to the current detection module.

9. The detection system according to claim 1 , wherein the current detection module comprises:
a first stage comprising a trans-impedance amplifier configured to amplify the current signal and generate a low noise signal;
a second stage comprising a high pass filter configured to convert the low noise signal into an alternating current (AC) signal having a positive amplitude, a negative amplitude, and a zero cross-over point between the positive amplitude and the negative amplitude;
a third stage comprising:
a positive integrating amplifier configured to receive the positive amplitude of the AC signal and generate a positive integrated value over an integration period; and
a negative integrating amplifier configured to receive the negative amplitude of the AC signal and generate a negative integrated value over the integration period; and

a fourth stage comprising at least an analog-to-digital converter (ADC) configured to receive the positive and negative integrated values and generate the digital value indicative of the first portion of the current signal and/or the digital value indicative of the second portion of the current signal based on the positive and negative integrated values.

10. The detection system according to claim 9 , wherein the trans-impedance amplifier includes an operational amplifier with a feedback loop comprising a feedback capacitor and a feedback resistor and a low pass filter.

11. The detection system according to claim 9 , wherein the second stage includes an AC source and a capacitor that provides AC coupling.

12. The detection system according to claim 9 , wherein the third stage includes a switch configured to change from the positive integrating amplifier to the negative integrating amplifier at the occurrence of the zero cross-over point.

13. The detection system according to claim 12 , wherein the switching action of the switch is configured by a timer.

14. The detection system according to claim 13 , wherein the timer is configured to provide a clock synchronized with a frequency of the target source.

15. The detection system according to claim 9 , wherein the second stage is bypassed in the second mode and/or the third mode.

16. The detection system according to claim 9 , wherein the target source is a synchronous light source.

17. The detection system according to claim 16 , wherein a pulse of the synchronized light source has a duration of τ, a bandwidth of the second stage is approximately 1/τ, and a corner frequency of the high pass filter is set as 0.5/τ.

18. A detection system comprising:
first means for generating a current signal, the current signal comprising at least a first portion comprising a contribution from a target source and/or a second portion comprising a contribution from one or more sources other than the target source, and generating a digital value indicative of the first portion of the current signal and/or a digital value indicative of the second portion of

Assignees

• Analog Devices Inc

Inventors

• Deliwala Shrenik
• Decker Steven J
• Koker Gregory T
• Weinberg Dan M

Classifications

• G01R19/25

  using digital measurement techniques · CPC title

• G01J2001/446

  Photodiode · CPC title

• G01J1/44 Primary

  Electric circuits {(for command of an exposure part G03B7/02)} · CPC title

• G01R15/08

  Circuits for altering the measuring range · CPC title

• A61B5/02427

  Details of sensor · CPC title