摘要:
A circuit for a DRAM is described which, when in test mode, notifies a tester when the self-refresh operation of a dynamic random access memory (DRAM) reaches various stages of completion. By signaling the tester when, i.e., ⅛, ¼, ½, etc. of the self-refresh cycle is reached, the amount of time needed for verification of the self-refresh oscillator frequency is reduced correspondingly by a factor of 8, 4, 2 etc. The signaling of a partial test time is achieved by adding self-refresh status logic circuits which decode the high order most significant bits of the refresh address counter. The activation of the third most significant bit signals completion of ⅛th of the self-refresh cycle, the activation of the second most significant bit signals completion of ¼th of the self-refresh cycle, the activation of the most significant bit signals completion of ½ of the self-refresh cycle, and deactivation of the most significant bit signals completion of the self-refresh cycle.
摘要:
A timing scheme for multiple data clock activation with programmable delay for use in accessing a multiple CAS latency memory device. A multi-stage data propagation path is used to propagate a bit being accessed from a memory array of the device to an output line. Timing signals are generated so that in a CAS latency three mode, the timing signal that activates the next to last stage of the propagation path is triggered by an output clock signal that activates the last stage of the propagation path so that pulse from the output clock signal does not overlap with pulses of the timing signal that activates the previous stage. This timing scheme ensures the data lines feeding the last stage are not being restored while the last stage is sensing these data lines. A programmable delay circuit is used to adjust the timing of the output clock signal.
摘要:
A charge pump limits the voltages at nodes internal to the charge pump to reduce the risk of junction breakdown in the charge pump. The charge pump includes a first pump circuit, a second pump circuit, a first clamp and a second clamp. The first clamp limits the voltage level of a well by providing a current path from the well to the output lead when the voltage level of the well reaches a first predetermined limit. The voltage level at a node from which charge is redistributed to the well is limited by the second clamp, which is configured to provide a conductive path from the node to the output lead when the voltage level of the node reaches a second predetermined limit. The pump circuits can each include a logic circuit that is configured, depending on the level of an external supply voltage, to reduce the rate at which the capacitor node is boosted when the external supply voltage is relatively high. The logic circuit can also vary the voltage difference between the capacitor node and the external supply voltage to decrease the relative voltage level at the capacitor node relative to the level of the external supply voltage. These features also help reduce the risk of junction breakdown in the charge pump.
摘要:
The present invention provides a method and apparatus that accomplishes a high performance, random read/write SDRAM design by synchronizing the read and write operations at the data line sense amplifier. This enables the design to perform random read and write operations without varying cycle time issues or unbalanced margin issues. The data lines are used as bi-directional lines to accomplish high performance reads and writes with minimal additional wiring overhead required. During a read operation, read data is transferred from the memory cells of the device across a series of consecutive pairs of data lines to an input/output port of the memory device. The first pair of data lines is coupled to a data line sense amplifier. The additional pairs of data lines are coupled to additional amplifiers. During a read operation, data is transferred across the consecutive pairs of data lines according to the timing cycles of the respective amplifiers. In order to quickly drive the data signals during a write operation up the series of consecutive pairs of data lines, the timing signals for each of the pairs of data lines except the first pair of data lines are disabled so that the data lines are allowed to float, and then the data lines are overdriven with the write data so that the write data quickly transitions up the series of data lines to the selected data line sense amplifier, where it arrives at approximately the same time that read data normally arrives during the timing cycle for the data line sense amplifier.
摘要:
A semiconductor memory device with a pair of data lines for reading and writing data signals to and from a matrix of memory cells and an accelerator circuit for accelerating the generation of a data signal on at least one of the data lines is disclosed. Slow signal generation on the data lines is due to the characteristics of NFET pass gates passing high signals, or PFET pass gates passing low signals. In an implementation using NFET pass gates, the accelerator circuit includes a pair of cross-coupled PFET transistors, one of which is activated by the low signal on the opposing data line. The drains of the cross-coupled PFET transistors are coupled to the data lines, such that when the low signal on the opposing data line activates one of the PFETs, it supplies additional current to the data line receiving the high signal, so as to accelerate the generation of the high signal on the data line. Faster signal generation allows for the data line latches of the circuit to be set earlier, thus allowing the read cycle of the memory device to be faster. An additional result of the increased signal generation on the data line that is receiving a high signal is that at the end of the cycle when the two data lines are coupled together, their average voltage due to charge sharing tends to be closer to a desired midlevel voltage such that less power is required to bring the two data lines to the desired mid-level voltage at the end of the signal cycle.
