Divider circuit

• US 8,278,974 B2
• Filed: 04/01/2011
• Issued: 10/02/2012
• Est. Priority Date: 04/09/2010
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Takahashi, Kei, Ito, Yoshiaki
• Primary Examiner(s): Nguyen, Hai L
• Application Number:
  US13/078,219
• Publication Number:
  US 20110249786A1
• Time in Patent Office: 550 Days
• Field of Search: 327/48, 327/115, 327/117, 327/118, 377/47, 377/48
• US Class Current: 327/115
• CPC Class Codes: G06F 1/06 Clock generators producing several clock signals G06F1/08 - G06F1/14 take precedence
• CPC Class Codes: H03K 21/12 with parallel read-out
• CPC Class Codes: H03K 21/406 Synchronisation of counters
• CPC Class Codes: H03K 23/54 Ring counters, i.e. feedback shift register counters H03K23/52 takes precedence

Abstract

A divider circuit includes a shift register which generates 2X (X is a natural number greater than or equal to 2) pulse signals in accordance with a first clock signal or a second clock signal and outputs them, and a divided signal output circuit which generates a signal to be a third clock signal with a cycle X times longer than a cycle of the first clock signal in accordance with the 2X pulse signals and outputs it. The divided signal output circuit includes X first transistors which control whether voltage of the signal to be the third clock signal is set to first voltage; and X second transistors which control whether voltage of the signal to be the third clock signal is set to second voltage.

Claims

1. A divider circuit comprising:

a shift register configured to output 2X pulse signals in accordance with a first clock signal and a second clock signal, wherein X is a natural number greater than or equal to 2; and

a divided signal output circuit configured to output a third clock signal with a cycle X times longer than a cycle of the first clock signal in accordance with the 2X pulse signals,

wherein the divided signal output circuit comprises;

X first transistors each having a source, a drain, and a gate,

wherein the shift register is configured to separately supply the respective gates of the X first transistors with the first to X-th pulse signals among the 2X pulse signals, and

wherein the X first transistors are configured to control whether voltage of a signal to be the third clock signal is set to first voltage; and

X second transistors each having a source, a drain, and a gate,

wherein the shift register is configured to separately supply the respective gates of the X second transistors with (X+1)-th to 2X-th pulse signals among the 2X pulse signals, and

wherein the X second transistors are configured to control whether voltage of a signal to be the third clock signal is set to second voltage.

2. The divider circuit according to claim 1,

wherein the shift register comprises sequential circuits of 2X stages,

wherein sequential circuits of odd-numbered stage in the 2X stages each comprise a third transistor which controls whether voltage of a pulse signal is set to voltage having a value depending on the first clock signal, and

wherein sequential circuits of even-numbered stage in the 2X stages each comprise a fourth transistor which controls whether the voltage of a pulse signal is set to voltage having a value depending on the second clock signal.

3. The divider circuit according to claim 1,

wherein a value of voltage of at least part of the 2X pulse signals is higher than or equal to power supply voltage.

4. The divider circuit according to claim 1,

wherein the X first transistors and the X second transistors each comprise an oxide semiconductor layer serving as a channel formation layer, and

wherein a band gap of the oxide semiconductor layer is 2 eV or more.

5. The divider circuit according to claim 1,

wherein the first clock signal and the second clock signal are clock signals whose waveforms are different from each other by a ½

cycle.

6. A clock signal generation circuit comprising:

an oscillator; and

the divider circuit according to claim 1.

7. A divider circuit comprising:

a first unit divider circuit configured to generate a third clock signal in accordance with a first clock signal and a second clock signal, wherein a cycle of the third clock signal is X times longer than a cycle of the first clock signal, and wherein X is a natural number greater than or equal to 2; and

a second unit divider circuit configured to generate a fourth clock signal in accordance with the third clock signal, wherein a cycle of the fourth clock signal is a cycle K times longer than the cycle of the third clock signal, and wherein K is a natural number greater than or equal to 2,

wherein the first unit divider circuit comprises;

a shift register configured to output 2X pulse signals in accordance with the first clock signal and the second clock signal; and

a divided signal output circuit configured to output the third clock signal in accordance with the 2X pulse signals,

wherein the divided signal output circuit comprises;

X first transistors each having a source, a drain, and a gate,

wherein the shift register is configured to separately supply the respective gates of the X first transistors with the first to X-th pulse signals among the 2X pulse signals, and

wherein the X first transistors are configured to control whether voltage of a signal to be the third clock signal is set to first voltage; and

X second transistors each having a source, a drain, and a gate,

wherein the shift register is configured to separately supply the respective gates of the X second transistors with (X+1)-th to 2X-th pulse signals among the 2X pulse signals, and

wherein the X second transistors are configured to control whether voltage of a signal to be the third clock signal is set to second voltage.

