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Day 26: November 10, 2010 Memory Periphery
ESE370: Circuit-Level Modeling, Design, and Optimization for Digital Systems Day 26: November 10, 2010 Memory Periphery Penn ESE370 Fall DeHon
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Today Decode Sensing Penn ESE370 Fall DeHon
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Memory Bank Penn ESE370 Fall DeHon
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Row Select Logically a big AND
May include an enable for timing in synchronous Penn ESE370 Fall DeHon
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Row Select How can we do better? Area Delay
Match to pitch of memory row Penn ESE370 Fall DeHon
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Row Select Compute inversions outside array
Just AND appropriate line (bit or /bit) Penn ESE370 Fall DeHon
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Row Select Share common terms Multi-level decode
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Row Select Same number of lines Half as many AND inputs
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Row Select: Precharge NAND
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Sensing Penn ESE370 Fall DeHon
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Differential Sense Amp
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Differential Sense Amp
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“Inverter” Penn ESE370 Fall DeHon
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“Inverter” Input high Input low Ratioed like grounded P
Pulls itself up Until Vdd-VTP Penn ESE370 Fall DeHon
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DC Transfer Function Penn ESE370 Fall DeHon
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Differential Sense Amp
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Differential Sense Amp
“Inverter” output controls PMOS for second inverter Sets PMOS operating point current Penn ESE370 Fall DeHon
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Differential Sense Amp
View: Current mirror Biases where inverter operating Penn ESE370 Fall DeHon
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Differential Sense Amp
View: adjusting the pullup load resistance Changing the trip point for “inverter” Penn ESE370 Fall DeHon
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DC Transfer /in with in=0.5V
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DC Transfer Various in Penn ESE370 Fall DeHon
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After Inverter Penn ESE370 Fall DeHon
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Connect to Column Equalize lines during precharge
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Singled-Ended Read Penn ESE370 Fall DeHon
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5T SRAM Penn ESE370 Fall DeHon
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Single Ended Need reference to compare against
Want to look just like bit line Equalize with bit line Penn ESE370 Fall DeHon
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Split Bit Line Split bit-line in half Precharge/equalize both
Word in only one half Only it switches Amplify difference Penn ESE370 Fall DeHon
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Open Bit Line Architecture
For 1T DRAM Add dummy cells Charge dummy cells to Vdd/2 “read” dummy in reference half Penn ESE370 Fall DeHon
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Memory Bank Penn ESE370 Fall DeHon
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Admin Have memory cell Andrew office hours Wednesday and Thursday
Add drivers and amps Andrew office hours Wednesday and Thursday Penn ESE370 Fall DeHon
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Idea Minimize area of repeated cell Compensate with periphery
Amplification (restoration) Match periphery pitch to cell row/column Decode Sensing Writer Drivers Penn ESE370 Fall DeHon
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