摘要:
An active termination resistor is provided within a feedback loop circuit thus advantageously increasing the stability of the feedback loop circuit. In particular, the active termination resistor traces the impedance of the feedback loop such that R(f) = 1/GM3(f). The active resistor may also be configured to track the value of the resistor to set the feedback transconductance over process and temperature variations to ensure stability of the feedback loop over these variations.
摘要:
An embodiment of a pumped substrate system includes an oscillator, capacitive pump, comparing circuit, and a level shifter. The level shifter is coupled between the substrate and the positive input lead of the comparator and shifts the voltage level present on the substrate by a voltage Vbg. The comparator compares ground potential to the shifted substrate voltage. The oscillator, capacitive pump and comparing circuit form a negative feedback loop which operates to maintain the substrate voltage substantially equal to -Vbg. In one embodiment, the level shifter includes a band gap reference.
摘要:
A data security fuse system (35) for allowing one-time programmability of protected data cells in a reprogrammable logic device (10), which may determine, for example, the logic architecture of the device. The system includes a fuse enable circuit (100) which may be erased to the disabled state only prior to packaging of the device during manufacture. The protected data cells may be selected for programming by a decoder (30) which decodes cell selection signals. A security fuse circuit (300) is enabled by a fuse enable signal (SFE) from the activated fuse enable circuit. The security fuse circuit (300) allows the protected cells to be selected once for programming after the system has been activated, and thereafter defeats any attempts to access the protected data cells.
摘要:
Dispositif logique programmable après installation pouvant être configuré ou reconfiguré après son installation dans le système d'un utilisateur. Le dispositif décrit utilise des cellules de mémoire rémanente (455) telles que des transistors à porte flottante en tant qu'éléments programmables, et est donc à même de sauvegarder de manière virtuellement illimitée une configuration logique programmée particulière pendant l'état hors-tension. Le dispositif peut être utilisé dans un état normal et dans plusieurs états utilitaires permettant de reconfigurer le dispositif. L'état du dispositif est commandé par un automate fini interne (520) qui exécute plusieurs équations d'état dont les variables sont les niveaux logiques de commande de deux broches spécialisées et l'état actuel du dispositif. Une broche (470) du dispositif reçoit en série des données d'entrée qui chargent la bascule électronique (505) d'un registre à décalage. Le contenu de la bascule (505) est utilisé pour sélectionner une rangée particulière de cellules à programmer, de même que le niveau logique auquel les cellules sélectionnées doivent être programmées. Les entrées et les sorties normales du dispositif sont isolées de ce dernier pendant les états utilitaires, de sorte que le système de l'utilisateur n'interfère pas avec le fonctionnement du dispositif pendant les états utilitaires. Un circuit survolteur (530) produit le niveau de haute tension nécessaire pour programmer les transistors à porte flottante utilisés en tant que cellules de mémoire du dispositif, et est alimenté par la tension d'alimentation du dispositif, ce qui permet de réduire le nombre nécessaire de broches du dispositif. En programmant une cellule de mémoire particulière, l'utilisateur peut sélectionner l'état des sorties du dispositif pendant les états utilitaires et ceci soit sous la forme d'une condition de verrouillage de données actuelles, soit dans une condition à trois états.
摘要:
A programmable logic device is disclosed which is adapted to isolate the Miller capacitances of erased memory cells from the product terms and to limit the cell current drawn through the product term sense amplifiers. The invention substantially reduces the row switching noise coupled onto the product terms, allows high speed sense amplifier operation, and significantly reduces the power dissipated by the device. In accordance with the invention, the electrically erasable sense transistor M2 for each memory cell is disposed between the cell select transistor M1 and the product term sense amplifier, thereby isolating the Miller. capacitance associated with the select transistor from the sense amplifier when the cell is in the erased (nonconductive) state. Separate product term ground lines 35 are provided for each product term 30. A current limiter connects each product term ground line to ground, and is adapted to limit the current flow through each product term to a predetermined maximum level, typically about the maximum current level which may be passed through one conductive memory cell.
摘要:
An improved programmable logic device (PLD) is disclosed which employs electrically erasable memory cells which can be programmed and erased at high speed. The PLD memory cells comprise floating gate transistors as the storage elements, which are programmed and erased by Fowler-Nordheim tunneling. The PLD includes a serial register latch (SRL) 30 which is coupled to the product terms of the PLD array 10. Input programming data for a selected row of the array is serially entered into the SRL 1 0, and during a programming cycle the SRL data is employed to simultaneously program the storage elements of the selected row to either the enhancement mode or the depletion mode. The data programmed into the array 10 may be verified at high speed. The status of each of the cells in the selected row can be sensed using the normal sense amplifiers and loaded into the SRL 30 in parallel, and thereafter serially shifted out of the PLD for external verification. The PLD output logic and sense amplifiers can be functionally validated independent of the data in the array. Test data such as apparent array patterns are serially loaded into the SRL, and thereafter forced onto the normal sense amplifier inputs, propagated through the output logic and read out of the device output pin.