Low-power receiver equalization in a clocked sense amplifier

• US 7,271,623 B2
• Filed: 12/17/2004
• Issued: 09/18/2007
• Est. Priority Date: 12/17/2004
• Status: Expired due to Fees

• Current Assignee: Rambus Inc.
• Original Assignee: Rambus Inc.
• Inventors: Palmer, Robert E.
• Primary Examiner(s): LE, DINH THANH
• Application Number:
  US11/017,477
• Publication Number:
  US 20060132191A1
• Time in Patent Office: 1,005 Days
• Field of Search: 327 50- 52, 327552-559
• US Class Current: 327/52
• CPC Class Codes: G11C 7/1078 Data input circuits, e.g. write amplifiers, data input buffers, data input registers, data input level conversion circuits
• CPC Class Codes: G11C 7/1084 Data input buffers, e.g. comprising level conversion circuits, circuits for adapting load
• CPC Class Codes: G11C 7/1087 Data input latches
• CPC Class Codes: H03F 2203/45544 the IC comprising one or more capacitors, e.g. coupling capacitors
• CPC Class Codes: H03F 3/45183 Long tailed pairs H03F3/4521, H03F3/45237 take precedence
• CPC Class Codes: H04L 25/03019 adaptive, i.e. capable of adjustment during data reception

Abstract

A receiver includes clocked, differential equalization circuitry to compensate for signal attenuation that varies with the frequency of the input signal received over a respective communication channel. The incoming signal is split into filtered and unfiltered signal components. Separate current-steering transistors coupled in parallel amplify the filtered and unfiltered components and sum the results. The filter or filters used to separate the signal components may be tunable, e.g. using voltage-controlled filter components. The ratio of device sizes for the current-steering transistors sets the magnitude of the boost applied to high-frequency components. The embodiments include adjustable or programmable current-steering networks to facilitate adjustments that accommodate the unique characteristics of individual communication channels.

Claims

1. A receiver comprising:

a. a first input terminal, a second input terminal, a first output terminal, and a second output terminal;

b. a first transistor having a first current-handling terminal coupled to the first output terminal, a second current-handling terminal, and a first control terminal coupled to the first input terminal;

c. a second transistor having a third current-handling terminal coupled to the first output terminal, a fourth current-handling terminal, and a second control terminal;

d. a first high-pass filter coupled between the first and second control terminals;

e. a third transistor having a fifth current-handling terminal coupled to the second output terminal, a sixth current-handling terminal, and a third control terminal coupled to the second input terminal;

f. a fourth transistor having a seventh current-handling terminal coupled to the second output terminal, an eighth current-handling terminal, and a fourth control terminal;

g. a second high-pass filter coupled between the third and fourth control terminals; and

h. a regenerative load having a first load input terminal coupled to the first and third current-handling terminals and a second load input terminal coupled to the fifth and seventh current-handling terminals.

2. The receiver of claim 1, further comprising a fifth transistor having a ninth current-handling terminal coupled to the second and fourth current-handling terminals, a tenth current-handling terminal, and a fifth control terminal.

3. The receiver of claim 2, further comprising a clock terminal adapted to receive a periodic clock signal, wherein the clock terminal is coupled to the fifth control terminal.

4. The receiver of claim 1, further comprising:

a. a fifth transistor having a ninth current-handling terminal coupled to the first and third current-handling terminals, a tenth current-handling terminal coupled to the fifth and seventh current-handling terminals, and a fifth control terminal; and

b. a clock terminal adapted to receive a periodic clock signal, wherein the clock terminal is coupled to the fifth control terminal.

5. The receiver of claim 1, wherein the first high-pass filter includes a capacitor coupled between the first and second control terminals.

6. The receiver of claim 1, wherein the first high-pass filter includes a resistor coupled between the second control terminal and a reference-voltage node.

7. The receiver of claim 1, further comprising a switch coupled between the first and second control terminals.

8. The receiver of claim 1, wherein the first high-pass filter is selectively, coupled between the first control terminal and the second control terminal via a first multiplexer, and wherein the second high-pass filter is selectively coupled between the third control terminal and the fourth control terminal via a second multiplexer.

