DRAM interface circuits having enhanced skew, slew rate and impedance control
View Patent ↗Fully-buffered dual in-line memory modules (FB-DIMM) include advanced memory buffers (AMBs) having enhanced skew, slew rate and output impedance control. The AMB includes user accessible registers that can be programmed to carefully control the edge placement (or phase) of signals generated from the AMB to multiple DRAMs on the module. This control of edge placement, which may be performed independently for each group of signals: clock (CLK, CLK#), command (RAS, CAS, WE), address (including bank address), data (DQ) and data strobe (DQS), provides 360 degrees of control (or one period). This means that any group of signals can be moved independently by one complete period relatively to any other group.
1. An integrated circuit device, comprising:
a DRAM interface circuit having clock, address, command and data driver circuits therein that support independent skew control in response to respective clock, address, command and data skew control signals.
2. The device of claim 1 , wherein each of the clock, address, command and data driver circuits is responsive to a plurality of timing signals that represent multiple phases of an interface clock signal.
3. The device of claim 2 , wherein each of the clock, address, command and data driver circuits is responsive to three (or six) timing signals that are phase-offset by 120° (or 60°) relative to each other.
4. The device of claim 2 , wherein the data driver circuit is a dual data rate (DDR) driver circuit that supports 2N bits/second data rates, where N is a frequency of the interface clock signal.
5. The device of claim 2 , wherein each of the clock, address, command and data driver circuits comprises a respective phase interpolator responsive to the plurality of timing signals.
6. The device of claim 2 , wherein at least one of the clock, address, command and data driver circuits comprises an output buffer responsive to slew rate and impedance control signals.
7. The device of claim 1 , wherein at least one of the clock, address, command and data driver circuits comprises an output buffer responsive to slew rate and impedance control signals.
8. The device of claim 1 , wherein each of the clock, address, command and data driver circuits comprises an output buffer responsive to respective slew rate and impedance control signals.
9. An integrated circuit device, comprising:
a DRAM interface circuit having clock, address, command and data driver circuits therein that support independent skew, slew rate and impedance control in response to respective clock, address, command and data skew, slew rate and impedance control signals.
10. The device of claim 9 , wherein each of the clock, address, command and data driver circuits is responsive to a plurality of timing signals that represent multiple phases of an interface clock signal.
11. The device of claim 10 , wherein each of the clock, address, command and data driver circuits is responsive to three (or six) timing signals that are phase-offset by 120° (or 60°) relative to each other.
12. The device of claim 10 , wherein the data driver circuit is a dual data rate (DDR) driver circuit that supports 2N bits/second data rates, where N is a frequency of the interface clock signal.
13. A DIMM-compatible memory buffer, comprising:
a dual data rate DRAM interface circuit having clock, address, command, data and strobe driver circuits therein that support independent skew control in response to respective clock, address, command, data and strobe skew control signals.
14. The device of claim 13 , wherein each of the clock, address, command and data driver circuits is responsive to a plurality of timing signals that represent multiple phases of an interface clock signal.
15. The device of claim 14 , wherein each of the clock, address, command and data driver circuits is responsive to three (or six) timing signals that are phase-offset by 120° (or 60°) relative to each other.
16. A dual data rate DRAM interface circuit, comprising:
a clock driver circuit configured to generate an off-chip clock signal in response to an internal clock signal, a multi-bit clock skew control signal and a plurality of timing signals that represent multiple phases of an interface clock signal;
an address driver circuit configured to generate an off-chip address signal in response to an internal address signal, a multi-bit address skew control signal and the plurality of timing signals;
a command driver circuit configured to generate an off-chip command signal in response to an internal command signal, a multi-bit command skew control signal and the plurality of timing signals; and
a data driver circuit configured to generate a plurality of off-chip data signals in response to a plurality of internal data signals, a multi-bit data skew control signal and the plurality of timing signals.
17. The interface circuit of claim 16 , further comprising a strobe driver circuit configured to generate an off-chip strobe signal in response to an internal strobe signal, a multi-bit strobe skew control signal and the plurality of timing signals.
18. The interface circuit of claim 17 , wherein the plurality of timing signals represent multiple phases of an interface clock signal.
19. The interface circuit of claim 17 , wherein the plurality of timing signals is three (or six) timing signals that are phase-offset by 120° (or 60°) relative to each other.
20. The interface circuit of claim 16 , wherein at least one of said address driver circuit, command driver circuit and said data driver circuit comprises an output buffer responsive to slew rate and impedance control signals.
21. An integrated circuit device, comprising:
a DRAM interface circuit having clock and data driver circuits therein that are responsive to a plurality of phases of an interface clock signal, said clock and data driver circuits configured to support independent skew control over a full period of the interface clock signal, in response to respective clock and data skew control signals.