Methods and apparatus for an interface
Various embodiments of the present technology may provide methods and apparatus for an interface. The interface may be configured as a low-voltage, bi-directional channel redriver having a transmitter and a receiver that share input pads and output pads. The interface may provide for selective biasing of the transmitter and receiver using a switching circuit and a resistance circuit connected to the channel's input and output pads.
1. An interface circuit, comprising:
a receiver connected to a transmitter;
a first pair of I/O pads connected to:
an input of the receiver;
an output of the transmitter; and
a first resistance circuit;
a second pair of I/O pads connected to:
an output of the receiver;
an input of the transmitter; and
a second resistance circuit; and
at least one switching circuit connected to one of the first and second resistance circuits;
wherein the at least one switching circuit is connected to a plurality of voltages.
2. The interface circuit according to claim 1 , wherein each of the first and second resistance circuits comprises a plurality of resistors.
3. The interface circuit according to claim 1 , wherein each of the first and second switching circuits comprises a plurality of switching devices.
4. The interface circuit according to claim 1 , wherein:
the first resistance circuit is directly connected to:
a first I/O pad from the first pair of I/O pads; and
a second I/O pad from the first pair of I/O pads; and
the second resistance circuit is directly connected to:
a first I/O pad from the second pair of I/O pads; and
a second I/O pad from the second pair of I/O pads.
5. The interface circuit according to claim 1 , wherein each voltage from the plurality of voltages is less than 3.0 volts.
6. The interface circuit according to claim 1 , further comprising:
a first switching circuit connected to the first pair of I/O pads via the first resistance circuit; and
a second switching circuit connected to the second pair of I/O pads via the second resistance circuit;
wherein each switching circuit is:
connected to the plurality of voltages; and
selectively operable to apply:
a first voltage to the first pair of I/O pads; and
a second voltage to the second pair of I/O pads.
7. The interface circuit according to claim 6 , wherein:
the first switching circuit is configured to selectively connect a first voltage from the plurality of voltages to the first pair of I/O pads via the first resistance circuit; and
the second switching circuit is configured to selectively connect a second voltage from the plurality of voltages to the second pair of I/O pads via the second resistance circuit;
wherein the second voltage is different from the first voltage.
8. The interface circuit according to claim 7 , wherein:
the first resistance circuit comprises:
a first resistive element connected between a second I/O pad from the first pair of I/O pads and the first switching circuit; and
a second resistive element connected between a first I/O pad from the first pair of I/O pads and the first switching circuit; and
the second resistance circuit comprises:
a third resistive element connected between a first I/O pad from the second pair of I/O pads and the second switching circuit; and
a fourth resistive element connected between a second I/O pad from the second pair of I/O pads and the second switching circuit.
9. The interface circuit according to claim 1 , wherein:
the first resistance circuit comprises:
a first resistive element directly connected to a second I/O pad from the first pair of I/O pads; and
a second resistive element directly connected to a first I/O pad from the first pair of I/O pads; and
the second resistance circuit comprises:
a third resistive element directly connected to a first I/O pad from the second pair of I/O pads; and
a fourth resistive element directly connected to a second I/O pad from the second pair of I/O pads.
10. A method for operating an interface circuit, comprising:
during a first mode:
applying a first voltage to a first pair of I/O pads via a first resistance circuit;
applying a second voltage to a second pair of I/O pads via a second resistance circuit, wherein the second voltage is different from the first voltage; and
during a second mode:
applying the second voltage to the first pair of I/O pads via the first resistance circuit; and
applying the second voltage to the second pair of I/O pads via the second resistance circuit;
wherein:
the first resistance circuit comprises:
a first resistive element connected to a second I/O pad from the first pair of I/O pads; and
a second resistive element connected to a first I/O pad from the first pair of I/O pads; and
the second resistance circuit comprises:
a third resistive element connected to a first I/O pad from the second pair of I/O pads; and
a fourth resistive element connected to a second I/O pad from the second pair of I/O pads.
11. The method according to claim 10 , wherein applying the first voltage to the first pair of I/O pads comprises selectivity operating a first switching device connected to the first resistance circuit.
12. The method according to claim 10 , wherein applying the second voltage to the second pair of I/O pads comprises selectively operating a second switching device connected to the second resistance circuit.
13. The method according to claim 10 , wherein the interface is configured as a bi-directional channel comprising a transmitter connected to and in parallel with a receiver.
14. The method according to claim 10 , wherein the first and second voltages are less than 3.0 volts.
15. The method according to claim 10 , wherein the interface is configured as a uni-directional channel comprising one of: a transmitter and a receiver.
16. A system, comprising:
a host device connected to a sink device via an interface circuit, wherein the interface circuit comprises:
a bi-directional channel comprising:
a receiver;
a transmitter connected to the receiver;
a first pair of I/O pads shared by an input of the receiver and an output of the transmitter; and
a second pair of I/O pads shared by an output of the receiver and an input of the transmitter;
a first resistance circuit connected to the first pair of I/O pads;
a first switching circuit connected to the first resistance circuit and configured to selectively apply a first voltage to the first pair of I/O pads;
a second resistance circuit connected to the second pair of I/O pads; and
a second switching circuit connected to the second resistance circuit and configured to selectively apply a second voltage, which is different from the first voltage, to the second pair of I/O pads.
17. The system according to claim 16 , wherein:
the first resistance circuit comprises:
a first resistive element directly connected to a second I/O pad from the at least one pair of I/O pads; and
a second resistive element directly connected to a first I/O pad from the at least one pair of I/O pads.
18. The system according to claim 16 , wherein:
the first switching circuit is connected to a plurality of voltages;
the first switching device comprises a plurality of switching devices; and
each switching device from the plurality of switching devices connects one voltage from the plurality of voltages to the first resistance circuit.
19. The system according to claim 16 , wherein the host device is connected to the interface circuit via a first transmission line; and the sink device is connected to the interface via a second transmission line.