Compact high speed duty cycle corrector

Patent metadata

Field	Value
Publication number	US-10122368-B2
Application number	US-201715840984-A
Country	US
Kind code	B2
Filing date	Dec 13, 2017
Priority date	Dec 23, 2016
Publication date	Nov 6, 2018
Grant date	Nov 6, 2018

Abstract

Embodiments of the present invention provide techniques for duty cycle correction of clock signals. An input clock signal passes through a pair of output transistors, which provides an output clock signal based on the input clock signal. A duty cycle sensor generates a first correction signal based on the output clock signal. The first correction signal is at least partially opposite of the output clock signal. A duty cycle corrector generates a second correction signal based on the first correction signal. The duty cycle corrector includes two or more transistors for generating the second correction signal. The second correction signal is applied to the output clock signal. There are other embodiments as well.

First claim

What is claimed is:

1. A duty cycle correction device comprising:
an input terminal for receiving a first clock signal, the first clock signal being characterized by a first duty cycle and a signal frequency;
a first pair of transistors being configured to receive the input clock signal and output a second clock signal;
an output terminal for outputting a corrected clock signal, the output terminal being coupled to the first pair of transistors, the corrected clock signal being characterized by a second duty cycle, the second duty cycle being closer to 50% than the first duty cycle;
a duty cycle sensor coupled to the output terminal and being configured to generate a first correction signal, the first correction signal being substantially inverted relative to the input clock signal;
a digital to analog converter (DAC) being configured to generate a control voltage based on a digital control signal; and
a duty cycle corrector being configured to generate a second correction signal using at least the control voltage and the first correction signal, the second correction signal being coupled to the output terminal.

2. The device of claim 1 wherein the first pair of transistors comprises a PMOS transistor and an NMOS transistor.

3. The device of claim 1 wherein the duty cycle comprises a first inverter and a second inverter.

4. The device of claim 1 wherein the input terminal receives the first clock signal from a clock data recovery device.

5. The device of claim 1 wherein the duty cycle corrector comprises a second pair of transistors.

6. The device of claim 5 wherein the duty cycle corrector further comprises a third pair of transistors.

7. The device of claim 5 wherein the third pair of transistor is associated with a raise time and a fall time of the corrected clock signal.

8. The device of claim 5 wherein where the second pair of transistors is characterized by a smaller area than the first pair of resistors.

9. The device of claim 1 wherein the duty cycle is associated with an operating frequency, the operating frequency being lower than the signal frequency.

10. A communication system comprising:
a signal processing module being configured to equalize a data signal;
a clock data recovery (CDR) device being configured to generate a first clock signal based on the equalized data signal;
a duty cycle correction (DCC) device being configured to generate a corrected clock signal based on the first clock signal, wherein the DCC device comprises:
an input terminal for receiving the first clock signal;
a first pair of transistors being configured to receive the first clock signal via the input terminal and to output a second clock signal, the first pair transistor comprises a PMOS transistor and an NMOS transistor;
an output node being coupled to the second clock signal;
a duty cycle sensor being configured to generate a first correction signal based on the second clock signal; and
a duty cycle corrector being configured to generate a second correction signal based on the first correction signal, the second correction signal being coupled to the output node.

11. The system of claim 10 wherein the signal processing module comprises a continuous time linear equalizer.

12. The system of claim 10 wherein the signal processing module further comprises a variable gain amplifier.

13. The system of claim 10 wherein the CDR device is configured to generate four clock phases.

14. The system of claim 10 wherein the first pair of transistors comprises a PMOS transistor and an NMOS transistor.

15. The system of claim 10 wherein the DCC device further comprises a digital to analog converter (DAC) module for generating a duty cycle control voltage.

16. The system of claim 15 wherein the duty cycle corrector further comprises a second pair of transistors, the second pair of transistors being configured to generate control signals applied to the second pair of transistors.

17. The system of claim 15 wherein the DAC module is configured to convert a duty cycle control signal to the duty cycle control voltage.

18. The system of claim 10 wherein the CDR device is coupled to a divider device.

19. A method for correcting clock duty cycles, the method comprising:
processing an input clock signal using a first pair of transistors, the input clock signal being characterized by a first duty cycle;
providing an output clock signal using the first pair of transistors;
generating a first correction signal by at least inverting a portion of the output clock signal;
receiving a duty cycle control value;
converting the duty cycle control value to a control voltage;
providing a control signal by a second pair of transistors;
generating a second correction signal by a third pair of transistors using the control signal and the first correction signal, the second correction being associated with a rise or fall time; and
applying the second correction signal to the output clock signal, the output clock signal being characterized by a second duty cycle, the second duty cycle being closer to 50% than the first duty cycle.

20. The method of claim 19 further comprising determining the duty cycle control value based on the first duty cycle.

Assignees

• Inphi Corp

Inventors

• Forey Simon
• Nagulapalli Rajasekhar
• Mishra Parmanand

Classifications

• H04L27/01

  Equalisers {(baseband equalizers at the transmitter end H04L25/03343; in analogue transmission systems H04B3/04, H04B7/005)} · CPC title

• H03G3/20 Primary

  Automatic control ({H03G3/005 takes precedence;} combined with volume compression or expansion H03G7/00) · CPC title

• H03L7/0807 Primary

  concerning mainly a recovery circuit for the reference signal · CPC title

• H03K5/1565 Primary

  the output pulses having a constant duty cycle · CPC title