Method and apparatus for reducing transmitter AC-coupling droop

• US 8,570,074 B2
• Filed: 10/31/2011
• Issued: 10/29/2013
• Est. Priority Date: 08/12/2008
• Status: Active Grant

• Current Assignee: Marvell Asia Pte Limited (Marvell Technology Group Limited)
• Original Assignee: Marvell International Limited (Marvell Technology Group Limited)
• Inventors: Pagnanelli, Chris
• Primary Examiner(s): LUU, AN T
• Application Number:
  US13/285,589
• Publication Number:
  US 20120043997A1
• Time in Patent Office: 729 Days
• Field of Search: 327108-112, 327/594, 327/595
• US Class Current: 327/108
• CPC Class Codes: H04L 25/0278 Arrangements for impedance matching
• CPC Class Codes: H04L 25/0284 Arrangements to ensure DC-balance
• CPC Class Codes: H04L 25/0298 Arrangement for terminating transmission lines

Abstract

As part of a transmitter and receiver system a droop compensator is provided between the channel isolation device and the driver system to compensate for reduced transition densities. The droop compensator is configured to improve power transfer to the channel in response to reductions in transition density without affecting power transfer during periods of high transition density. The droop compensator creates an impedance mismatch between the matching circuit and driver in relation to the line impedance. The droop compensator may comprise passive elements, such as capacitors, inductors, or resistor, or active elements including transistors or power control modules. The droop compensator may be configured to operate with transformer line couplers or capacitor line couplers, and either current drivers or voltage drivers.

Claims

1. A system for reducing voltage droop, the system comprising:

a driver configured to

amplify a signal to be transmitted over a communication channel, the communication channel having a characteristic impedance, and

output the amplified signal on the communication channel;

an isolation device configured to isolate the driver from the communication channel;

a resistance configured to match the characteristic impedance of the communication channel, the resistance being connected between the driver and the isolation device; and

a voltage compensator, wherein

an electrical characteristic of the voltage compensator is selected i) to create an impedance mismatch with respect to the characteristic impedance of the communication channel, and ii) based on a desired frequency response to reduce the voltage droop, and

the voltage compensator is connected to the resistance between the driver and the isolation device.

2. The system of claim 1, wherein the voltage compensator is configured to create an impedance mismatch between i) the driver and the resistance, and ii) the characteristic impedance of the communication channel.

3. The system of claim 1, wherein the driver comprises a voltage line driver or a current line driver.

4. The system of claim 1, wherein the isolation device comprises a transformer coupling or a capacitive coupling.

5. The system of claim 1, wherein the communication channel includes a first signal line and a second signal line, and wherein the resistance comprises:

a first resistor connected in series with the first signal line between i) the driver and ii) the isolation device, and

a second resistor connected in parallel to the first resistor and in series with the second signal line between i) the driver and ii) the isolation device.

6. The system of claim 5, wherein the voltage compensator comprises:

a first capacitor connected in series between the first resistor and the isolation device; and

a second capacitor connected in series between the second resistor and the isolation device.

7. The system of claim 5, wherein the voltage compensator comprises:

a first inductor connected in parallel to the first resistor; and

a second inductor connected in parallel to the second resistor.

8. The system of claim 1, wherein the voltage compensator is configured to, in response to lower transition densities, increase an impedance looking into a signal source from the communication channel.

9. A system for reducing voltage droop, the system comprising:

a driver configured to

amplify a signal to be transmitted over a communication channel, the communication channel having a characteristic impedance, and

output the amplified signal on the communication channel;

an isolation device configured to isolate the driver from the communication channel;

a resistance configured to match the characteristic impedance of the communication channel, the resistance being connected between the driver and the isolation device; and

a voltage compensator, wherein

an electrical characteristic of the voltage compensator is selected i) to create an impedance mismatch with respect to the characteristic impedance of the communication channel, and ii) based on a desired frequency response to reduce the voltage droop,

the voltage compensator is connected to the resistance between the driver and the isolation device, and

the communication channel includes a first signal line and a second signal line, and wherein

the resistance comprises

a first resistor connected i) between the first signal line and the second signal line, and ii) between the driver and the isolation device, and

a second resistor connected in series with the first resistor between the first signal line and the second signal line, and

the voltage compensator comprises

a first capacitor connected in series with the first resistor and the second resistor, and

a second capacitor connected in series with the first capacitor, the first resistor, and the second resistor.

