Methods, circuits and devices for improving crossover performance and/or monotonicity, and applications of the same in a universal serial bus (USB) low speed output driver

• US 5,905,389 A
• Filed: 09/22/1997
• Issued: 05/18/1999
• Est. Priority Date: 09/22/1997
• Status: Expired due to Term

• Current Assignee: Monterey Research, LLC (Vector Capital Corporation)
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Alleven, Gary W.
• Primary Examiner(s): Callahan, Timothy P.
• Assistant Examiner(s): LAM, TUAN THIEU
• Application Number:
  US08/934,805
• Time in Patent Office: 603 Days
• Field of Search: 327/77-81, 327/170, 327/108, 327/112, 327/392, 327/398, 327/399, 327/379, 327/384, 327/389, 327/391, 327/538, 327/543, 326/27, 326/82, 326/83, 326/86, 326/31, 326/26
• US Class Current: 327/108
• CPC Class Codes: H03K 19/00323 Delay compensation
• CPC Class Codes: H03K 19/00361 in field effect transistor circuits

Abstract

A circuit comprising a first driver circuit, a second driver circuit and a delay circuit. The first driver circuit may be configured to generate a first output signal and a control signal in response to a first input signal. The delay circuit may be configured to generate a delay signal in response to a second input signal and the control signal. The second driver circuit may be configured to generate a second output signal in response to the delay signal.

Claims

1. A circuit comprising:

a comparator circuit configured to present a first control signal in response to (i) a reference voltage and (ii) an input signal;

a compensation circuit configured to present a current in response to said first control signal; and

a driver circuit configured to present an output signal in response to (i) said current and (ii) said input signal.

2. The circuit according to claim 1, wherein said driver circuit comprises a pull-up device and a pull-down device.

3. The circuit according to claim 1, further comprising:

an enable circuit configured to turn off said compensation circuit after a predetermined time in response to said first control signal.

4. The circuit according to claim 1, wherein said reference voltage comprises a voltage representing a logic level of said output signal.

5. The circuit according to claim 1, wherein said reference voltage is programmable.

6. The circuit according to claim 1, wherein said compensation circuit comprises a switch coupled between said output signal and said current, wherein said switch disconnects said current from said output signal in response to said first control signal.

7. The circuit according to claim 6, wherein said switch comprises a transistor.

8. A Universal Serial Bus driver comprising the circuit of claim 1.

9. A circuit comprising:

means for generating a first control signal in response to (i) a reference voltage and (ii) an input signal;

means for generating a current in response to said first control signal; and

means for generating an output signal in response to (i) said current and (ii) said input signal, comprising a pull-up device and a pull-down device.

10. The circuit according to claim 9, further comprising:

means for generating a second control signal in response to said first control signal, wherein said second control signal decouples said means for generating said current after a predetermined time.

11. The circuit according to claim 9, wherein said reference voltage comprises a voltage representing a logic level of said output signal.

12. The circuit according to claim 9, wherein said reference voltage is programmable.

13. The circuit according to claim 9, wherein said means for generating said current further comprises means for disconnecting said current from said output signal in response to said first control signal.

14. The circuit according to claim 13, wherein said means for disconnecting comprises a transistor.

15. A Universal Serial Bus Driver comprising the circuit of claim 9.

16. A method for reducing discontinuities in an output signal comprising the steps of:

(a) generating a control signal in response to (i) a reference voltage and (ii) an input signal;

(b) generating a current in response to said control signal; and

(c) generating an output signal from at least one of a pull-up device and a pull-down device in response to (i) said current and (ii) said input signal.

17. The method according to claim 16, wherein step (b) further comprises enabling said current in response to an enabling signal.