High speed differential signal detection

• US 6,727,732 B1
• Filed: 09/18/2002
• Issued: 04/27/2004
• Est. Priority Date: 09/18/2002
• Status: Active Grant

• Current Assignee: Intersil Corporation (Renesas Electronics Corporation)
• Original Assignee: BitBlitz Communications, Inc. (Renesas Electronics Corporation)
• Inventors: Wu, Bin, Rana, Manoj N.
• Primary Examiner(s): Wells, Kenneth B.
• Application Number:
  US10/246,982
• Time in Patent Office: 587 Days
• Field of Search: 327/108-112, 327/63-67, 327/89, 327/170
• US Class Current: 327/65
• CPC Class Codes: H03K 5/082 with an adaptive threshold
• CPC Class Codes: H03K 5/19 Monitoring patterns of pulse trains indicating amplitude G01R19/00; indicating frequency G01R23/00; measuring characteristics of individual pulses G01R29/02

Abstract

A method and a circuit detect the presence of a high-speed signal, such as a high-speed differential signal, based on a software-programmable signal amplitude threshold. In one embodiment, when the amplitude threshold is exceeded, a current is generated to charge a capacitor. The voltage on the capacitor is compared to a second pre-set voltage in a low-speed comparator, which provides an output voltage indicating detection of the high-speed signal.

Claims

1. A differential signal detection circuit, comprising:

a capacitor; and

a detection circuit receiving (a) a differential signal comprising a first component signal and a second component signal, and (b) a threshold voltage, said detection circuit charging said capacitor when one of said component signals of said differential signal has an amplitude exceeding said threshold voltage by a predetermined amount.

2. A differential signal detection circuit as in claim 1, further comprising a comparator receiving a reference voltage and coupled to said capacitor, said comparator providing an output signal having two binary states, said output signal transitioning between said binary states when a voltage on said capacitor exceeds said reference voltage.

3. A differential signal detection circuit as in claim 1, wherein said detection circuit comprises first and second transistors each having a source terminal and a drain terminal being coupled respectively to a terminal of said capacitor and a predetermined voltage, and a gate terminal coupled to one of said component signals of said differential signal.

4. A differential signal detection circuit as in claim 2, wherein said reference voltage is generated by tapping a string of resistors.

5. A differential signal detection circuit as in claim 4, wherein a second reference voltage is generated from said string of resistors, said reference voltage being selected by activating one of a plurality of switches.

6. A differential signal detection circuit as in claim 5, wherein said switches are software programmable.

7. A method for detecting a differential signal, comprising:

receiving a differential signal comprising a first component signal and a second component signal;

receiving a threshold voltage; and

charging a capacitor when one of said component signals of said signal has an amplitude exceeding said threshold voltage by a predetermined amount.

8. A method for detecting said differential signal as in claim 7, further comprising receiving a reference voltage and receiving a voltage of said capacitor;

and providing an output signal having two binary states, said output signal transitioning between said binary states when said voltage on said capacitor exceeds said reference voltage.

9. A method for detecting a differential signal as in claim 7, further comprising providing first and second transistors each having a source terminal and a drain terminal being coupled respectively to a terminal of said capacitor and a predetermined voltage, and a gate terminal coupled to one of said component signals of said differential signal.

10. A method for detecting a differential signal as in claim 8, further comprising generating said reference voltage by tapping a string of resistors.

11. A method for detecting a differential signal as in claim 10, further comprising generating a second reference voltage from said string of resistors, said reference voltage being selected by activating one of a plurality of switches.

12. A method for detecting a differential signal as in claim 11, further comprising programming said switches by software.