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US 7,135,925 B2Granted
Adaptive bias scheme for high-voltage compliance in serial links
AssigneeRambus Inc.
InventorJohn W. Poulton
Life of this patent
Estimating the term…
Abstract
A high-speed serial-link driver transmits a differential data signal to a conventional differential receiver via a differential channel. The driver employs termination voltages that are high, relative to the supply voltage employed by the transmitter core logic, to support communication with legacy devices. Cascode amplifiers using an adaptive biasing scheme allow the driver to include voltage-sensitive, high-performance transistors despite the relatively high termination voltage.
Claims21
A circuit comprising:
- a. first and second power-supply terminals;
- b. first and second cascode amplifiers, each cascode amplifier including an input terminal, a cascode terminal, a first current-handling terminal, and a second current-handling terminal;
- c. a first load coupled between the first current-handling terminal of the first cascode amplifier and the first power-supply terminal;
- d. a second load coupled between the first current-handling terminal of the second cascode amplifier and the first power-supply terminal;
- e. a first resistor coupled between the first current-handling terminal of the first cascode amplifier and the cascode terminals of the first and second cascode amplifiers;
- and
- f. a second resistor coupled between the first current-handling terminal of the second cascode amplifier and the cascode terminals of the first and second cascode amplifiers;
- g. wherein each of the first and second cascode amplifiers includes a plurality of transistors formed in common wells, and wherein the wells are electrically insulated from the first and second power-supply terminals.
5 more elements
A circuit comprising:
- a. first and second power-supply terminals;
- b. first and second cascode amplifiers, each cascode amplifier including an input terminal, a cascode terminal, a first current-handling terminal, and a second current-handling terminal;
- c. a first load coupled between the first current-handling terminal of the first cascode amplifier and the first power-supply terminal;
- d. a second load coupled between the first current-handling terminal of the second cascode amplifier and the first power-supply terminal;
- e. a first resistor coupled between the first current-handling terminal of the first cascode amplifier and the cascode terminals of the first and second cascode amplifiers;
- and
- f. a second resistor coupled between the first current-handling terminal of the second cascode amplifier and the cascode terminals of the first and second cascode amplifiers;
- g. wherein the first and second resistors exhibit resistances substantially higher than the first and second loads.
5 more elements
A circuit comprising:
- a. first and second power-supply terminals;
- b. first and second cascode amplifiers, each cascode amplifier including an input terminal, a cascode terminal, a first current-handling terminal, and a second current-handling terminal;
- c. a first load coupled between the first current-handling terminal of the first cascode amplifier and the first power-supply terminal;
- d. a second load coupled between the first current-handling terminal of the second cascode amplifier and the first power-supply terminal;
- e. a first resistor coupled between the first current-handling terminal of the first cascode amplifier and the cascode terminals of the first and second cascode amplifiers;
- and
- f. a second resistor coupled between the first current-handling terminal of the second cascode amplifier and the cascode terminals of the first and second cascode amplifiers;
- g. wherein the first and second power-supply terminals receive between them a supply voltage of a supply amplitude, and wherein the first and second cascode amplifiers receive a differential input signal having a differential amplitude substantially less then the supply amplitude.
5 more elements
A circuit comprising:
- a. first and second power-supply terminals;
- b. first and second cascode amplifiers, each cascode amplifier including an input terminal, a cascode terminal, a first current-handling terminal, and a second current-handling terminal;
- c. a first load coupled between the first current-handling terminal of the first cascode amplifier and the first power-supply terminal;
- d. a second load coupled between the first current-handling terminal of the second cascode amplifier and the first power-supply terminal;
- e. a first resistor coupled between the first current-handling terminal of the first cascode amplifier and the cascode terminals of the first and second cascode amplifiers;
- f. a second resistor coupled between the first current-handling terminal of the second cascode amplifier and the cascode terminals of the first and second cascode amplifiers;
- and
- g. a reference terminal and a third resistor coupled between the cascode terminal and the reference terminal.
