Selectively configurable analog signal sampler

• US 6,031,399 A
• Filed: 02/13/1998
• Issued: 02/29/2000
• Est. Priority Date: 02/13/1998
• Status: Expired due to Term

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Varma, Seema, Vu, Ha Chu
• Primary Examiner(s): TON, MY TRANG
• Application Number:
  US09/023,681
• Time in Patent Office: 746 Days
• Field of Search: 327/91, 327/93, 327/94, 327/95, 327/96, 327/554, 330/9, 341/122, 348/241, 348/250
• US Class Current: 327/96
• CPC Class Codes: G11C 27/026 associated with an amplifier G11C27/028 takes precedence

Abstract

A selectively configurable analog signal sampler, e.g., for use in an imaging system, for generating a differential sampled analog output signal which corresponds to a single-ended analog input signal with one or more signal characteristics including a positive signal polarity, a negative signal polarity, a return-to-reference signal waveform and a non-return-to-reference signal waveform. A switched capacitor matrix is configured, along with an operational amplifier with differential inputs and outputs, to allow all single-ended analog input signals with such signal characteristics to be sampled and converted to corresponding differential sampled analog output signals. Additionally, an accumulation mode of operation is provided in which the signal sampler accumulates N successive samples of the input signal and outputs the sum of such N samples, thereby allowing the signal sampler to operate at its rated speed while the circuit providing the input signal, e.g., an image sensor, operates at N-times such speed.

Claims

1. An apparatus including a selectively configurable analog signal sampler for sampling a plurality of types of analog signals, comprising:

a plurality of capacitive circuits;

an amplifier circuit coupled to said plurality of capacitive circuits; and

a plurality of switch circuits, coupled to said plurality of capacitive circuits and said amplifier circuit, configured to receive a plurality of reference signals and a plurality of switch control signals and in accordance therewith

couple together selected portions of said plurality of capacitive circuits,

couple selected portions of said plurality of reference signals to said amplifier circuit and to further selected portions of said plurality of capacitive circuits, and

couple said amplifier circuit to still further selected portions of said plurality of capacitive circuits;

wherein said plurality of capacitive circuits, said amplifier circuit and said plurality of switch circuits, together and in accordance with said plurality of reference signals and a plurality of combinations of said plurality of switch control signals, receive and couple a single-ended analog input signal to said plurality of capacitive circuits and said amplifier circuit and in accordance therewith provide a differential sampled analog output signal which corresponds to said single-ended analog input signal; and

wherein said single-ended analog input signal has one or more signal characteristics which include a positive signal polarity, a negative signal polarity, a return-to-reference signal waveform and a non-return-to-reference signal waveform.

2. The apparatus of claim 1, wherein said single-ended analog input signal includes a plurality of input signal values at an input signal rate and in accordance with one of said plurality of combinations of said plurality of switch control signals:

said differential sampled analog output signal includes a plurality of output signal values at an output signal rate which is 1/N-times said input signal rate; and

each one of said plurality of output signal values corresponds to an accumulation of N input signal values.

3. The apparatus of claim 1, wherein said plurality of switch circuits comprises a plurality of pass transistors.

4. The apparatus of claim 1, wherein said amplifier circuit comprises an operational amplifier with differential input and output terminals.

5. The apparatus of claim 4, wherein said plurality of capacitive circuits includes a plurality of feedback capacitors coupled between said differential input and output terminals.

6. The apparatus of claim 1, wherein said plurality of capacitive circuits includes an input coupling capacitor configured to receive and ac-couple said single-ended analog input signal.

7. The apparatus of claim 1, further comprising a control signal generator, coupled to said plurality of switch circuits, configured to receive and process a plurality of sample control signals and in accordance therewith provide said plurality of switch control signals.

8. An apparatus including a selectively configurable analog signal sampler for sampling a plurality of types of analog signals, comprising:

a first switching stage configured to receive a first portion of a plurality of switch control signals and in accordance therewith receive a first portion of a plurality of reference signals and receive and switch a single-ended analog input signal and in accordance therewith provide a first switched analog signal, wherein said single-ended analog input signal has one or more signal characteristics which include a positive signal polarity, a negative signal polarity, a return-to-reference signal waveform and a non-return-to-reference signal waveform;

a first capacitive stage, coupled to said first switching stage, configured to receive and capacitively couple said first switched analog signal and in accordance therewith provide a coupled analog signal;

a second switching stage, coupled to said first capacitive stage, configured to receive a second portion of said plurality of switch control signals and in accordance therewith receive a second portion of said plurality of reference signals and receive and switch said coupled analog signal and in accordance therewith provide a second switched analog signal;

a second capacitive stage, coupled to said second switching stage;

an amplifier stage, coupled to said second switching stage and said second capacitive stage; and

a third switching stage, coupled to said amplifier stage and said second capacitive stage, configured to receive a third portion of said plurality of switch control signals and in accordance therewith receive and switch a third portion of said plurality of reference signals and in accordance therewith provide a plurality of switched reference signals;

wherein said amplifier stage and said second capacitive stage together receive said second switched analog signal and said plurality of switched reference signals and in accordance therewith provide a differential sampled analog output signal which corresponds to said single-ended analog input signal.

9. The apparatus of claim 8, wherein said single-ended analog input signal includes a plurality of input signal values at an input signal rate and in accordance with a combination of said first, second and third portions of said plurality of switch control signals:

said differential sampled analog output signal includes a plurality of output signal values at an output signal rate which is 1/N-times said input signal rate; and

each one of said plurality of output signal values corresponds to an accumulation of N input signal values.