9. The receiver of claim 8, wherein at least one of the first and second multiplexers includes a multiplexer input terminal coupled to a reference-voltage node.

10. The receiver of claim 9, wherein the first control terminal is selectively coupled to one of the first input terminal or the reference-voltage node via third multiplexer.

11. A receiver comprising:

a. an input terminal and an output terminal;

b. a first transistor having a first current-handling terminal coupled to the output terminal, a second current-handling terminal, and a first control terminal coupled to the input terminal;

c. a second transistor having a third current-handling terminal coupled to the output terminal, a fourth current-handling terminal, and a second control terminal;

d. a high-pass filter selectively coupled between the first and second control terminals; and

e. a switch coupled in series with the high-pass filter;

f. wherein the switch comprises a multiplexer having a first multiplexer input terminal coupled to the first control terminal, a second multiplexer input terminal coupled to a reference-voltage node, and a multiplexer output terminal coupled to the second control terminal.

12. The receiver of claim 11, wherein the first multiplexer input terminal is coupled to the first control terminal via the high-pass filter.

13. The receiver of claim 12, wherein the high-pass filter includes at least one of a tunable capacitance and a tunable resistance.

14. The receiver of claim 12, wherein the filter includes a resistor and a capacitor coupled in series between the first control terminal and the reference voltage node.

15. The receiver of claim 11, further comprising a third transistor having a fifth current-handling terminal coupled to the first and third current-handling terminals, a sixth current-handling terminal coupled to the second and fourth current-handling terminals, and a third control terminal selectively coupled to the first control terminal.

16. The receiver of claim 15, wherein the third control terminal is, when coupled to the first control terminal, capacitively coupled to the first control terminal.

17. A receiver comprising:

a. an input terminal, to receive an input signal, and an output terminal;

b. a first transistor having a first current-handling terminal coupled to the output terminal, a second current-handling terminal, and a first control terminal coupled to the input terminal to receive the input signal;

c. a high-pass filter having a filter input node, coupled to the first control terminal, and a filter output node;

d. a multiplexer having a first multiplexer input terminal coupled to the filter output node, a second multiplexer input terminal, and a multiplexer output terminal;

e. a second transistor having a third current-handling terminal coupled to the first current-handling terminal, a fourth current-handling terminal, and a second control terminal coupled to the multiplexer output terminal; and

f. a reference-voltage node coupled to the second multiplexer input terminal.

18. A circuit for adjusting a received input signal having differential first and second signal halves, the circuit comprising:

a. a first current-steering leg having;

i. a first input node to receive the first signal half;

ii. a first output node;

iii. a first tail node;

iv. first and second current-steering devices each having a first terminal coupled to the first input node, a second terminal coupled to the first output node, and a third terminal coupled to the first tail node; and

v. a first filter;

vi. wherein the first terminal of at least one of the first and second current-steering devices is coupled to the first input node via the first filter;

b. a second current-steering leg having;

i. a second input node to receive the second signal half;

ii. a second output node;

iii. a second tail node;

iv. third and fourth current-steering devices each having fourth terminal coupled to the second input node, a fifth terminal coupled to the second output node, and a sixth terminal coupled to the second tail node; and

v. a second filter;

vi. wherein the fourth terminal of at least one of the third and fourth current-steering devices is coupled to the second input node via the second filter; and

c. a regenerative load having a first load terminal coupled to the first output node and a second load terminal coupled to the second output node.

19. The circuit of claim 18, wherein the first and second tail nodes are a common tail node.

20. The circuit of claim 19, wherein the tail node is periodically coupled to a supply terminal.

21. The circuit of claim 18, wherein the first terminal of the second current-steering device and the fourth terminal of the fourth current-steering device are selectively coupled to the respective first and second filters via respective first and second multiplexers.

22. The circuit of claim 21, wherein the first terminal of the second current-steering device and the fourth terminal of the fourth current-steering device are selectively coupled to a reference-voltage node via the respective first and second multiplexers.

