LATCH STRUCTURE, FREQUENCY DIVIDER, AND METHODS FOR OPERATING SAME

• US 20100073027A1
• Filed: 09/02/2009
• Published: 03/25/2010
• Est. Priority Date: 09/19/2008
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Barnett, Kenneth, Zhang, Kun
• Granted Patent: US 8,058,901 B2
• Time in Patent Office: Days
• US Class Current: 326/68
• CPC Class Codes: H03K 23/544 with a base which is an odd number
• CPC Class Codes: H03K 3/356121 with synchronous operation H03K3/35613, H03K3/356147 take precedence
• CPC Class Codes: H03K 5/1565 the output pulses having a constant duty cycle

Abstract

A latch includes three circuits. The first circuit drives a first output (QB) to a first level when a first input (D) and a first clock phase (CK) are both low, to a second level when D and CK are both high, and provides high impedance (HI-Z) when different logic levels are applied to D and CK. The second circuit drives a second output (Q) to the first level when a third input (DB) and a complimentary clock phase (CKB) are both low, to the second level when DB and CKB are both high, and provides HI-Z when different logic levels are applied to DB and CKB. The third circuit maintains voltages of Q and QB when the first and second circuits provide HI-Z at Q and QB. Odd-number dividers constructed with such latches produce 50% duty cycle operation without restricting output pulse widths to integer multiples of input periods.

Claims

1. An electronic latch comprising:

a first circuit configured to drive a first output to a first output logic level when a first input is at a first input logic level and a second input is at the first input logic level, drive the first output to a second output logic level different from the first output logic level when the first input is at a second input logic level and the second input is at the second input logic level, and set the first output to a high impedance state when different input logic levels are applied to the first input and to the second input;

a second circuit configured to drive a second output to the first output logic level when a third input is at the first input logic level and a fourth input is at the first input logic level, drive the second output to the second output logic level when the third input is at the second input logic level and the fourth input is at the second input logic level, and set the second output to the high impedance state when different input logic levels are applied to the third input and to the fourth input; and

a third circuit configured to maintain voltage levels of the first and second outputs when the first circuit drives the first output to the high impedance state, and the second circuit drives the second output to the high impedance state.

2. The electronic latch of claim 1, wherein:

the first output logic level is a logic low;

the second output logic level is a logic high;

the first input logic level is the logic high; and

the second input logic level is the logic low.

3. The electronic latch of claim 1, wherein the third circuit comprises a pair of cross-coupled inverters.

4. The electronic latch of claim 3, wherein:

the first circuit comprises a first transistor, a second transistor, a third transistor, and a fourth transistor, the first, second, third, and fourth transistors being connected in series, each of the first, second, third, and fourth transistors comprising a drain, a source, and a gate, the first input being coupled to the gate of the second transistor and to the gate of the third transistor, the first output being coupled to the drain of the second transistor and to the drain of the third transistor; and

the second circuit comprises a fifth transistor, a sixth transistor, a seventh transistor, and an eighth transistor, the fifth, sixth, seventh, and eighth transistors being connected in series, each of the fifth, sixth, seventh, and eighth transistors comprising a drain, a source, and a gate, the third input being coupled to the gate of the sixth transistor and to the gate of the seventh transistor, the second output being coupled to the drain of the sixth transistor and to the drain of the seventh transistor.

5. The electronic latch of claim 4, wherein the third circuit comprises a pair of cross-coupled inverters.

6. The electronic latch of claim 4, wherein:

the third circuit comprises a ninth transistor, a tenth transistor, an eleventh transistor, and a twelfth transistor, each transistor of the ninth, tenth, eleventh, and twelfth transistors comprising a gate, a source, and a drain;

the drain of the ninth transistor is coupled to the drain of the tenth transistor, the gate of the eleventh transistor, the gate of the twelfth transistor, and the first output; and

the drain of the eleventh transistor is coupled to the drain of the twelfth transistor, the gate of the ninth transistor, the gate of the tenth transistor, and the second output.

7. A frequency divider comprising a plurality of latches, each latch of the plurality of latches being in accordance with claim 1, the frequency divider being configured to divide by an odd integer.

8. A frequency generator comprising the frequency divider of claim 7.

9. A wireless communication device comprising the frequency generator of claim 8.

10. A mobile communication device comprising the frequency generator of claim 8.

13. The electronic latch of claim 10, wherein:

the means for driving the first output comprises a first plurality of N-channel transistors;

the means for driving the second output comprises a second plurality of N-channel transistors; and

the means for maintaining voltage level comprises a third plurality of N-channel transistors.

11. An electronic latch comprising:

a means for driving a first output to a first output level when a first input is at a first input level and a second input is at the first input level, driving the first output to a second output level different from the first output level when the first input is at a second input level and the second input is at the second input level, and setting the first output to a high impedance state when different input levels are applied to the first input and to the second input;

a means for driving a second output to the first output level when a third input is at the first input level and a fourth input is at the first input level, driving the second output to the second output level when the third input is at the second input level and the fourth input is at the second input level, and setting the second output to the high impedance state when different input levels are applied to the third input and to the fourth input; and

a means for maintaining voltage level of the first and second outputs when the means for driving the first output drives the first output to the high impedance state, and the means for driving the second output drives the second output to the high impedance state.

12. The electronic latch of claim 11, wherein:

the first output level is a logic low;

the second output level is a logic high;

the first input level is the logic high; and

the second input level is the logic low.

14. The electronic latch of claim 11, wherein:

the means for driving the first output comprises a first plurality of P-channel transistors;

the means for driving the second output comprises a second plurality of P-channel transistors; and

the means for maintaining voltage level comprises a third plurality of P-channel transistors.

15. The electronic latch of claim 11 configured to operate between a positive supply voltage and ground potential.

16. The electronic latch of claim 11 configured to operate between a negative supply voltage and ground potential.

17. A wireless communication device comprising a frequency generator, the frequency generator comprising a frequency divider configured to divide by an odd integer, the frequency divider comprising a plurality of latches, each latch of the plurality of latches being in accordance with claim 11.

18. A frequency divider comprising a plurality of latches, each latch of the plurality of latches being configured selectively to switch state on both rising and falling edges of a clock.

19. The frequency divider of claim 18, wherein the plurality of latches is configured to divide frequency of the clock by an odd number to obtain at least one output with a duty cycle equal substantially to fifty percent.

20. A wireless device comprising a radio frequency section, the radio frequency section comprising the frequency divider of claim 19.

21. The frequency divider of claim 18, wherein the odd number is three.

22. The frequency divider of claim 18, wherein the odd number is five.

23. The frequency divider of claim 18, wherein the odd number is greater than five.

24. A method of operating an electronic latch, the method comprising:

driving a first output with a first output logic level in response to a first input and a first clock phase being at a first input logic level;

driving a second output with the first output logic level in response to a second input and a second clock phase being at the first input logic level;

driving the first output with a second output logic level in response to the first input and the first clock phase being at a second input logic level;

driving the second output with the second output logic level in response to the second input and the second clock phase being at the second input logic level;

providing a high impedance at the first output in response to the first input and the first clock phase being at different input logic levels;

providing the high impedance at the second output in response to the second input and the second clock phase being at different input logic levels; and

maintaining logic levels of the first and second outputs when the first input and the first clock phase are at different input logic levels, and the second input and the second clock phase are at different input logic levels.

25. The method of claim 24, wherein:

the second input is complement of the first input; and

the second clock phase is complement of the first clock phase.

26. The method of claim 25, wherein:

the first output logic level is a logic low;

the second output logic level is a logic high;

the first input logic level is the logic high; and

the second input logic level is the logic low.