10. The apparatus of claim 8, wherein said first, second and third switching stages comprise first, second and third pluralities of pass transistors.

11. The apparatus of claim 8, wherein said amplifier stage comprises an operational amplifier with differential input and output terminals.

12. The apparatus of claim 11, wherein said second capacitive stage comprises a plurality of feedback capacitors coupled between said differential input and output terminals.

13. The apparatus of claim 8, further comprising an input capacitive stage configured to receive and ac-couple said single-ended analog input signal.

14. The apparatus of claim 8, further comprising a control signal generator, coupled to said first, second and third switching stages, configured to receive and process a plurality of sample control signals and in accordance therewith provide said plurality of switch control signals.

15. A method of sampling a plurality of types of analog signals, said method comprising the steps of:

receiving a plurality of reference signals and a plurality of switch control signals and in accordance therewith

coupling together selected portions of a plurality of capacitive circuits;

coupling selected portions of said plurality of reference signals to an amplifier circuit and to further selected portions of said plurality of capacitive circuits, and

coupling said amplifier circuit to still further selected portions of said plurality of capacitive circuits; and

in accordance with said plurality of reference signals and a plurality of combinations of said plurality of switch control signals, receiving and coupling a single-ended analog input signal to said plurality of capacitive circuits and said amplifier circuit and in accordance therewith generating a differential sampled analog output signal which corresponds to said single-ended analog input signal, wherein said single-ended analog input signal has one or more signal characteristics which include a positive signal polarity, a negative signal polarity, a return-to-reference signal waveform and a non-return-to-reference signal waveform.

16. The method of claim 15, wherein said step of receiving and coupling a single-ended analog input signal to said plurality of capacitive circuits and said amplifier circuit and in accordance therewith generating a differential sampled analog output signal which corresponds to said single-ended analog input signal comprises:

receiving a single-ended analog input signal which includes a plurality of input signal values at an input signal rate; and

in accordance with one of said plurality of combinations of said plurality of switch control signals, generating a differential sampled analog output signal which includes a plurality of output signal values at an output signal rate which is 1/N-times said input signal rate, wherein each one of said plurality of output signal values corresponds to an accumulation of N input signal values.

17. The method of claim 15, wherein said step of coupling selected portions of said plurality of reference signals to an amplifier circuit and to further selected portions of said plurality of capacitive circuits comprises coupling said selected portions of said plurality of reference signals to differential input and output terminals of an operational amplifier.

18. The method of claim 17, wherein said step of coupling said amplifier circuit to still further selected portions of said plurality of capacitive circuits comprises coupling a plurality of feedback capacitors between said differential input and output terminals.

19. The method of claim 15, wherein said step of receiving and coupling a single-ended analog input signal to said plurality of capacitive circuits and said amplifier circuit and in accordance therewith generating a differential sampled analog output signal which corresponds to said single-ended analog input signal comprises ac-coupling said single-ended analog input signal to said plurality of capacitive circuits.

20. The method of claim 15, further comprising the step of receiving and processing a plurality of sample control signals and in accordance therewith generating said plurality of switch control signals.

21. A method of sampling a plurality of types of analog signals, said method comprising the steps of:

receiving a first portion of a plurality of switch control signals and in accordance therewith receiving a first portion of a plurality of reference signals and receiving and switching a single-ended analog input signal and in accordance therewith generating a first switched analog signal, wherein said single-ended analog input signal has one or more signal characteristics which include a positive signal polarity, a negative signal polarity, a return-to-reference signal waveform and a non-return-to-reference signal waveform;

receiving and capacitively coupling said first switched analog signal and in accordance therewith generating a coupled analog signal;

receiving a second portion of said plurality of switch control signals and in accordance therewith receiving a second portion of said plurality of reference signals and receiving and switching said coupled analog signal and in accordance therewith generating a second switched analog signal;

receiving a third portion of said plurality of switch control signals and in accordance therewith receiving and switching a third portion of said plurality of reference signals and in accordance therewith generating a plurality of switched reference signals; and

receiving said second switched analog signal and said plurality of switched reference signals and in accordance therewith generating a differential sampled analog output signal which corresponds to said single-ended analog input signal.

22. The method of claim 21, wherein:

said step of receiving a first portion of a plurality of switch control signals and in accordance therewith receiving a first portion of a plurality of reference signals and receiving and switching a single-ended analog input signal and in accordance therewith generating a first switched analog signal comprises receiving a single-ended analog input signal which includes a plurality of input signal values at an input signal rate; and

said step of receiving said second switched analog signal and said plurality of switched reference signals and in accordance therewith generating a differential sampled analog output signal which corresponds to said single-ended analog input signal comprises generating, in accordance with a combination of said first, second and third portions of said plurality of switch control signals, a differential sampled analog output signal which includes a plurality of output signal values at an output signal rate which is 1/N-times said input signal rate, wherein each one of said plurality of output signal values corresponds to an accumulation of N input signal values.

23. The method of claim 21, further comprising the step of receiving and ac-coupling said single-ended analog input signal prior to said receiving and switching of said single-ended analog input signal and in accordance therewith generating said first switched analog signal.

24. The method of claim 21, further comprising the step of receiving and processing a plurality of sample control signals and in accordance therewith generating said plurality of switch control signals.