5 more elements
A communication system comprising:
- a. a transmitter having:
- i. a first supply terminal to provide a termination voltage;
- ii. a second supply terminal to provide a second voltage;
- iii. first and second cascode amplifiers, each cascode amplifier including an input terminal, a cascode terminal, a first current-handling terminal, and a second current-handling terminal;
- iv. a first termination element coupled between the first current-handling terminal of the first cascode amplifier and the first supply terminal;
- v. a second termination element coupled between the first current-handling terminal of the second cascode amplifier and the first supply terminal;
- vi. a first resistor coupled between the first current-handling terminal of the first cascode amplifier and the cascode terminals of the first and second cascode amplifiers;
- and
- vii. a second resistor coupled between the first current-handling terminal of the second cascode amplifier and the cascode terminals of the first and second cascode amplifiers;
- b. a communication channel coupled to first supply terminal via the first and second termination elements;
- and
- c. a receiver coupled to the communication channel;
- d. wherein the transmitter further has a third supply terminal providing a third supply voltage lower than the first supply voltage.
10 more elements
A communication system comprising:
- a. a transmitter having:
- i. a first supply terminal to provide a termination voltage;
- ii. a second supply terminal to provide a second voltage;
- iii. first and second cascode amplifiers, each cascode amplifier including an input terminal, a cascode terminal, a first current-handling terminal, and a second current-handling terminal;
- iv. a first termination element coupled between the first current-handling terminal of the first cascode amplifier and the first supply terminal;
- v. a second termination element coupled between the first current-handling terminal of the second cascode amplifier and the first supply terminal;
- vi. a first resistor coupled between the first current-handling terminal of the first cascode amplifier and the cascode terminals of the first and second cascode amplifiers;
- and
- vii. a second resistor coupled between the first current-handling terminal of the second cascode amplifier and the cascode terminals of the first and second cascode amplifiers;
- b. a communication channel coupled to first supply terminal via the first and second termination elements;
- and
- c. a receiver coupled to the communication channel;
- d. wherein the first and second resistors exhibit resistances substantially higher than the first and second loads.
10 more elements
A communication system comprising;
- a. a transmitter having:
- i. a first supply terminal to provide a termination voltage;
- ii. a second supply terminal to provide a second voltage;
- iii. first and second cascode amplifiers, each cascode amplifier including an input terminal, a cascode terminal, a first current-handling terminal, and a second current-handling terminal;
- iv. a first termination element coupled between the first current-handling terminal of the first cascode amplifier and the first supply terminal;
- v. a second termination element coupled between the first current-handling terminal of the second cascode amplifier and the first supply terminal;
- vi. a first resistor coupled between the first current-handling terminal of the first cascode amplifier and the cascode terminals of the first and second cascode amplifiers;
- and
- vii. a second resistor coupled between the first current-handling terminal of the second cascode amplifier and the cascode terminals of the first and second cascode amplifiers;
- b. a communication channel coupled to first supply terminal via the first and second termination elements;
- and
- c. a receiver coupled to the communication channel;
- d. a reference terminal and a third resistor coupled between the cascode terminal and the reference terminal.
10 more elements
A computer-readable medium having stored thereon a data structure defining a differential driver, the data structure comprising:
- a. first data representing a first supply terminal to provide a termination voltage and a second supply terminal to provide a second voltage;
- b. second data representing first and second cascode amplifiers, each cascode amplifier including an input terminal, a cascode terminal, a first current-handling terminal, and a second current-handling terminal;
- c. third data representing a first termination element coupled between the first current-handling terminal of the first cascode amplifier and the first supply terminal, and a second termination element coupled between the first current-handling terminal of the second cascode amplifier and the first supply terminal;
- and
- d. fourth data representing a first resistor coupled between the first current-handling terminal of the first cascode amplifier and the cascode terminals of the first and second cascode amplifiers, and a second resistor coupled between the first current-handling terminal of the second cascode amplifier and the cascode terminals of the first and second cascode amplifiers;
- e. wherein the data structure further comprises fifth data representing a reference terminal and a third resistor coupled between the cascode terminal and the reference terminal.
3 more elements
Dependencies are inferred from the claim text.