Method and circuit for reducing DRAM refresh power by reducing access transistor sub threshold leakage
First Claim
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1. A memory array, comprising:
- a plurality of memory cells arranged in rows and columns, each of the memory cells including a memory cell capacitor and an access transistor coupled to the memory cell capacitor;
a digit line for each column of memory cells in the memory array, each digit line being coupled to a plurality of access transistors in a respective column of memory cells;
a word line for each row of memory cells in the memory array, each word line being coupled to the gates of a plurality of access transistors in a respective row of memory cells;
a sense amplifier for each column of memory cells, each sense amplifier being coupled to the digit line for a respective column of memory cells, each sense amplifier having a power input and being operable to couple a supply voltage applied to the power input to the digit line to which it is coupled responsive to sensing a predetermined voltage level on the digit line; and
a voltage regulator coupled to the power input of the sense amplifiers for a plurality of columns of memory cells, the voltage regulator having at least one bipolar transistor coupled to the power inputs of the sense amplifiers, the voltage regulator being operable to generate the supply voltage and to regulate the magnitude of the supply voltage responsive to variations in current coupled from the voltage regulator to the sense amplifiers.
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Abstract
The required refresh rate of a DRAM is reduced by biasing active digit lines to a slight positive voltage to reduce the sub threshold current leakage of access transistors in memory cells that are not being accessed. The slight positive voltage is provided by a voltage regulator circuit using one or more bipolar transistors fabricated in a well that electrically isolates the bipolar transistors from the remainder of the substrate. The voltage provided by the voltage regulator is preferably coupled to the access transistors by powering each of the n-sense amplifiers in the DRAM with the voltage from the voltage regulator.
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2 Claims
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1. A memory array, comprising:
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a plurality of memory cells arranged in rows and columns, each of the memory cells including a memory cell capacitor and an access transistor coupled to the memory cell capacitor;
a digit line for each column of memory cells in the memory array, each digit line being coupled to a plurality of access transistors in a respective column of memory cells;
a word line for each row of memory cells in the memory array, each word line being coupled to the gates of a plurality of access transistors in a respective row of memory cells;
a sense amplifier for each column of memory cells, each sense amplifier being coupled to the digit line for a respective column of memory cells, each sense amplifier having a power input and being operable to couple a supply voltage applied to the power input to the digit line to which it is coupled responsive to sensing a predetermined voltage level on the digit line; and
a voltage regulator coupled to the power input of the sense amplifiers for a plurality of columns of memory cells, the voltage regulator having at least one bipolar transistor coupled to the power inputs of the sense amplifiers, the voltage regulator being operable to generate the supply voltage and to regulate the magnitude of the supply voltage responsive to variations in current coupled from the voltage regulator to the sense amplifiers.
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2-93. -93. (canceled)
Specification