Two-step analog-digital converting circuit and method

Patent metadata

Field	Value
Publication number	US-8952314-B2
Application number	US-201213616205-A
Country	US
Kind code	B2
Filing date	Sep 14, 2012
Priority date	Oct 19, 2011
Publication date	Feb 10, 2015
Grant date	Feb 10, 2015

Abstract

A two-step analog-digital converting circuit includes a comparator, an upper bit counter and a pulse residue conversion unit. The comparator is configured to compare a ramp signal and an input signal, and to output a resulting comparative signal. The upper bit counter is configured to receive the comparative signal and a clock signal, and to output upper bit values corresponding to a first time interval between a generation time point of the ramp signal and a first edge of the clock signal, the first edge of the clock signal immediately preceding a state transition time point of the comparative signal. The pulse residue conversion unit is configured to receive the comparative signal and the clock signal, and to output lower bit values corresponding to a second time interval between the first edge of the clock signal and the state transition time point of the comparative signal.

First claim

What is claimed is:

1. A two-step analog-digital converting circuit comprising:
a comparator configured to compare a ramp signal and an input signal, and to output a resulting comparative signal;
an upper bit counter configured to receive the comparative signal and a clock signal, and to output upper bit values corresponding to a first time interval between a generation time point of the ramp signal and a first edge of the clock signal, the first edge of the clock signal immediately preceding a state transition time point of the comparative signal; and
a pulse residue conversion unit configured to receive the comparative signal and the clock signal, and to output lower bit values corresponding to a second time interval between the first edge of the clock signal and the state transition time point of the comparative signal.

2. The two-step analog-digital converting circuit of claim 1 , wherein the pulse residue conversion unit comprises:
a voltage generation circuit configured to output a voltage proportional to a third time interval between the state transition time point of the comparative signal and a second edge of the clock signal, the second edge of the clock signal immediately following the state transition time point; and
an analog-digital converter configured to convert the voltage into digital bits and to output the digital bits as the lower bit values.

3. The two-step analog-digital converting circuit of claim 2 , wherein the analog-digital converter comprises one of a flash analog-digital converter (ADC), a successive approximation ADC, an algorithmic ADC, or a pipelined ADC.

4. The two-step analog-digital converting circuit of claim 2 , wherein the voltage generation circuit comprises:
a pulse generator configured to output a pulse corresponding to the third time interval; and
a voltage generator configured to output the voltage proportional to a width of the pulse.

5. The two-step analog-digital converting circuit of claim 4 , wherein the pulse generator comprises a flip-flop.

6. The two-step analog-digital converting circuit of claim 4 , wherein the voltage generator comprises a current-voltage converter configured to convert a reference current into the voltage in response to the pulse.

7. The two-step analog-digital converting circuit of claim 6 , wherein the voltage generator comprises:
a reference current source configured to generate the reference current;
a capacitor;
a switch configured to control connection between the reference current source and the capacitor; and
a buffer configured to buffer a voltage of the capacitor and to output the buffered voltage as the voltage.

8. The two-step analog-digital converting circuit of claim 1 , wherein the upper bit values and the lower bit values are output successively.

9. An image sensor comprising:
the two-step analog-digital converting circuit of claim 1 ;
a ramp signal generator configured to generate the ramp signal; and
a pixel configured to convert an optical signal into an electric signal and to provide the electric signal to the two-step analog-digital converting circuit as the input signal.

10. The image sensor of claim 9 , wherein the pulse residue conversion unit comprises:
a pulse generator configured to output a pulse corresponding to a third time interval between the state transition time point and a second edge of the clock signal, the second edge of the clock signal immediately following the state transition time point
a current-voltage converter configured to convert a reference current into a voltage in response to the pulse; and
an analog-digital converter configured to convert the voltage into digital bits and to output the digital bits as the lower bit values.

11. An image processing apparatus comprising:
the image sensor of claim 9 ; and
a processor configured to control the operation of the image sensor.

12. A two-step analog-digital converting method, comprising:
comparing a ramp signal and an input signal with each other and outputting a comparative signal;
outputting upper bit values corresponding to a count value of a first time interval between a generation time point of the ramp signal and a first edge of a clock signal, the first edge of the clock signal being immediately previous to a state transition time point of the comparative signal; and
outputting lower bit values corresponding to a second time interval between the first edge of the clock signal and the state transition time point of the comparative signal.

13. The method of claim 12 , wherein outputting the lower bit values comprises:
generating a voltage proportional to a third time interval between the state transition time point and a second edge of the clock signal, the second edge of the clock signal being immediately after the state transition time point; and
converting the voltage into digital bits and outputting the digital bits as the lower bit values.

14. The method of claim 13 , wherein generating the voltage comprises:
generating a pulse having a pulse width corresponding to the third time interval; and
generating the voltage changing according to the pulse width.

15. The method of claim 12 , wherein the upper bit values and the lower bit values are output successively.

16. An analog-digital converting circuit comprising:
a comparator configured to compare a ramp signal and an input signal, and to output a resulting comparative signal;
an upper bit counter configured to receive the comparative signal and to output upper bit values corresponding to a first time interval between a generation time point of the ramp signal and a first edge of the clock signal immediately preceding a state transition time point of the comparative signal, wherein the state transition time point of the comparative signal does not coincide with an edge of a clock signal; and
a pulse residue conversion unit configured to receive the comparative signal and to output lower bit values corresponding to a second time interval between the first edge of the clock signal and the state transition time point of the comparative signal.

17. The analog-digital converting circuit of claim 16 , wherein the pulse residue conversion unit comprises:
a voltage generation circuit configured to output a voltage proportional to a third time interval between the state transition time point of the comparative signal and a second edge of the clock signal immediately following the state transition time point; and
an analog-digital converter configured to convert the voltage into the lower bit values.

18. The analog-digital converting circuit of claim 2 , wherein the voltage generation circuit comprises:
a pulse generator configured to output a pulse having pulse width corresponding to the third time interval; and
a voltage generator configured to output the voltage proportional to the pulse width.

19. The analog-digital converting circuit of claim 18 , wherein the pulse generator comprises a flip-flop.

20. The analog-digital converting circuit of claim 19 , wherein the voltage generator comprises:
a reference current source configured to generate the reference current;
a capacitor; and
a switch configured to connect the reference current source to the capacitor in response to the pulse having a high level and to disconnect the reference current source from the capacitor in response to the pulse having a low level, wherein a voltage of the capacitor corresponds to the voltage output by the voltage generator.

Assignees

• Park Yu Jin
• Yoo Kwi Sung
• Lim Seung Hyun
• Samsung Electronics Co Ltd

Inventors

• Park Yu Jin
• Yoo Kwi Sung
• Lim Seung Hyun

Classifications

• H03M1/123

  Simultaneous, i.e. using one converter per channel but with common control or reference circuits for multiple converters · CPC title

• H04N25/767

  Horizontal readout lines, multiplexers or registers · CPC title

• H03M1/16 Primary

  with scale factor modification, i.e. by changing the amplification between the steps {(H03M1/141 takes precedence)} · CPC title

• H04N25/76

  Addressed sensors, e.g. MOS or CMOS sensors · CPC title

• H03M1/56

  Input signal compared with linear ramp · CPC title