Transmitting apparatus with source termination

Patent metadata

Field	Value
Publication number	US-9871516-B2
Application number	US-201414296377-A
Country	US
Kind code	B2
Filing date	Jun 4, 2014
Priority date	Jun 4, 2014
Publication date	Jan 16, 2018
Grant date	Jan 16, 2018

Abstract

In one embodiment, an apparatus for transmitting a signal with an improved termination is disclosed. The apparatus includes a driver to generate a differential mode signal superimposed on a common mode signal at a differential driver output of the driver. The differential driver output includes a first driver output and a second driver output. The apparatus also includes a termination circuit coupled between the first driver output and the second driver output. The termination circuit includes a capacitor connected to a node. The termination circuit also includes a first resistor and a first inductive element coupled in series between the first driver output and the node. In addition, the termination circuit includes a second resistor and a second inductive element coupled in series between the second driver output and the node.

First claim

What is claimed is:

1. A transmitting apparatus comprising:
a transmitter driver to generate a differential mode signal superimposed on a common mode signal at a differential driver output of the transmitter driver, the differential driver output including a first driver output and a second driver output;
a common mode choke to suppress common mode noise at the differential driver output; and
a termination circuit at the differential driver output and being separate from the transmitter driver, the termination circuit coupled between the first driver output and the second driver output, the termination circuit comprising:
a capacitor connected to a node;
a first series circuit comprising a first resistor and a first inductive element coupled in series, one end of the first series circuit coupled to the node; and
a second series circuit comprising a second resistor and a second inductive element coupled in series, one end of the second series circuit coupled to the node, the first driver output connected to a first input of the common mode choke and another end of the first series circuit, while the second driver output is connected to a second input of the common mode choke and another end of the second series circuit, the first inductive element and the second inductive element causing peaking in the differential mode signal at the differential driver output,

wherein the first inductive element has an inductance L, the first resistor has a resistance R, and the common mode signal has a frequency fcm, wherein the inductance L, the resistance R and the frequency fcm satisfy the following equation:

L
<

R

2
×
π
×
fcm
×
3

.

2. The transmitting apparatus of claim 1 ,
wherein the differential mode signal and the common mode signal operate at different frequencies.

3. The transmitting apparatus of claim 2 , further comprising:
a first switch separate from the transmitter driver and coupled in series with the first resistor and the first inductive element between the first driver output and the node; and
a second switch separate from the transmitter driver and coupled in series with the second resistor and the second inductive element between the second driver output and the node.

4. The transmitting apparatus of claim 3 , wherein the first switch and second switch are closed when the apparatus is communicating through a first communication protocol, and the first switch and the second switch are open when the apparatus is communicating through a second communication protocol.

5. The transmitting apparatus of claim 3 , wherein the first switch and the second switch are on an integrated circuit with the transmitter driver.

6. The transmitting apparatus of claim 2 , wherein the first inductive element and the second inductive element are on a printed circuit board.

7. The transmitting apparatus of claim 2 , wherein the first inductive element and the second inductive element are on an integrated circuit with the transmitter driver.

8. The transmitting apparatus of claim 7 , wherein the first inductive element and the second inductive element are bonding wires.

9. The transmitting apparatus of claim 2 , wherein the first resistor and the second resistor are on a printed circuit board.

10. The transmitting apparatus of claim 2 , wherein the first resistor and the second resistor are on an integrated circuit with the transmitter driver.

11. The transmitting apparatus of claim 2 , wherein the capacitor is on a printed circuit board.

12. The transmitting apparatus of claim 2 , wherein the capacitor is on an integrated circuit with the transmitter driver.

13. The transmitting apparatus of claim 2 , wherein the differential mode signal is a mobile high definition link signal.

14. The transmitting apparatus of claim 2 , wherein the capacitor is connected between the node and ground.

15. The transmitting apparatus of claim 2 , wherein the first inductive element and the second inductive element have impedances at a frequency of the differential mode signal that causes the peaking, and the first inductive element and the second inductive element have substantially no impedance at a frequency of the common mode signal.

16. An apparatus comprising:
a driver to generate a differential mode signal superimposed on a common mode signal at a differential driver output of the driver, the differential driver output including a first driver output and a second driver output; and
a termination circuit coupled between the first driver output and the second driver output, the termination circuit comprising:
a capacitor connected to a node;
a first resistor and a first inductive element coupled in series between the first driver output and the node; and

a second resistor and a second inductive element coupled in series between the second driver output and the node, the first inductive element and the second inductive element causing peaking in the differential mode signal at the differential driver outputwherein the first inductive element has an inductance substantially equal to

L
=

1

4
×
π
×
fx

⁢

x
2

⁡

(
150
)

2

-

(
100
)

2

1
-

x
2

,

 where an insertion loss of a channel without the termination circuit is substantially equal to an insertion loss of the termination circuit at a frequency fx, and x is an insertion loss of the termination circuit at the frequency fx, wherein the channel comprises a connection to a port coupled to the first driver output and the second driver output.

17. The apparatus of claim 16 , wherein a combined loss of the insertion loss of the channel and the insertion loss of the termination circuit is between −3 dB and −4 dB at the frequency fx.

18. The transmitting apparatus

Assignees

• Lattice Semiconductor Corp

Inventors

• Jeong Youchul
• Lee Junwoo
• Lee Inyeol
• Sung Baegin

Classifications

• H03K19/0005 Primary

  Modifications of input or output impedance · CPC title

• H03K19/00346

  Modifications for eliminating interference or parasitic voltages or currents · CPC title