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US 7,525,360 B1Granted
I/O duty cycle and skew control
AssigneeAltera Corporation
InventorsXiaobao Wang, Chiakang Sung, Khai Nguyen
Life of this patent
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Abstract
Circuits, methods and apparatus are provided to control the duty cycle of a signal. The rising and falling edges of a signal can be delayed independently to provide the selection or tuning of the duty cycle of the signal. Additionally, the delays can be used to reduce skew among both edges of signals being provided or transmitted by a data interface. The delays can be made to not cause a high-Z during a transition of the signal.
Claims20
An integrated circuit comprising a duty cycle control circuit, the duty cycle control circuit comprising:
- an input line coupled with a first input of a signal selection circuit;
- a delay chain having an input coupled with the input line and having an output coupled with a second input of the signal selection circuit;
- a first logic having a first input coupled with the input line and having an output coupled with a third input of the signal selection circuit, wherein the first logic is used in delaying only the rising edges of a signal on the input line;
- and
- a second logic having a first input coupled with the input line and having an output coupled with a fourth input of the signal selection circuit, wherein the second logic is used in delaying only the falling edges of the signal on the input line.
2 more elements
A method of delaying a signal, the method comprising:
- transmitting a first signal to a first input of a signal selection circuit;
- delaying both rising and falling edges of the first signal to form a second signal;
- transmitting the second signal to a second input of the signal selection circuit;
- delaying only the rising edges of the first signal to form a third signal;
- transmitting the third signal to a third input of the signal selection circuit;
- delaying only the falling edges of the first signal to form a fourth signal;
- transmitting the fourth signal to a fourth input of the signal selection circuit;
- and
- selecting one of the four signals to output from the signal selection circuit.
6 more elements
Dependencies are inferred from the claim text.