8. The divider circuit according to claim 7,

wherein the shift register comprises sequential circuits of 2X stages,

wherein sequential circuits of odd-numbered stage in the 2X stages each comprise a third transistor which controls whether voltage of a pulse signal is set to voltage having a value depending on the first clock signal, and

wherein sequential circuits of even-numbered stage in the 2X stages each comprise a fourth transistor which controls whether the voltage of a pulse signal is set to voltage having a value depending on the second clock signal.

9. The divider circuit according to claim 7,

wherein a value of voltage of at least part of the 2X pulse signals is higher than or equal to power supply voltage.

10. The divider circuit according to claim 7,

wherein the X first transistors and the X second transistors each comprise an oxide semiconductor layer serving as a channel formation layer, and

wherein a band gap of the oxide semiconductor layer is 2 eV or more.

11. The divider circuit according to claim 7,

wherein the first clock signal and the second clock signal are clock signals whose waveforms are different from each other by a ½

cycle.

12. A clock signal generation circuit comprising:

an oscillator; and

the divider circuit according to claim 7.

13. A divider circuit comprising:

a shift register configured to output a plurality of pulse signals comprising a first pulse signal, a second pulse signal, a third pulse signal, and a fourth pulse signal in accordance with a first clock signal and a second clock signal; and

a divided signal output circuit configured to output a third clock signal with a cycle X times longer than a cycle of the first clock signal in accordance with the plurality of pulse signals, wherein X is a natural number greater than or equal to 2,

wherein the divided signal output circuit comprises;

a plurality of first transistors configured to control whether voltage of a signal to be the third clock signal is set to first voltage, the plurality of first transistors comprising at least two transistors; and

a plurality of second transistors configured to control whether voltage of a signal to be the third clock signal is set to second voltage, the plurality of second transistors comprising at least two transistors,

wherein the shift register is configured to supply a gate of one of the two transistors comprised in the plurality of first transistors with one of the first pulse signal and the second pulse signal,

wherein the shift register is configured to supply a gate of the other of the two transistors comprised in the plurality of first transistors with the other of the first pulse signal and the second pulse signal,

wherein the shift register is configured to supply a gate of one of the two transistors comprised in the plurality of second transistors with one of the third pulse signal and the fourth pulse signal, and

wherein the shift register is configured to supply a gate of the other of the two transistors comprised in the plurality of second transistors with the other of the third pulse signal and the fourth pulse signal.

14. The divider circuit according to claim 13,

wherein the plurality of pulse signals comprise 2X pulse signals.

15. The divider circuit according to claim 14,

wherein the plurality of first transistors comprise X transistors, and

wherein the plurality of second transistors comprise X transistors.

16. The divider circuit according to claim 13,

wherein the plurality of first transistors and the plurality of second transistors each comprise an oxide semiconductor layer serving as a channel formation layer, and

wherein a band gap of the oxide semiconductor layer is 2 eV or more.

17. The divider circuit according to claim 13,

wherein the shift register comprises sequential circuits of 2X stages,

wherein sequential circuits of odd-numbered stage in the 2X stages each comprise a third transistor which controls whether voltage of a pulse signal is set to voltage having a value depending on the first clock signal, and

wherein sequential circuits of even-numbered stage in the 2X stages each comprise a fourth transistor which controls whether the voltage of a pulse signal is set to voltage having a value depending on the second clock signal.

18. The divider circuit according to claim 13,

wherein a value of voltage of at least part of the 2X pulse signals is higher than or equal to power supply voltage.

19. The divider circuit according to claim 13,

wherein the first clock signal and the second clock signal are clock signals whose waveforms are different from each other by a ½

cycle.

20. A clock signal generation circuit comprising:

an oscillator; and

the divider circuit according to claim 13.