High-frequency input circuit
View Patent ↗A high-frequency input circuit. The input circuit includes an input node, a bond pad, and a signal conversion resistor coupled in series between the input node and the bond pad to convert substantially all of a signal voltage at the input node to a signal current at the bond pad.
1. An apparatus configured to terminate a transmission line, comprising:
a current receiving differential input buffer; and
termination circuitry, coupled to the current receiving differential input buffer, wherein the termination circuitry is configured to present a resistive input impedance to an incoming signal present on the transmission line, comprising:
a first input node and a second input node of a component package, wherein the first input node and the second input node are configured to be coupled to the transmission line to receive the incoming signal;
a first bond pad and a second bond pad disposed on a die within the component package and coupled to the differential input buffer;
a first signal conversion resistor coupled in series between the first input node and the first bond pad;
a second signal conversion resistor coupled in series between the second input node and the second bond pad; and
a damping resistor coupled between the first bond pad and the second bond pad.
2. The apparatus of claim 1 , wherein the first signal conversion resistor is disposed within the component package and off of the die.
3. The apparatus of claim 1 , wherein the first signal conversion resistor is disposed outside of the component package.
4. The apparatus of claim 3 , further comprising:
a printed circuit board, wherein the component package and the first signal conversion resistor are disposed on the printed circuit board; and
a transmission trace disposed on the printed circuit board, wherein the first signal conversion resistor is coupled between the transmission trace and the component package.
5. The apparatus of claim 1 , wherein the current receiving differential input buffer comprises a trans-impedance amplifier.
6. A method for terminating a transmission line having a differential voltage impressed thereon, comprising:
providing a current receiving differential input buffer and termination circuitry, coupled to the current receiving differential input buffer, wherein the termination circuitry is configured to present a resistive input impedance to an incoming signal present on the transmission line, wherein the termination circuitry comprises a first input node and a second input node of a component package, wherein the first input node and the second input node are configured to be coupled to the transmission line, and wherein a first bond pad and a second bond pad are disposed on a die within the component package and coupled to the differential input buffer;
receiving the differential voltage between the first input node and the second input node;
converting the differential voltage to a first signal current and a second signal current via a first signal conversion resistor coupled between the first input node and the first bond pad and a second signal conversion resistor coupled between the second input node and the second bond pad, respectively;
receiving the first signal current and the second signal current from the first signal conversion resistor and a second signal conversion resistor at a first input and a second input of the differential input buffer respectively; and
damping a resonance signal received between the first input and the second input of the differential input buffer the via a damping resistor coupled therebetween.
7. The method of claim 6 , further comprising limiting a signal voltage swing across an effective input capacitance coupled to the differential input buffer.
8. The method of claim 6 , further comprising providing electrostatic discharge protection for the differential input buffer.
9. The method of claim 6 , further comprising converting substantially all of the first and second signal current into an output signal voltage usable by circuitry coupled to an output of the differential input buffer.
10. The method of claim 6 , further comprising matching a characteristic impedance of the transmission line via a matching resistor coupled between the first input node and the second input node.
11. The apparatus of claim 1 , further comprising an electrostatic discharge protection circuit coupled to the differential input buffer.
12. The apparatus of claim 1 , wherein the resistance value of the damping resistor is related to the implementation of the differential input buffer.
13. The apparatus of claim 1 , wherein the damping resistor is implemented as an on-die resistor.
14. The apparatus of claim 1 , wherein the damping resistor is integrated with the differential input buffer.
15. The apparatus of claim 1 , further comprising a matching resistor coupled between the first input node and the second input node.
16. The apparatus of claim 15 , wherein the matching resistor is configured to match a characteristic impedance of the transmission line.
17. The apparatus of claim 1 , wherein the damping resistor is configured to dampen a resonance signal received between the first input and the second input of the differential input buffer.
18. An apparatus configured to terminate a transmission line, comprising:
a current receiving differential trans-impedance amplifier; and
termination circuitry, coupled to the current receiving differential trans-impedance amplifier, wherein the termination circuitry is configured to present a resistive input impedance to an incoming signal present on the transmission line, regardless of the actual capacitance present on a bond pad that is coupled to the current receiving differential trans-impedance amplifier, comprising:
a first input node and a second input node of a component package, wherein the first input node and the second input node are configured to be coupled to the transmission line to receive the incoming signal;
a first bond pad and a second bond pad disposed on a die within the component package and coupled to the differential trans-impedance amplifier; and
a first signal conversion resistor coupled in series between the first input node and the first bond pad configured to convert substantially all of a first signal voltage of the incoming signal at the first input node to a first signal current at the first bond pad, wherein the first signal conversion resistor is configured to isolate an effective first input capacitance from a first leg of the transmission line such that the effective first input capacitance does not appear in parallel with the first signal conversion resistor;
a second signal conversion resistor coupled in series between the second input node and the second bond pad configured to convert substantially all of a second signal voltage of the incoming signal at the second input node to a second signal current at the first bond pad, wherein the second signal conversion resistor is configured to isolate an effective second input capacitance from a second leg of the transmission line such that the effective second input capacitance does not appear in parallel with the second signal conversion resistor;
a damping resistor coupled between the first bond pad and the second bond pad configured to dampen a resonance signal received between the first input and the second input of the differential input buffer; and
a matching resistor coupled between the first input node and the second input node configured to match a characteristic impedance of the transmission line.
19. The apparatus of claim 18 , further comprising an electrostatic discharge protection circuit coupled to the trans-impedance amplifier.
20. The apparatus of claim 18 , wherein the resistance value of the damping resistor is related to the implementation of the trans-impedance amplifier.