US Patents Granted

Circuits, methods, and apparatus for transmitting, receiving, aligning and re-synchronizing high-speed single-ended signals by aligning a clock signal to one or more received data signals. A receiver amplifier circuit senses and captures low swing single ended signals at the receiver. Alignment is done on a per pin basis where a clock signal is distributed and independently phase shifted and aligned to each incoming data signal. In one example, a preamble containing a training data pattern is transmitted. The receiver steps through a number of dynamic timing alignment codes, each of which selects a different phase-shifted clock signal. The received data is examined for errors and the optimal clock signal is selected. Periodic dynamic readjustments of multiple clock alignment circuits may be made to compensate for temperature and voltage drift and variations.

Circuits, methods, and apparatus that provide accurate on-chip termination impedances for high-speed data interface circuits. One embodiment of the present invention provides a series termination impedance for an output driver as well as shunt termination impedances for a receive circuit. These impedances are dynamically adjusted to match a ratio of an external precision resistor. Multiple coarse and fine-grain adjustments are automatically performed by the hardware. Adjustment may occur at power up or at programmable periodic intervals, and one or both of the impedances may be updated each time an interface begins to transmit or receive data. A specific embodiment utilizes a reference resistance that is made up of a parallel combination of resistors connected through MOS transistors. This resistance is adjusted by connecting or disconnecting the parallel resistors until it matches a ratio of an external resistor. The switch settings that provide a match are then used to adjust the termination impedances at the input and output pads.