Lattice Semiconductor Corporation

Microchip Technology Inc.

John Schadt

William B Andrews

Mou C Lin

Fulong Zhang

Larry Fenstermaker

Anthony K Myers

Brian W Yeager

Zheng Chen

Christopher D Gorsuch

Oscar G Mercado

Phillip Johnson

Barry Britton

Harold Scholz

David A Rhein

Warren L Ziegenfus

Ling Wang

Ming Hui Ding

Zheng (Jeff) Chen

Chien Kuang Chen

Jay H Angle

Craig Bingert

Hemanshu T Vernenker

Xiaojie He

Allen White

Steven J Fong

Sajitha Wijesuriya

Margaret Tait

Christopher Hume

Claudia A Stanley

Keith Truong

Nhon Nguyen

Ravi Lall

David Onimus

Stephen R Cebenko

Shawn Murray

Luan Phoc Chau

Thomas R Gustafson

Hal Scholz

An SEU immune flip-flop includes a master stage data latch having an input, an output, a clock input, being transparent in response to a clock signal first state and being latched in response to a clock signal second state, a slave stage data latch having an input coupled to the master stage data latch output, an output, a scan output, a slave latch clock input, a scan slave latch having an input coupled to the slave stage data latch scan output, an output, and a clock input, being transparent in response to the clock signal second state and being latched in response to the clock signal first state. The slave stage data latch includes a switched inverter disabled when the slave latch is in a transparent state and enabled when the slave latch is in a latched state having a time delay longer than an SEU time period.

Single event upset immune flip-flop utilizing a small-area highly resistive element

In certain embodiments of the invention, a serializer has a transfer stage that transfers N-bit parallel data from a relatively slow timing domain to a relatively fast timing domain and a serializing stage that converts the parallel data into serialized data. Between the transfer stage and the serializing stage is an update stage that buffers the data and can be used to toggle the serializer between an N&#x2212;1 operating mode and an N+1 operating mode.

Serializer with multiple stages

Two (or more) different, but complementary, families of integrated circuits having the same layout are developed simultaneously where the different families are achieved by changing one or more design parameters of transistors used to implement the integrated circuits. For example, a low-power (but low-speed) family of one or more ICs (e.g., for handheld applications) can be achieved by designing at least some transistors with relatively high threshold-voltage (Vt) levels, while a different, but complementary, high-speed (but high-power) family of one or more ICs (e.g., for server applications) can be achieved by designing corresponding transistors with relatively low Vt levels. In this way, the two families can share in common all but a very few masks used to fabricate the ICs of the different families.

Simultaneous development of complementary IC families

In one embodiment, a configurable delay element has three stages. The first stage has an 8-buffer first delay chain and an (8&#xd7;1) first mux that selects one of the eight first-delay-chain outputs. The second stage has a 24-buffer second delay chain connected to receive the first-mux output and organized into three 8-buffer sub-chains and a (4&#xd7;1) second mux that selects one of the four second-delay-chain outputs. The third stage has a 96-buffer third delay chain connected to receive the second-mux output and organized into three 32-buffer sub-chains and a (4&#xd7;1) third mux that selects one of the four third-delay-chain outputs as the delay-element output signal. A delay-element controller provides glitch-less updates to the signal used to control the delay-element muxes by timing those updates to occur when all delay-element buffers have the same state. The controller bases the update timing on the delay-element output signal.

Low-power configurable delay element

In one embodiment of the invention, a programmable device, such as an FPGA, has a programmable input buffer with a VCCIO-powered buffer stage for high-voltage signaling and a VCC-powered buffer stage for low-voltage signaling. In addition to a main driver section, the VCCIO-powered buffer stage has a mixed-mode section for handling multiple different over-drive and multiple different under-drive conditions, a hysteresis section for providing multiple different trip-point hysteresis modes of operation, and a level-shifting section with look-ahead circuitry that enables the main driver section to be implemented with low-power, high-threshold devices, while still enabling the VCCIO-powered buffer stage to operate with low skew and high speed.

Programmable buffer

In certain embodiments of the invention, a serializer has (a) an initial, transfer stage that transfers incoming parallel data from a relatively slow timing domain to a relatively fast timing domain and (b) a final, serializing stage that converts the parallel data into serialized data. Between the transfer stage and the serializing stage is an update stage that (i) buffers data between the initial and final stages and (ii) can be used to toggle the serializer between an N&#x2212;1 operating mode (that serializes (N&#x2212;1) bits of parallel data) and an N+1 operating mode (that serializes (N+1) bits of parallel data) to achieve a net N:1 gearing ratio where N is an odd integer. The serializer can be configurable to support other gearing ratios as well.

Serializer with odd gearing ratio

Low-power, glitch-less, configurable delay element

In one embodiment of the invention, a receiver has two mux circuits, two receiver circuits, and a mixer. The muxes select first and second input signals for the receiver circuits. A p-type transistor in a transmission gate in each mux is connected (i) at its channel nodes between a pad and the mux output and (ii) to receive a control signal at its gate node. Control circuitry for the p-type transistor implements a threshold reduction filter that ensures that a maximum voltage level at the mux output is at least a threshold below the mux's power supply voltage. Based on first and second input signals, the first receiver circuit generates first and second intermediate signals, and the second receiver circuit generates third and fourth intermediate signals. The mixer circuit combines the intermediate signals to generate first and second output signals, wherein the first and second receiver circuits effectively operate over different ranges of common-mode voltages.

