The assignee for this patent, patent number 8618786, is
Reporters obtained the following quote from the background information supplied by the inventors: "This invention relates to voltage regulation circuitry, and more particularly, to voltage regulation circuitry that can provide an accurate regulated voltage without requiring external voltage reference sources.
"Transistors on digital integrated circuits may behave like electrical switches that turn on or off depending on the voltages that are applied at their terminals. Many integrated circuits are based on n-channel metal-oxide-semiconductor (NMOS) transistors and p-channel metal-oxide-semiconductor (PMOS) transistors. An NMOS transistor is a four terminal device having a gate terminal, a drain terminal, a source terminal, and a body terminal.
"The gate of an NMOS transistor can be driven to a logic high value (i.e., a positive power supply voltage) to turn the transistor on. When the transistor is on, current may flow from the drain to the source through the channel of the transistor. The channel of the NMOS transistor may be formed beneath the gate of the NMOS transistor. The gate of the NMOS transistor may be driven to ground (e.g., zero volts) to turn the device off. When the device is off, current may stop flowing. PMOS transistors may likewise be turned on and off by applying respective logic low and logic high values on their gates.
"As transistors are reduced in size and as supply voltages are decreased with improvements in process technology, it may become difficult to ensure that transistors are fully switched off. For example, even when the gate of an NMOS transistor is grounded, a leakage current may still flow between the drain and the source. Leakage currents can pose problems in modern integrated circuit designs. For example, leakage currents may result in excess power dissipation, undesired discharging of dynamic voltages, robustness issues, and overall performance degradation. Leakage current is typically small in comparison to the normal current of a device that is on.
"In certain integrated circuit applications, the presence of leakage may reduce manufacturing yield. In applications that require memory, for example, leakage effects may cause data to be read incorrectly from a memory array. For example, even if a memory cell within the memory array were storing a correct value (e.g., a logic value of '1'), an unsuccessful read operation would result in the reading out of an incorrect value (e.g., a logic value of '0'). The presence of unsuccessful reads from the memory array may render the die that the memory array is formed on defective, making it necessary to discard the die. It may be possible to reduce leakage by providing appropriate bias voltages to the transistors an integrated circuit. Care should be taken, however, to avoid undesirable cost and complexity in bias voltage sources on an integrated circuit. Care should also be taken to ensure that bias voltage sources perform satisfactorily despite changes in fabrication process conditions, operating voltage, and operating temperature (i.e., despite process-voltage-temperature or PVT variations).
"It would therefore be desirable to be able to provide improved voltage regulation circuitry such as voltage regulation circuitry for supplying voltages that reduce transistor leakage currents."
In addition to obtaining background information on this patent, VerticalNews editors also obtained the inventors' summary information for this patent: "Integrated circuits may be provided with voltage regulation circuitry. The voltage regulation circuitry may produce a negative voltage. The negative voltage may be used to reduce leakage or may be used in other circuit applications. A self-biasing arrangement may be used to ensure that the voltage regulation circuitry is not difficult or costly to manufacture while exhibiting good immunity to process-voltage-temperature variations.
"The voltage regulation circuitry may be used in any suitable integrated circuit. For example, the voltage regulation circuitry may be used in a programmable integrated circuit such as a programmable logic device integrated circuit. A programmable integrated circuit may have a configuration memory array that stores configuration data. Data may be stored in the configuration memory array to program and thereby customize programmable logic in the programmable integrated circuit. Data may be read from the memory array to confirm that the correct values have been written.
"Integrated circuits with the voltage regulation circuitry may supply a regulated output voltage. For example, the voltage regulation circuitry may produce an output voltage less than 0 volts. The voltage regulation circuitry may receive a positive power supply voltage from external supply pins or an on-chip source and may receive a negative supply voltage from an internal charge pump or from external source. Based on these power supply voltages (e.g., the positive power supply voltage and the negative supply voltage), the voltage regulation circuitry may provide an accurate regulated voltage that can be fed to the configuration memory array to help reduce leakage. In other integrated circuits, the regulated voltage can be used in other circuit applications.
"The voltage regulation circuitry need not include a bandgap reference circuit. Rather, the voltage regulation circuitry may be self-biased by forming a reference voltage source from the same power supply voltages that are used in producing the regulated output.
"The voltage regulation circuitry may be implemented using an error amplifier in a negative feedback configuration. The voltage regulation circuitry may have a first resistor string (chain) and a second resistor string (chain). The first and second resistor strings may have matched (e.g., identical) configurations and resistor values. The error amplifier may have a first (positive) input and a second (negative) input connected to the second resistor string and the first resistor string, respectively. The first and second resistor strings may be trimmable to adjust the regulated voltage. The first and second resistor strings may be trimmed in the same way by a common trimming control circuitry. With one suitable arrangement, trimming functions may be implemented using a resistor string with an adjustable tap point. The location of the tap point may be adjusted by selectively blowing fuses that control associated control transistors (as an example).
"The voltage regulation circuitry may exhibit inherent offset cancellation due to the matching of the first and second resistor strings. As a result, the regulated voltage may be stable over a relatively wide range of process, temperature, and voltage variations.
"The regulated voltage may be applied to the terminals of transistors on an integrated circuit to help reduce leakage currents. For example, the regulated voltage may be negative and may be applied to the gates of address (access) transistors within the memory array. Address transistors may have very thin gate oxides with relatively small breakdown voltages. When controlling these transistors, control voltage magnitudes may be restricted so as not to overstress the address transistors. In particular, gate-to-source voltages may be maintained below the gate breakdown voltage. An accurate well defined voltage is helpful in preventing the inadvertent overstressing of the transistors. Reducing the leakage of address transistors may be desirable for more robust read operations. More robust read operations can help confirm that correct data has been written and may help increase the yield of the integrated circuit.
"Further features of the voltage regulation circuitry, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description."
For more information, see this patent: Perisetty, Srinivas; Sherigar, Arvind. Self-Biased Voltage Regulation Circuitry for Memory. U.S. Patent Number 8618786, filed
Keywords for this news article include: Electronics, Semiconductor,
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