Connection and disconnection differential surge limiter circuit for AC coupled transceiver

Patent metadata

Field	Value
Publication number	US-10901443-B2
Application number	US-201815946620-A
Country	US
Kind code	B2
Filing date	Apr 5, 2018
Priority date	Jan 3, 2018
Publication date	Jan 26, 2021
Grant date	Jan 26, 2021

Abstract

Disclosed herein are embodiments of a scalable connection and disconnection differential surge limiter circuit that may be utilized in any AC-coupled transceiver. Charge is recycled between PADP and PADN using two diode paths, hence protecting the PAD connected devices from voltage stress. The circuit can act as a protection circuit to limit the voltage on PADP and PADN during differential voltage spikes.

First claim

What is claimed is:

1. A surge limiter circuit comprising:
at least a first and second charge recycling circuits, each coupled between a first port and a second port;
at least a first resistor divider network having a supply terminal, a ground terminal and a divider terminal, the divider terminal coupled to the first port; and
at least a second resistor divider network having a supply terminal, a ground terminal and a divider terminal, the divider terminal coupled to the second port;
wherein a first and second diodes conduct a first small current, when there is no external connection to the first and second ports, such that a first voltage at the first port is determined by a ratio of a resistance of the first resistor divider, and wherein the first and second diode conduct the first current during a surge event to maintain the first voltage between the first port with respect to the second port at less than a first predetermined voltage; and
a third and fourth diodes conduct a second small current, when there is no external connection to the first and second ports, such that a second voltage at the second port is determined by a ratio of a resistance of the second resistor divider, and wherein the third and fourth diode conduct the second current during a surge event to maintain the second voltage between the second port with respect to the first port less than a second predetermined voltage.

2. The surge limiter circuit of claim 1 , wherein the supply terminals of the first and second resistor divider networks are coupled to a voltage source and a ground terminals of the first and second resistor divider are coupled to a ground.

3. The surge limiter circuit of claim 1 , wherein the first predetermined voltage is equal to a sum of a forward bias diode drop of the first and second diodes and the second predetermined voltage is equal to the sum of the forward bias diode drop of the third and fourth diodes.

4. The surge limiter circuit of claim 1 , wherein a voltage at a divider terminal is one half a voltage source.

5. The surge limiter circuit of claim 4 , wherein the resistance in the first resistor divider network between the supply terminal and the divider terminal is approximately 600,000 Ohms and between the ground terminal and the divider terminal is approximately 600,000 Ohms.

6. The surge limiter circuit of claim 5 , wherein the resistance in the second resistor divider network between the supply terminal and the divider terminal is approximately 600,000 Ohms and between the ground terminal and the divider terminal is approximately 600,000 Ohms.

7. The surge limiter circuit of claim 4 further including:
a first switch placed between the supply terminal of the first resistor divider network and the voltage source;
a second switch placed between the ground terminal of the first resistor divider network and ground
a third switch placed between the supply terminal of the second resistor divider network and the voltage source; and
a fourth switch placed between the ground terminal of the second resistor divider network and ground.

8. The surge limiter circuit of claim 7 , wherein the first, second, third and fourth switches each have a control input to allow the switches to be controlled by a resistor divider control signal.

9. The surge limiter circuit of claim 8 , wherein the control inputs to the first, second, third, and fourth switches receive one control signal that operates all of the switches together.

10. The surge limiter circuit of claim 9 , wherein at least one of the first, second, third, and fourth switches are transistors.

11. The surge limiter circuit of claim 9 , wherein at least one of the first, second, third, and fourth switches is a field effect transistor (FET).

12. The surge limiter circuit of claim 9 , wherein:
the first charge recycling circuit includes a first and second diodes, each having a cathode and an anode, the cathode of the first diode coupled to the first port, the anode of the first diode being coupled to the cathode of the second diode and the anode of the second diode being coupled to the second port;
the second charge recycling circuit includes a third and fourth diodes, each having a cathode and an anode, the anode of the third diode coupled to the first port and the cathode of the third diode being coupled to the anode of the fourth diode and the cathode of the fourth diode being coupled to the second port.

13. The surge limiter circuit of claim 12 , wherein the voltage of the second port with respect to the first port is maintained less than a sum of a forward biased diode drop of the first and second diodes and wherein the voltage of the first port with respect to the second port is less than the sum of the forward biased diode drop of the third diode with the fourth diode.

14. The surge limiter circuit of claim 12 , further including the first switch coupled between the anode of the first diode and the cathode of the second diode and the second switch coupled between the cathode of the third diode and the anode of the fourth diode.

15. The surge limiter circuit of claim 8 , wherein the control inputs of at least the first and second switches receives a first control signal that operates both switches together and the third and fourth switch receives a second control signal that operates both switches together.

16. A surge limiter circuit, including:
a first port;
a second port;
a first diode having a cathode connected to the first port;
a second diode having an anode connected to the first port;
a third diode having cathode connected to the anode of the first diode and having an anode connected to the second port;
a fourth diode having an anode connected to the cathode of the second diode and a cathode connected to the second port;
a first weak resistive divider including:
a first divider terminal coupled to a voltage source and to a first terminal of a first resistance,
a second divider terminal coupled to a ground and to ft first terminal of a second resistance; and
a third divider terminal coupled to a second terminal of the first resistance, a second terminal of the second resistance and to the first port; and
a second weak resistive divider including:
a fourth divider terminal coupled to the voltage source and to a first terminal of a third resistance;
a fifth divider terminal coupled to ground and to a first terminal of a fourth resistance; and
a sixth divider terminal coupled to a second terminal of the third resistance, the second terminal of the fourth resistance and to the second port.

Assignees

• Synopsys Inc

Inventors

• Kumar Daljeet

Classifications

• H04B3/02 Primary

  Details · CPC title

• H02H9/005

  avoiding undesired transient conditions · CPC title

• H01C1/16

  Resistor networks not otherwise provided for · CPC title

• H03K17/0822

  in field-effect transistor switches · CPC title

• G05F1/569 Primary

  for protection · CPC title