Receiver for differential and reference voltage signaling with programmable common mode

In one embodiment, an integrated circuit such as an FPGA includes one or more data I/O blocks, one or more FIFOs, and a FIFO controller. At least one data I/O block receives an incoming bit stream from an external device. At least one FIFO is connected to receive a corresponding incoming bit stream from a corresponding data I/O block. The FIFO controller controls operations of the one or more FIFOs, such that (i) bits from the corresponding data I/O block are written into the at least one FIFO using a FIFO write clock that is based on an incoming clock signal and (ii) bits are read out from the at least one FIFO using a FIFO read clock that is based on a local reference clock signal.

Distributed front-end FIFO for source-synchronous interfaces with non-continuous clocks

In one embodiment, an integrated circuit, such as an FPGA, has one or more programmable termination schemes, each having a plurality of resistive termination legs connected in parallel, and a calibration circuit designed to control each termination scheme for process, voltage, and temperature (PVT) variations. A sense element in the calibration circuit and each resistive leg in each termination scheme has a transistor-based transmission gate connected in series with a non-silicided poly (NSP) resistor. The negative temperature coefficient of resistivity of each NSP resistor offsets the positive temperature coefficient of resistivity of the corresponding transmission gate to provide a temperature-independent sense element and temperature-independent termination legs. The temperature-independence and constant IV characteristic of the sense element and termination legs enable a single calibration circuit to simultaneously control multiple termination schemes operating at different termination voltage levels.

Temperature-independent, linear on-chip termination resistance

In one embodiment of the invention, a bias signal monitor has two signal comparators that compare two (power supply) voltages at two different bias points and a logic circuit that processes the outputs from the two signal monitors to generate a bias signal monitor output signal. The logic circuit implements hysteresis-based processing such that (1) if both signal comparators are active (indicating that a first voltage is greater than the second voltage relative to both bias points), then the monitor output is active, (2) if both signal comparators are inactive (indicating that the first voltage is not greater than the second voltage relative to either bias point), then the monitor output is inactive, and (3) if one signal comparator is active and the other is inactive, then the monitor output keeps its previous value. This hysteresis characteristic prevents relatively small oscillations between the voltages from changing the monitor output.

Hysteresis-based processing for applications such as signal bias monitors

In one embodiment of the invention, a programmable level shifter can be selectively configured to operate in either a high-speed mode or a low-power mode. In both modes, the level shifter converts an input signal in one power supply domain into an output signal in another power supply domain. In the high-speed mode, p-type devices are configured as a current-mirror amplifier that provides the level shifter with relatively fast switching speed. In the low-power mode, the same p-type devices are configured as a cross-coupled latch that provides the level shifter with relatively low power consumption. Selectively enabled n-type devices provide the low-power mode with larger effective n-type devices to flip the cross-coupled latch formed by the p-type devices in the low-power mode.

Programmable level shifter

In one embodiment, an integrated circuit has configurable application circuitry that operates at any one of multiple available power supply voltages. PT-control circuitry, operating at a PT reference voltage, generates a PT-control signal indicative of variations in process and temperature. Application-control circuitry controls the configuration of the application circuitry based on the selected power supply voltage for the application circuitry and the PT-control signal, where the selected power supply voltage is independent of the PT reference voltage. In one implementation, the application circuitry is an output driver having source and sink driver blocks, where driver-control circuitry controls the configuration of the source driver block based on the selected output-driver power supply voltage, a source PT-control signal, and a selected drive strength, while controlling the configuration of the sink driver block based on the selected output-driver power supply voltage, a sink PT-control signal, and a selected drive strength.

Integrated circuit having independent voltage and process/temperature control

In one embodiment of the invention, an integrated circuit, such as an FPGA, comprises a distributed FIFO architecture that supports data transfer from an external device, such as an SDRAM, via an interface that receives a non-continuous, asynchronous strobe clock and a data lane having a plurality of bit lines from the external device. The distributed FIFO architecture comprise a FIFO for each bit line and a FIFO controller. Under control of the FIFO controller, data is written into each FIFO using a FIFO write clock based on the strobe clock, while data is read out from each FIFO using a FIFO read clock based on a local reference clock of the integrated circuit. The distributed FIFO architecture is designed to handle a range of possible phase differences between the FIFO write and read clocks to safely convert from the asynchronous, non-continuous strobe domain to a local continuous clock domain.

Distributed front-end FIFO for source-synchronized interfaces with non-continuous clocks

In one embodiment of the invention, an integrated device has interface circuitry that includes a dynamic monitor that monitors the relative potential between (at least) two different power supplies to enable the device to react to over-voltage conditions such that appropriate selections can be made for which power supplies are selected for different components in the interface circuitry, such as output drivers and input receivers. The dynamic monitor enables over-voltage protection to be automatically implemented before the device has been configured, such as during the device's power-on state.

Growing community of inventors

Bethlehem, PA, United States of America

John Schadt