Abstract:
A dual phase synchronous race delay clock circuit that will create an internal clock signal in an integrated circuit that is synchronized with and has minimum skew from an external system clock signal is disclosed. The synchronous race delay circuit has an input buffer circuit to receive, buffer, and amplify an external clock signal. The input buffer circuit has a delay time that is the first delay time. A fast pulse generator is connected to the input buffer circuit to create a fast pulse signal. The fast pulse generator is connected to a slow pulse generator to create a slow pulse signal. The fast pulse generator and the slow pulse generator is connected to a race delay measurement means to determine a measurement of a period of the external system clock by comparing a time difference between the slow pulse signal and a following fast pulse signal. A delay control means is connected to the race delay measurement means to receive the measurement of the period of the external system clock. The delay control means will create a first phase control pulse and a second phase control pulse. A duty cycle synchronizer means is connected to the delay control means to create the dual phases of the internal clock from the first phase control pulse and the second phase control pulse. An internal buffer will buffer and amplify the two phases of the internal clock signal that is aligned with the external clock signal to have minimum skew.
Abstract:
A high speed test circuit receives a tester clock from a tester and it conducts a test on a circuit under test. The high speed test circuit generates a high frequency clock according to the tester clock, so it is capable of operating in two frequencies. The high speed test circuit tests the circuit under test according to the high frequency clock, and it performs a low speed operation according to a low frequency clock, which is for example the tester clock.
Abstract:
A multiple phase latched type synchronized clock circuit that will create a multiple phases of an internal clock signal in an integrated circuit that is synchronized with an external system clock signal is disclosed. A latched type clock synchronizer circuit has an input buffer circuit to receive the external input clock to create a first timing clock. The input buffer is connected to a delay monitor circuit to delay the first timing clock by a first delay factor to create a second timing clock. A delay measurement latch array is connected to the input buffer circuit and the delay monitor circuit to create a latched measurement signal, which indicates a period of time between a second pulse of the first timing clock and a first pulse of the second timing clock. A multiple delay array is connected to the input buffer to receive the first timing clock and will create multiple pluralities of incrementally delayed timing clocks. The multiple pluralities of incrementally delay timing clocks and the latched measurement signal are the inputs to a plurality of phase generators that create a plurality of third timing clocks. Each of a plurality of internal buffers is connected to each of the phase generators to receive one of the third timing clocks. The third timing clock is shaped to create one of the multiple phases of the internal clocks which are then buffered, amplified and transmitted to the integrated circuit.
Abstract:
A high speed test circuit receives a tester clock from a tester and it conducts a test on a circuit under test. The high speed test circuit generates a high frequency clock according to the tester clock, so it is capable of operating in two frequencies. The high speed test circuit tests the circuit under test according to the high frequency clock, and it performs a low speed operation according to a low frequency clock, which is for example the tester clock.
Abstract:
An improved input buffer circuit of the type having a chain of FET inverter circuits has an FET connected in a feedback loop that functions like a Schmidt trigger and counteracts a hysteresis effect that causes variations in the delay of the inverter circuits and compensation for process variation. An FET is connected to conduct in its source-drain circuit between one of the power supply terminals and the interconnection node of two of the inverters in the chain. The gate of FET is connected to receive a signal from the output of one of the inverters. The hysteresis effect is characterized by different rising and falling paths at one knee of the transfer curve that describes the switching operation. The channel type of the FET and the polarity of the power supply terminal are selected to provide feedback during the transition where the knee occurs.
Abstract:
In this invention two compression circuits are combined to produce at a single output pass/fail condition for a plurality of memory addresses and a plurality of I/O. The output of an address compression circuit is connected to an I/O circuit. An I/O compression circuit is connected to several I/O circuits and the output of the I/O compression circuit controls a selected data output driver to provide a combined test result of the plurality of addresses and the plurality of I/O. The combination of the two compression circuits is made possible because the address data compression circuits and the I/O compression circuits use different truth tables.
Abstract:
A method and an apparatus are provided for image stabilization for the output of analog-to-digital converters (ADC) and for phase-locked loops (PLL). The digital coding at the output of ADCs and PLLs is filtered by this method and apparatus to eliminate the noise which has contaminated the coding. The noise sources are noise picked up by the cable, system board noise, ADC power and ground noise paths, and switching noise. The differences of energy level of sequential pixels in the ADC and PLL digital outputs used in image displays are used to decide if correction is required. The method of image noise filtering is compatible with programmable circuitry. This allows the method to be tuned for optimal image stabilization.
Abstract:
The invention discloses a new architecture of multiphase delay-locked loop (DLL) with innovative 3-edge phase detector (3-edge PD), which compares the VCDL's first delay interval and the last delay interval to send an Up pulse or a Dn pulse to adjust the interval among those delay clock phases. The DLL may achieve both wide-range operation and multiple clock phase generation, and is also immune to multi-selection problem.
Abstract:
This invention provides a method and apparatus for displaying an unscaled image frame on an LCD panel. The method and apparatus uses the same line buffers available to the digital signal processor DSP formerly used for scaling the displayed image up or down in size. No extra frame buffers are required by this invention since the frame rates of the source image and the LCD panel are the same. The image frame buffer is written to the LCD panel on every other panel vertical synchronization pulse. The vertical synchronization timing is shifted to the left or right in the time domain to center the image on the LCD panel.
Abstract:
A method to reduce clock noise in a multiple clock circuit is achieved. The method comprises, first, providing a periodic signal. Next, a first clock signal is provided having a frequency that is a constant multiple of the frequency of the periodic signal. Finally, a second clock signal is derived from the periodic signal. The second clock signal has a frequency that is a non-constant multiple of the periodic signal frequency. The non-constant multiple comprises the sum of a constant value plus a time-varying value. The spectral energy at the sum and difference frequencies of the first and second clock signals is reduced by frequency distribution spreading. A circuit is achieved comprising the above method.