High-speed programmable frequency divider with 50% output duty cycle
First Claim
1. An integrated circuit device comprising:
- a multiplexer having a first input terminal coupled to receive a first integer value (M) and a second input terminal for receiving a second integer value that is M plus a least significant bit (LSB), the multiplexer configured to alternately output M and the second integer value;
a multi-modulus divider coupled to the multiplexer for receiving the output of the multiplexer and having a clock input for receiving a clock signal, the multi-modulus divider operable to alternately generate an output pulse at M input clock cycles and at M+LSB clock cycles;
a divide-by-two counter having an input coupled to the output of the multi-modulus divider, the divide-by-two counter operable to divide the output of the multi-modulus divider to generate a divided clock signal having a frequency equal to 2M+LSB; and
duty cycle correction logic coupled to the output of the divide by two counter, the duty cycle correction logic configured to correct the duty cycle of the divided clock signal to a fifty percent duty cycle when the LSB is odd.
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Accused Products
Abstract
A frequency divider includes a multiplexer having a first input terminal coupled to receive a first value M and a second input terminal for receiving a second value that is M+LSB, the multiplexer is configured to alternately output the first value M and the second value. The frequency divider includes a multi-modulus divider coupled to the multiplexer for receiving the output of the multiplexer, the multi-modulus divider operable to alternately generate an output pulse at M input clock cycles and at M+LSB clock cycles. A divide-by-two counter having an input coupled to the output of the multi-modulus divider, is operable to divide the output of the multi-modulus divider to generate a divided clock signal having a frequency of N, where N is equal to 2M+LSB. Duty cycle correction logic is coupled to the output of the divide-by-two counter and is configured to correct the duty cycle of the divided clock signal to a fifty percent duty cycle when N is odd.
119 Citations
18 Claims
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1. An integrated circuit device comprising:
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a multiplexer having a first input terminal coupled to receive a first integer value (M) and a second input terminal for receiving a second integer value that is M plus a least significant bit (LSB), the multiplexer configured to alternately output M and the second integer value; a multi-modulus divider coupled to the multiplexer for receiving the output of the multiplexer and having a clock input for receiving a clock signal, the multi-modulus divider operable to alternately generate an output pulse at M input clock cycles and at M+LSB clock cycles; a divide-by-two counter having an input coupled to the output of the multi-modulus divider, the divide-by-two counter operable to divide the output of the multi-modulus divider to generate a divided clock signal having a frequency equal to 2M+LSB; and duty cycle correction logic coupled to the output of the divide by two counter, the duty cycle correction logic configured to correct the duty cycle of the divided clock signal to a fifty percent duty cycle when the LSB is odd. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method comprising:
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alternately dividing an input clock signal by a first divisor having a first integer value (M) M and a second divisor having a value of M plus a least significant bit (LSB) to alternate periodically between generating an output pulse at M input clock cycles and M+LSB input clock cycles; dividing the generated output pulse using a divide-by-two counter to generate a divided clock signal having a frequency equal to 2M+LSB; and correcting the duty cycle of the divided clock signal when the LSB is odd to generate a corrected divided clock signal having a fifty percent duty cycle. - View Dependent Claims (10, 11)
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12. A frequency divider comprising:
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an adder having a first input for receiving a first integer value (M) and a second input for receiving a least significant bit (LSB), the adder operable to generate a second integer value at the output of the adder that is the sum of M and the LSB; a multiplexer having a first input terminal coupled to receive M and having a second input terminal electrically coupled to the output of the adder for receiving the second integer value, the multiplexer configured to alternately output M and the second integer value; a multi-modulus divider coupled to the multiplexer for receiving the output of the multiplexer and having a clock input for receiving a clock signal, the multi-modulus divider operable to alternately generate an output pulse at M input clock cycles and at M+LSB clock cycles; a divide-by-two counter having an input coupled to the output of the multi-modulus divider, the divide-by-two counter operable to divide the output of the multi-modulus divider to generate a divided clock signal having a frequency equal to 2M+LSB; and duty cycle correction logic coupled to the output of the divide by two counter, the duty cycle correction logic configured to correct the duty cycle of the divided clock signal to a fifty percent duty cycle when the LSB is odd. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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Specification