Altera Corporation

John C Costello

Myron Wai Wong

Raminda U Madurawe

James D Sansbury

Bruce B Pedersen

Peter John McElheny

William Bradley Vest

Dirk Alan Reese

Rakesh H Patel

Irfan Rahim

John E Turner

Richard G Smolen

Stephanie T Tran

Janusz K Balicki

Mark W Fiester

Nghia Tran

Ying Xuan Li

Chiakang Sung

Krishna Rangasayee

Rafael Czernek Camarota

John Henry Bui

Minchang Liang

Cheng H Huang

Guu Lin

Behzad Nouban

Robert R N Bielby

Bruce F Mielke

Chuan-Yung Hung

Michael Hsiao-Ming Chu

W Bradley Vest

Gwen G Liang

Bruce E Mielk

Bruce E Mielke

Peter J Mcelheny

A memory circuit including a voltage divider with a first phase change memory (PCM) device and a second PCM device coupled to the first PCM device is described. In one embodiment, the first PCM device is in a set resistance state and the second PCM device is in a reset resistance state. Also, in one embodiment, the voltage divider further includes a first switch coupled to the first PCM device and a second switch coupled to the first switch and the second PCM device. In one embodiment, the memory circuit further includes a half latch coupled to the voltage divider and a cascade transistor coupled to the half latch and the voltage divider.

Non-volatile memory circuit including voltage divider with phase change memory devices

Circuits, methods, and apparatus for limiting voltages received by devices in input/output cells to less than the device's breakdown voltage. An exemplary embodiment of the present invention provides an input/output cell having one or more clamp diodes and resistors configured to limit voltages seen by the gates of the devices in the input/output cell. In one embodiment, the clamp diodes are on-chip, while the resistors are off-chip. In a specific embodiment, the clamp diode is connected between an input pad for the input output cell and a supply voltage VCC, while a resistor is off-chip and in series with the input pad. In another specific embodiment, a series of clamp diodes are coupled between ground and an input pad, while a resistor is off-chip and in series with the input pad. In another embodiment, the clamp diode or diodes may be programmably or selectively disconnected. These clamp diodes may be disabled to protect against latch-up. Integrated circuits that are consistent with the present invention may include one or more of these and the other features described.

High voltage tolerance emulation using voltage clamp for oxide stress protection

The present invention optimizes the performance of integrated circuits by adjusting the circuit operating voltage using feedback on process/product parameters. To determine a desired value for the operating voltage of an integrated circuit, a preferred embodiment provides for on-wafer probing of one or more reference circuit structures to measure at least one electrical or operational parameter of the one or more reference circuit structures; determining an adjusted value for the operating voltage based on the measured parameter; and establishing the adjusted value as the desired value for the operating voltage. The reference circuit structures may comprise process control monitor structures or structures in other integrated circuits fabricated in the same production run. In an alternative embodiment, the one or more parameters are directly measured from the integrated circuit whose operating voltage is being adjusted.

On-chip voltage regulator using feedback on process/product parameters

A programmable input/output device for use with a programmable logic device (PLD) is presented comprising an input buffer, an output buffer and programmable elements. The programmable elements may be programmed to select a logic standard for the input/output device to operate at. For instance, a given set of Select Bits applied to the programmable elements may select TTL logic, in which case the input and output buffers would operate according to the voltage levels appropriate for TTL logic (e.g., 0.4 volts to 2.4 volts). For a different set of Select Bits, the GTL logic standard would be applied (e.g., 0.8 volts to 1.2 volts). The invention enables a single PLD to be used in conjunction with various types of external circuitry.

System for coupling programmable logic device to external circuitry which selects a logic standard and uses buffers to modify output and input signals accordingly

Circuits may provide series on-chip termination impedance to one or more input/output pins. In one embodiment, two off-chip reference resistors in combination with internal calibration circuitry are used to control termination transistors coupled to several input/output (I/O) pins. The termination transistors behave as programmably adjustable termination resistors that match the impedance of external resistors. By using only a small number of reference resistors (e.g., 2 resistors) for a large number of I/O pins, the present invention eliminates the external components that would otherwise be needed to provide resistance termination. The effective series termination resistance may be programmed, enabling the termination resistance to meet different I/O standards. Further, the resistance termination techniques of the present invention are not sensitive to process, voltage supply, and temperature (PVT) variations.

