z-ram(zero capacitance ram)

Z-RAMZ-RAM

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RAMRAM

SRAM SRAM DRAM Z-RAM

SRAMSRAM Uses six transistorsUses six transistors It’s a slower memoryIt’s a slower memory It’s fabrication is difficultIt’s fabrication is difficult

DRAMDRAM

It uses a transistor and a capacitorIt uses a transistor and a capacitor It denser than SRAMIt denser than SRAM It fastest of the threeIt fastest of the three It’s fabrication is difficultIt’s fabrication is difficult

Z-RAMZ-RAM It’s Zero capacitance RAMIt’s Zero capacitance RAM It’s the cheapest RAMIt’s the cheapest RAM It’s built on SOI wafersIt’s built on SOI wafers SOI wafers contains a layer of silicon SOI wafers contains a layer of silicon

dioxide insulation buried below a dioxide insulation buried below a silicon surfacesilicon surface

It’s developed by Innovative Silicon It’s developed by Innovative Silicon Inc. Inc.

Z-RAMZ-RAM It’s fabrication is easierIt’s fabrication is easier It is denser It is denser A single cell consist of a single A single cell consist of a single

transistortransistor It’s quiet smallerIt’s quiet smaller It’s production cost is lowIt’s production cost is low It’s faster than SRAMIt’s faster than SRAM

Z-RAMZ-RAM

WRITING A ‘1’ TO Z-WRITING A ‘1’ TO Z-RAMRAM

Passing a current through the Passing a current through the channel builds up excess positive channel builds up excess positive charges in the transistor, which charges in the transistor, which decreases the threshold voltage and decreases the threshold voltage and the current flowing through the the current flowing through the channel. This action writes binary 1 channel. This action writes binary 1 to the bit-cell. to the bit-cell.

WRITING A ‘0’ TO Z-WRITING A ‘0’ TO Z-RAMRAM

Applying a bias to the transistor Applying a bias to the transistor channel removes the holes through channel removes the holes through the junction, writing binary 0. the junction, writing binary 0. Innovative Silicon refers to positive Innovative Silicon refers to positive charging as “impact ionization” and charging as “impact ionization” and to negative charging as” hole to negative charging as” hole removal.”removal.”

READING FROM A Z-READING FROM A Z-RAMRAM

Reading a Z-RAM bit-cell is similar to reading any DRAM cell. The chip applies a small pulse to the cell’s transistor and uses a sense amplifier to compare the resulting current flow with the current in a reference cell.

COMPARISONCOMPARISON

Z-RAMZ-RAM SRAMSRAM

Structure Structure 1 Transistor1 Transistor 6 Transistor6 Transistor

CapacityCapacity Highly denseHighly dense Less denserLess denser

PerformancePerformance High speed High speed SlowerSlower

FabricationFabrication Simple Simple Complicated Complicated

COMPARISONCOMPARISONZ-RAMZ-RAM DRAMDRAM

Structure Structure 1 Transistor1 Transistor 1 Transistor 1 Transistor ++1 Capacitor1 Capacitor

CapacityCapacity Highly denseHighly dense Less denserLess denser

PerformancePerformance ComparativelComparatively slowery slower

Faster Faster

FabricationFabrication Simple Simple Complicated Complicated

AdvantagesAdvantages Z-RAM read/write performance is Z-RAM read/write performance is

faster than conventional DRAM.faster than conventional DRAM. It’s the cheapest ram.It’s the cheapest ram. Z-RAM is twice as dense as Z-RAM is twice as dense as

conventional DRAM and about five conventional DRAM and about five times denser than SRAM.times denser than SRAM.

SOR is comparatively lower for Z-RAM.SOR is comparatively lower for Z-RAM. It’s fabrication is quiet simple.It’s fabrication is quiet simple. Low power consumption. Low power consumption.

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