Abstract: An integrated circuit memory cell and voltage ladder design that adapts techniques typically applied to Static Random Access Memory (SRAM) circuits to implement a compact array of analog Voltage Random Access Memory (VRAM) locations. The memory cells in the VRAM each store a digital value that controls a corresponding switch. The switch couple a particular voltage from a set of voltages generated by the ladder, to be output when that location is enabled. Multiple analog output voltages are provided by simply providing additional rows of cells.

Abstract: A compact, differential clock input buffer that converts single-end or differential sine wave or square wave inputs into complementary squarewave digital outputs, with low-jitter, and 50% duty cycle outputs. Low-noise oscillator design concepts are applied to provide at least two stages of regeneration. This minimizes the time the clock buffer spends in the noise-susceptible linear region. A first stage latching circuit consists of a pair of cross coupled transistors (i.e., a differential transistor pair) with resistive loads to provide gain, limiting, hysteresis, and latching functions. These transistors operate in a linear region for only a very small range of input voltage. A second stage latching circuit, which can use a current mirror, is also provided as a pair of cross coupled transistors with resistive loads. The second stage latch provides positive feedback to further limit the linear operating range.

Abstract: A technique for dynamically calibrating a successive approximation charge to digital converter by toggling at least some portion of the converter between two predetermined states, with the design goal of balancing the voltage and/or charge that is output in the two states. The two states are chosen such that they are expected to generate the same output voltage when the converter is in normal operation mode. If there is an imbalance, switching between the two calibration states invariably generates a square wave signal that toggles between two distinct values. A synchronous demodulator having a bandwidth centered at the toggle frequency can then be used to accurately detect an amount of error, which is then feedback to generate correction signals. The detected value of the error signal can in turn can be further integrated over time, to provide a correction value.

Abstract: A circuit for adding or subtracting an amount of charge from a charge sample, such as in a Charge Coupled Device (CCD), by portioning and pipelining the processing stages, to avoid introducing a memory effect. The operation, such as subtraction, is split into multiple stages, with each stage responsible for removing only a portion of the total amount of charge that is desired to be removed. The subtraction pipeline stages operate together to remove the total desired charge amount. In one embodiment each successive subtraction stage removes a corresponding lesser amount of charge. As a result, greater accuracy in the amount of charge removed is achieved as well operation at higher frequencies than previous charge subtraction approaches.

Abstract: A biasing circuit for use with a Charged Coupled Device (CCD) that creates a gate bias voltage by maintaining a model or surrogate representation of the surface potentials within the CCD storage and barrier regions. In one embodiment the invention is a bias circuit that includes at least a first and second model transistor for modeling the two regions. The first model transistor is connected to a supply voltage to provide a first reference voltage at a first node, and models the first charge storage region. A resistive circuit element is coupled between the first node N1 and a second node N2 in order to allow a step voltage to be developed. The second model transistor is in turn connected to the second node N2 and provides the bias voltage at an output portion that can be used to control the gate of the barrier region. The model circuit therefore allows a proper bias voltage to be maintained through process and operating condition variations.