摘要:
A voltage regulation scheme for an on-chip voltage generator includes a voltage sensing circuit (VSC) and a configurable buffer circuit (CBC) to regulate the on-chip voltage generator. The CBC generates an output signal that is received by the on-chip voltage generator to activate and de-activate the voltage generator. The VSC generates a voltage level detection (VLD) signal having a voltage level that is a function of the level of the on-chip generated voltage. The CBC receives a control signal that is used to dynamically configure the chip into an operational mode, as well as the VLD signal. In response to the control signal, the switch threshold of the CBC is configured to a predetermined level corresponding to the selected operational mode. The predetermined trip point causes the CBC to appropriately activate and de-activate the on-chip voltage generator to regulate the on-chip generated voltage at the level required by the configured operational mode. One embodiment of the CBC uses a configurable pull-up circuit to alter its switch threshold or trip point. The configurable pull-up circuit is used to pull-up the voltage at an intermediate node that is buffered and propagated to the on-chip voltage generator to activate and de-activate the voltage generator. The configurable pull-up circuit more strongly pulls up this voltage in one operational mode compared to another operational mode to alter the switch threshold.
摘要:
A regulator system for an on-chip-generated supply voltage includes a voltage detection circuit, a power-up mode detection circuit, a normal mode detection path, and a power-up detection path. The voltage detection circuit monitors the on-chip-generated supply voltage and generates a signal that indicates the level of this supply voltage. The power-up mode detection circuit detects when the chip is in the power-up mode and generates a path select signal. The path select signal causes the regulator system to select the power-up detection path during the power-up mode and to select the normal detection path when not in the power-up mode. The power-up detection path includes voltage regulation circuitry that does not rely on a reference voltage. In one embodiment, the power-up detection path includes a logic gate coupled to receive the signal from the voltage detector. The logic gate is skewed to have a trip point that corresponds to voltage level slightly greater than that of the external supply voltage. The logic gate controls the on-chip voltage generator to maintain the on-chip-generated voltage level at a magnitude greater than that of the external supply voltage. During power-up, the power-up detection circuit selects the power-up detection path, thereby avoiding the need to disable the on-chip voltage generator as in conventional systems that depend on a reference voltage.
摘要:
A regulator system includes first and second voltage sensing circuits coupled to a voltage generator control circuit. The first and second voltage sensing circuits are configured to monitor the voltage generated by the on-chip voltage generator (i.e., the on-chip supply voltage) and detect when the on-chip supply voltage reaches thresholds that are predetermined to define a desired range of the on-chip supply voltage. The voltage generator control circuit receives voltage sense signals from the voltage sense circuits and, in response, asserts or de-asserts a control signal received by the on-chip voltage generator so as to activate or de-activate the on-chip voltage generator to maintain the on-chip supply voltage within the desired range. The voltage generator control circuit introduces hysteresis in the generation of the control signal provided to the on-chip voltage generator. As a result of this hysteresis, once the on-chip voltage generator is activated, the voltage generator control circuit only de-activates the on-chip voltage generator when the on-chip supply voltage reaches the higher threshold. Conversely, once the on-chip voltage generator is de-activated, the voltage generator control circuit only activates the on-chip voltage generator when the on-chip supply voltage reaches the lower threshold.
摘要:
An ABIST circuit for testing a memory array has a blanket write subcycle (WC), an RC3 subcycle, and an RC4 subcycle. The ABIST circuit includes a programmable pattern generator that provides eight programmable data bits, eight programmable read/write bits, and two programmable address frequency bits to determine the specific test patterns applied to the memory array. The address frequency bits determine how many memory cycles will be performed on each cell of the memory array. In X1 mode, only one memory cycle is performed on each cell during any given subcycle. In X2 mode, two memory cycles are performed on each cell, allowing a cell to be written, then subsequently read in the same subcycle. In X4 mode, four memory cycles are performed on each cell, and in X8 mode, all eight bits of read/write and data are used on each cell, resulting in eight memory cycles for each cell within the memory array.
摘要:
A test method and structure is provided to determine the end count of a predetermined succession or series of binary numbers wherein one number and its relation in the succession to the end count number is known. The structure includes a circuit for generating a binary digit output and a device for storing at least a portion of the said one number which preferably is the penultimate number in a sequential series. A succession of binary numbers is generated as output of the circuit. the outputted numbers are compared to the portion of the stored number. A READY signal is outputted when the stored number compares with the outputted number. On a subsequent cycle, a control signal is generated when the generated number following the READY signal corresponds to the end count number. The inventor also contemplates programmable end count numbers.