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EE241 Final Project High Speed Sense Amplifier With Offset compensation for SRAMs Yida Duan

EE241 Final Project High Speed Sense Amplifier With Offset compensation for SRAMs Yida Duan. Motivation & Proposed Solution. Problem (Offset). Time Margin needed for input to grow > offset Response Time = Time Margin + Sense Time

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EE241 Final Project High Speed Sense Amplifier With Offset compensation for SRAMs Yida Duan

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  1. EE241 Final Project High Speed Sense Amplifier With Offset compensation for SRAMs Yida Duan

  2. Motivation & Proposed Solution Problem (Offset) • Time Margin needed for input to grow > offset • Response Time = Time Margin + Sense Time • Time Margin is large for large offset (offset compensation) Solution (offset Compensation)

  3. Basis of Comparison (b) Clamped-bitline current sense amp (CSA) (a) Conventional Voltage Sense amp (VSA) (d) Non-strobed regenerative voltage sense amp (NSR-VSA) (c) Offset-compensated current sense amp (OCCSA)

  4. Conventional Voltage Sense Amplifier Reset Phase Sense Phase • Good: • No Reset Power • Bad: • Complete bitline discharge • Large Sense Time (Bitline loading) • Large Offset

  5. Clamped-bitline Current Sense Amp Reset Phase Sense Phase

  6. Clamped-bitline Current Sense Amp Between the 2 phases • IM7 > Ios prior to regeneration • IM7 saturates at Iin/2 for large Time Margin • M7 in linear region, RM7 is small IM7

  7. Clamped-bitline Current Sense Amp – Offset Calculation Assume , Because • To convert Ios to Vos, Vos=RM7Ios • Offset is mainly due to M1—M4

  8. Clamped-bitline Current Sense Amp • Good: • Bitline clamped to a high voltage after sense phase • Small Sense time (No bitline loading) • Bad: • Reset power • large offset, need Time Margin • Will not work if Iin < Ioffset

  9. Offset-Compensated Clamped-bitline Current Sense Amplifier • Same Operation as clamped bit line current sense amplifier • Virtually no offset (any offset is sampled on 4fF caps)

  10. Non-strobed Regenerative Voltage Sense Amplifier Reset Phase Sense Phase • Good: • No bitline loading • No Time Margin • Bad: • Reset power • Larger area • Compromise robustness

  11. Simulation Results – Sense Time

  12. Simulation Results - Offset Avg=992.9mV σ=46.2mV

  13. Simulation Results - Yield

  14. Simulation Results – Response Time Avg=57.5ps σ=1.5ps Avg=120ps σ=4.5ps

  15. Conclusion & Performance Summary • OCCSA is 30X faster than VSA, 2X faster than NSR-VSA • OCCSA has comparable reset power with NSR-VSA • OCCSA has comparable area with NSR-VSA Note: Time Margin Uncertainty is not considered

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