초록 ▼

An improved reference voltage (Vref) generator useable, for example, in sensing data on single-ended channels is disclosed. The Vref generator can be placed on the integrated circuit containing the receivers, or may be placed off chip. In one embodiment, the Vref generator comprises an adjustable-re

An improved reference voltage (Vref) generator useable, for example, in sensing data on single-ended channels is disclosed. The Vref generator can be placed on the integrated circuit containing the receivers, or may be placed off chip. In one embodiment, the Vref generator comprises an adjustable-resistance voltage divider in combination with a current source. The voltage divider is referenced to I/O power supplies Vddq and Vssq, with Vref being generated at a node intervening between the adjustable resistances of the voltage divider. The current source injects a current into the Vref node and into a non-varying Thevenin equivalent resistance formed of the same resistors used in the voltage divider. So constructed, the voltage generated equals the sum of two terms: a first term comprising the slope between Vref and Vddq, and a second term comprising a Vref offset. Each of these terms can be independently adjusted in first and second modes: the slope term via the voltage divider, and the offset term by the magnitude of the injected current. Use of the disclosed Vref generator in one useful implementation allows Vref to be optimized at two different values for Vddq.

대표청구항 ▼

1. A system, comprising: an adjustable current source;a reference voltage generator to generate a reference voltage at a node, the node to receive injected current from the adjustable current source, a change in a magnitude of the injected current to result in a change in a magnitude of the referenc

1. A system, comprising: an adjustable current source;a reference voltage generator to generate a reference voltage at a node, the node to receive injected current from the adjustable current source, a change in a magnitude of the injected current to result in a change in a magnitude of the reference voltage; anda first adjustable resistance and a second adjustable resistance, a first end of each of the first adjustable resistance and the second adjustable resistance coupled to the node, a second end of each of the first adjustable resistance and the second adjustable resistance being selectively coupleable to a first power supply voltage or a second power supply voltage based on a common control signal, the magnitude of the reference voltage at the node being between a magnitude of the first power supply voltage and a magnitude of the second power supply voltage. 2. The system of claim 1, wherein the adjustable current source comprises a positive current source and a negative current source. 3. The system of claim 1, wherein the adjustable current source comprises a plurality of positive current production legs coupleable to a positive current source, each of the plurality of positive current production legs being selectable to add differing amounts of current to the injected current at the node. 4. The system of claim 1, wherein the adjustable current source comprises a plurality of negative current production legs coupleable to a negative current source, each of the plurality of negative current production legs being selectable to subtract differing amounts of current to the injected current at the node. 5. The system of claim 1, wherein the adjustable current source comprises a positive current source and a negative current source, the system further comprising: a plurality of positive current production legs coupled to the positive current source, each of the plurality of positive current production legs being selectable to add differing amounts of current to the injected current at the node; anda plurality of negative current production legs coupled to the negative current source, each of the plurality of negative current production legs being selectable to subtract differing amounts of current to the injected current at the node. 6. The system of claim 5, wherein the positive current source is to produce a magnitude of current larger than current of the negative current source to provide coarse adjustment of the injected current from the plurality of positive current production legs and fine adjustment of the injected current from the plurality of negative current production legs. 7. The system of claim 5, wherein the negative current source is to produce a magnitude of current larger than current of the positive current source to provide coarse adjustment of the injected current from the plurality of negative current production legs and fine adjustment of the injected current from the plurality of positive current production legs. 8. The system of claim 1, wherein a magnitude of the reference voltage is configured to be optimized for at least different magnitudes of the first power supply voltage, the optimization being based on both a voltage margin and a timing margin at which data is sensed in a communication system. 9. The system of claim 8, wherein the communications system is a single-ended communications system. 10. The system of claim 1, wherein the second end of each of the first adjustable resistance and the second adjustable resistance is selectively coupleable by a first transistor and a second transistor to the first power supply voltage or the second power supply voltage, the common control signal being configured to be received at gates of the first transistor and the second transistor concurrently. 11. An apparatus to generate a reference voltage, the apparatus comprising: a first current source coupled on a first end to a voltage reference node; anda resistor stage comprising a plurality of resistors, each of the plurality of resistors coupled at a first end to the voltage reference node and selectably coupleable at a second end to either a first power supply voltage or a second power supply voltage. 12. The apparatus of claim 11, wherein the first current source comprises a bandgap reference circuit. 13. The apparatus of claim 11, further comprising a plurality of cascode devices each being selectable to increase an output impedance of the first current source compared to the resistor stage. 14. The apparatus of claim 11, wherein a change in a magnitude of the current injected into the node is to result in a change in a magnitude of the reference voltage. 15. The apparatus of claim 14, wherein the magnitude of the reference voltage is between the first power supply voltage and the second power supply voltage. 16. The apparatus of claim 11, wherein the first current source is adjustable. 17. The apparatus of claim 11, wherein the first current source is coupled on a second end to a third power supply voltage having a magnitude and polarity equal to or greater than the first power supply voltage. 18. The apparatus of claim 11, further comprising a second current source coupled on a first end to the voltage reference node and on a second end to a fourth power supply voltage having a magnitude and polarity equal to or less than the second power supply voltage. 19. The apparatus of claim 18, wherein a magnitude of the first current source and the second current source is independently selectable to adjust a magnitude of the reference voltage. 20. The apparatus of claim 18, wherein the first current source comprises a positive current source and the second current source comprises a negative current source to respectively add to and subtract from a magnitude of current injected into the voltage reference node. 21. The reference voltage generator of claim 11, wherein the adjustable current source is to adjust the magnitude of the reference voltage independently of the magnitudes of the first power supply voltage and the second power supply voltage. 22. An apparatus to generate a reference voltage, the apparatus comprising: an adjustable current source to inject an adjustable current into a voltage reference node; andan adjustable voltage divider coupled on a first end to the voltage reference node and couplable on a second end to either a first power supply voltage or a second power supply voltage to adjust the reference voltage, the adjustable current source being configured to adjust the reference voltage independently of the first power supply voltage and the second power supply voltage. 23. A method of producing a reference voltage, the method comprising: applying at least one power supply voltage to a reference voltage generator; andprogramming the reference voltage generator to produce, at a reference voltage node, a reference voltage value, the reference voltage node comprising a point in a voltage divider, the programming the reference voltage generator includes adjusting a value of current injected to the reference voltage node, and adjusting a value of resistance in the voltage divider.