10. A system for reducing voltage droop, the system comprising:

a driver configured to

amplify a signal to be transmitted over a communication channel, the communication channel having a characteristic impedance, and

output the amplified signal on the communication channel;

an isolation device configured to isolate the driver from the communication channel;

a resistance configured to match the characteristic impedance of the communication channel, the resistance being connected between the driver and the isolation device; and

a voltage compensator, wherein

an electrical characteristic of the voltage compensator is selected i) to create an impedance mismatch with respect to the characteristic impedance of the communication channel, and ii) based on a desired frequency response to reduce the voltage droop,

the voltage compensator is connected to the resistance between the driver and the isolation device, and

the communication channel includes a first signal line and a second signal line, and wherein

the resistance comprises a first resistor connected i) between the first signal line and the second signal line, and ii) between the driver and the isolation device, and

the voltage compensator comprises an inductor connected i) in parallel to the first resistor, ii) between the first signal line and the second signal line, and iii) between the first resistor and the isolation device.

11. A method for reducing voltage droop, the method comprising:

using a driver,

amplifying a signal to be transmitted over a communication channel, the communication channel having a characteristic impedance, and

outputting the signal on the communication channel; and

isolating the driver from the communication channel using an isolation device,

wherein a resistance is connected between the driver and the isolation device, the resistance being configured to match the characteristic impedance of the communication channel, and

wherein

a voltage compensator is connected to the resistance between the driver and the isolation device, and

an electrical characteristic of the voltage compensator is selected i) to create an impedance mismatch with respect to the characteristic impedance, and ii) based on a desired frequency response to reduce the voltage droop.

12. The method of claim 11, further comprising:

using the voltage compensator, creating an impedance mismatch between i) the driver and the resistance, and ii) the characteristic impedance.

13. The method of claim 11, wherein the driver comprises a voltage line driver or a current line driver.

14. The method of claim 11, wherein the isolation device comprises a transformer coupling or a capacitive coupling.

15. The method of claim 11, wherein the communication channel includes a first signal line and a second signal line, and wherein the resistance comprises:

a first resistor connected in series with the first signal line between i) the driver and ii) the isolation device; and

a second resistor connected in parallel to the first resistor and in series with the second signal line between i) the driver and ii) the isolation device.

16. The method of claim 15, wherein the voltage compensator comprises:

a first capacitor connected in series between the first resistor and the isolation device; and

a second capacitor connected in series between the second resistor and the isolation device.

17. The method of claim 15, wherein the voltage compensator comprises:

a first inductor connected in parallel to the first resistor; and

a second inductor connected in parallel to the second resistor.

18. The method of claim 11, further comprising:

in response to lower transition densities, using the voltage compensator to increase an impedance looking into a signal source from the communication channel.

19. A method for reducing voltage droop, the method comprising:

using a driver,

amplifying a signal to be transmitted over a communication channel, the communication channel having a characteristic impedance, and

outputting the signal on the communication channel; and

isolating the driver from the communication channel using an isolation device,

wherein a resistance is connected between the driver and the isolation device, the resistance being configured to match the characteristic impedance of the communication channel,

wherein

a voltage compensator is connected to the resistance between the driver and the isolation device, and

an electrical characteristic of the voltage compensator is selected i) to create an impedance mismatch with respect to the characteristic impedance, and ii) based on a desired frequency response to reduce the voltage droop, and

the communication channel includes a first signal line and a second signal line, and wherein;

the resistance comprises

a first resistor connected i) between the first signal line and the second signal line, and ii) between the driver and the isolation device, and

a second resistor connected in series with the first resistor between the first signal line and the second signal line, and

the voltage compensator comprises

a first capacitor connected in series with the first resistor and the second resistor, and

a second capacitor connected in series with the first capacitor, the first resistor, and the second resistor.

20. A method for reducing voltage droop, the method comprising:

using a driver,

amplifying a signal to be transmitted over a communication channel, the communication channel having a characteristic impedance, and

outputting the signal on the communication channel; and

isolating the driver from the communication channel using an isolation device,

wherein a resistance is connected between the driver and the isolation device, the resistance being configured to match the characteristic impedance of the communication channel,

wherein

a voltage compensator is connected to the resistance between the driver and the isolation device, and

an electrical characteristic of the voltage compensator is selected i) to create an impedance mismatch with respect to the characteristic impedance, and ii) based on a desired frequency response to reduce the voltage droop, and

the communication channel includes a first signal line and a second signal line, and wherein

the resistance comprises a first resistor connected i) between the first signal line and the second signal line, and ii) between the driver and the isolation device, and

the voltage compensator comprises an inductor connected i) in parallel to the first resistor, ii) between the first signal line and the second signal line, and iii) between the first resistor and the isolation device.