23. The circuit of claim 18, wherein the filters include a high-pass filter.

24. A circuit for adjusting a received input signal having differential first and second signal halves, the circuit comprising:

a. a first current-steering leg having;

i. a first input node to receive the first signal half;

ii. a first output node;

iii. a first tail node;

iv. first and second current-steering devices each having a first terminal coupled to the first input node, a second terminal coupled to the first output node, and a third terminal coupled to the first tail node; and

v. a first filter;

vi. wherein the first terminal of at least one of the first and second current-steering devices is coupled to the first input node via the first filter;

b. a second current-steering leg having;

i. a second input node to receive the second signal half;

ii. a second output node;

iii. a second tail node;

iv. third and fourth current-steering devices each having a fourth terminal coupled to the second input node, a fifth terminal coupled to the second output node, and a sixth terminal coupled to the second tail node; and

v. a second filter;

vi. wherein the fourth terminal of at least one of the third and fourth current-steering devices is coupled to the second input node via the second filter;

c. a first switch coupled between the first filter and the first current-steering device and a second switch coupled between the second filter and the third current-steering device; and

d. a regenerative load having a first load terminal coupled to the first output node and a second load terminal coupled to the second output node.

25. A system for equalizing an input signal on a respective input terminal, the system comprising:

a. a first transistor having a first current-handling terminal, a second current-handling terminal, and a first control terminal coupled to the input terminal;

b. a second transistor having a third current-handling terminal coupled to the first current-handling terminal, a fourth current-handling terminal, and a second control terminal;

c. a filter coupled between the input terminal and the second control terminal, the filter exhibiting a negative three (−

3) dB point;

d. means for tuning the −

3 dB point; and

e. means for selectively coupling the input terminal to the second control terminal via the filter.

26. A differential receiver comprising:

a. differential first and second input nodes to receive respective first and second differential signal components;

b. differential first and second output nodes;

c. a first leg including;

i. a first transistor having a first current-handling terminal coupled to the first differential output node, a second current-handling terminal, and a first control terminal coupled to the first input node;

ii. N second transistors, each having a third current-handling terminal coupled to the first differential output node, a fourth current-handling terminal, and a second control terminal; and

iii. a first filter coupled between the first input node and at least one of the second control terminals of the N second transistors;

d. a second leg including;

i. a third transistor having a first current-handling terminal coupled to the second differential output node, a second current-handling terminal, and a first control terminal coupled to the second input node;

ii. N fourth transistors, each having a third current-handling terminal coupled to the second differential output node, a fourth current-handling terminal, and a second control terminal; and

iii. a second filter coupled between the second input node and at least one of the second control terminals of the N fourth transistors;

e. a reference-voltage node; and

f. a multiplexer selectively coupling the first control terminal of the first transistor to one of the reference-voltage node and the first input node.

27. The differential receiver of claim 26, wherein the reference-voltage node conveys a common-mode reference voltage vcm.

28. The differential receiver of claim 27, further comprising a second multiplexer to selectively couple the second control terminal of at least one of the N second transistors to one of the first filter and the reference-voltage node.

29. The differential receiver of claim 26, further comprising a tail transistor coupled between a second reference-voltage node and each of the second and fourth current-handling terminals, the tail transistor including a tail control terminal.

30. The differential receiver of claim 29, further comprising a clock terminal adapted to receive a periodic clock signal, wherein the clock terminal is coupled to the tail control terminal.

31. A circuit comprising:

a. first and second input nodes to receive respective first and second signal halves;

b. first and second filters coupled to the respective first and second input nodes, the first filter to split the first input signal into a first signal portion and a filtered second signal portion, the second filter to split the second input signal into a third signal portion and a filtered fourth signal portion;

c. first and second transistors to amplify the respective first and third signal portions and to provide the resulting amplified first and third signal portions on respective first and second output nodes;

d. third and fourth transistors to amplify the respective filtered second and fourth signal portions and to provide the resulting amplified second and fourth signal portions on the respective first and second output nodes to combine with the respective amplified first and third signal portions; and

e. N additional pairs of transistors, each of the additional transistors being coupled to one of the first and second output nodes.

32. The circuit of claim 31, wherein the filters are tunable.

33. The circuit of claim 31, wherein the first and third signal portions are unfiltered.

34. The circuit of claim 31, wherein at least one transistor of the N additional pairs of transistors selectively amplifies the filtered second signal portion and at least one transistor of the N additional pairs of transistors selectively amplifies the filtered fourth signal portion.