Programmable series on-chip termination impedance and impedance matching

A technique for providing ESD protection for integrated circuit devices with multiple power and/or ground buses is provided. The technique involves using a clamping device that is capable of handling both positive and negative ESD pulses to clamp each power bus, ground bus, and I/O pad within a device to a respective one of the ground buses. Without resorting to exhaustive cross-clamping, this arrangement provides a discharge path for an ESD pulse applied across any combination of power buses, ground buses, and I/O pads during an ESD event.

Technique for protecting integrated circuit devices against electrostatic discharge damage

Disclosed is a method and apparatus for evaluating margin voltages in single poly EEPROM cells. Briefly, the invention involves shifting the cell's threshold voltage higher, resulting in a corresponding rise in the margin voltage, so that testing for the erase margin may be conducted in the positive voltage range. The present invention implements a variety of solutions to the problem, including both innovations in cell processing and circuitry. In one embodiment, the process steps employed to create the floating gate transistor are changed in order to increase its threshold voltage. Alternatively, or in combination with these general process changes, the width of the floating gate transistor may be reduced, resulting in a corresponding increase in the margin voltage. Circuit modifications include providing a separate test mode condition where the sense amp trip current is higher than under normal operation, and raising the source line's voltage level with a new sense amp optimization, or only during the margin testing mode, both of which shift the erase margin voltages for the cell into the testable range.

Apparatus and method for margin testing single polysilicon EEPROM cells

A technique is provided for improving the output drive capacity of output drivers on an integrated circuit that is configured to support I/O standards having operating voltages greater than the intrinsic core supply voltage. When MOS field-effect transistors are used in the I/O circuitry of such integrated circuits, the gate oxide layers of the transistors in the interface circuitry may need to be thicker than those comprising the core circuitry in order to tolerate I/O voltages that exceed the core supply voltage. In counteracting the degradation in output drive that may result from thickening the gate oxide layer, the pull-down signal applied to the gate of the pull-down transistor is preferably level-shifted from the core supply voltage to the higher external operating voltage associated with the I/O standard being supported. This external voltage is made available to the level-shifting circuit preferably through a spare pin or a gated I/O pin.

Input/output drivers

A macrocell for a programmable logic device includes circuitry for allowing a neighboring macrocell to borrow various numbers of the product terms of the macrocell. The macrocell can continue to make full use of its product terms that are not thus borrowed. This includes logically combining and registering the unborrowed product terms. The macrocell may include circuitry for feeding back to the AND array of the programmable logic device a combinatorial or registered signal of the macrocell, and also outputting such a combinatorial or registered signal from the macrocell. When a combinatorial signal is fed back, the register of the macrocell can be used for another signal of the macrocell.

Programmable logic device macrocell with improved logic capability

An integrated circuit contains circuitry to operate in such a fashion to reduce output noise when switching output circuits from a programming mode to a user mode. In an implementation, the integrated circuit (,) is configurable in the programming mode with user configuration data. In the user mode, the integrated circuit will operate with the functionality as defined by the user during the programming mode. When switching from the programming mode to the user mode, each output (,) of the integrated circuit will switch to its user mode value. In order to minimize switching noise, the outputs are released to their user mode values not all at the same time.

Reducing I/O noise when leaving programming mode

A system for generating voltages on an integrated circuit utilizes an overlapping clocking scheme. An oscillator generates the overlapping clock signals, which are coupled through oscillator buffers, to row pumps. In response to the overlapping clock signals, row pumps generate high voltages, typically higher than the VDD voltage of the integrated circuit. These high voltages may be used to program programmable memory cells or interface to logic components of the integrated circuit.

High voltage pump scheme incorporating an overlapping clock

An output buffer comprising control circuit for reducing the amount of ground and/or power bounce noise. The output buffer further includes one or more driver devices. The output current of the driver device(s) is limited by providing an intermediate drive voltage to the control electrode of the driver device. A pass device (or a transmission gate) provides the intermediate drive voltage and also operates as a variable resistive device that limits the slew rate of the drive voltage. The operation of the pass device can be dependent on a signal level at the output of the output buffer. When the output has transitioned to a new logic state, the new logic level is fed back to change the operating state of the pass device, thus ensuring that the output voltage meets the output VOL and VOH specifications.

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Los Altos, CA, United States of America

John C Costello