Thiết kế VLSI - Bài 6 (HUST) Thầy Nguyễn Vũ Thắng

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goupee.vn goupee.com Design and Implementation of VLSI Systems Lecture06 PERFORMANCE ESTIMATION cuu duong than cong . com fb.com/goupee.vn CuuDuongThanCong.com https://fb.com/tailieudientucntt

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goupee.vnPower in circuit element goupee.com cuu duong than cong . com fb.com/goupee.vn CuuDuongThanCong.com https://fb.com/tailieudientucntt

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goupee.vnPower in circuit element goupee.com cuu duong than cong . com fb.com/goupee.vn CuuDuongThanCong.com https://fb.com/tailieudientucntt

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goupee.vnSource of power dissipation goupee.com • Power dissipation in CMOS circuits comes from two components: • Dynamic dissipation due to • charging and discharging load capacitances as gates switch • “short-circuit” current while both pMOS and nMOS stacks are partially ON • Static dissipation due to • subthreshold leakage through OFF transistors • gate leakage through gate dielectric • junction leakage from source/drain diffusionscuu duong than cong . com • contention current in ratioed circuits fb.com/goupee.vn CuuDuongThanCong.com https://fb.com/tailieudientucntt

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goupee.vnSource of power dissipation goupee.com cuu duong than cong . com fb.com/goupee.vn CuuDuongThanCong.com https://fb.com/tailieudientucntt

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goupee.vnCharging a capacitor goupee.com cuu duong than cong . com fb.com/goupee.vn CuuDuongThanCong.com https://fb.com/tailieudientucntt

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goupee.vnSwitching waveforms goupee.com cuu duong than cong . com fb.com/goupee.vn CuuDuongThanCong.com https://fb.com/tailieudientucntt

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goupee.vnSwitching power goupee.com cuu duong than cong . com fb.com/goupee.vn CuuDuongThanCong.com https://fb.com/tailieudientucntt

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goupee.vnActivity factor goupee.com cuu duong than cong . com fb.com/goupee.vn CuuDuongThanCong.com https://fb.com/tailieudientucntt

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goupee.vnShort circuit currents goupee.com cuu duong than cong . com fb.com/goupee.vn CuuDuongThanCong.com https://fb.com/tailieudientucntt

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goupee.vnPower dissipation sources goupee.com cuu duong than cong . com fb.com/goupee.vn CuuDuongThanCong.com https://fb.com/tailieudientucntt

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goupee.vnDynamic power breakup goupee.com cuu duong than cong . com fb.com/goupee.vn CuuDuongThanCong.com https://fb.com/tailieudientucntt

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goupee.vnDynamic power example goupee.com Example: A digital system-on-chip in a 1 V 65 nm process (with 50 nm drawn channel lengths and Q= 25 nm) has 1 billion transistors, of which 50 million are in logic gates and the remainder in memory arrays. The average logic transistor width is 12 Q and the average memory transistor width is 4 Q. The memory arrays are divided into banks and only the necessary bank is activated so the memory activity factor is 0.02. The static CMOS logic gates have an average activity factor of 0.1. Assume each transistor contributes 1 fF/μm of gate capacitance and 0.8 fF/μm of diffusion capacitance. Neglect wire capacitance for now (though it couldcuu duong than cong . com account for a large fraction of total power). Estimate the switching power when operating at 1 GHz. fb.com/goupee.vn CuuDuongThanCong.com https://fb.com/tailieudientucntt

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goupee.vnDynamic power reduction goupee.com cuu duong than cong . com fb.com/goupee.vn CuuDuongThanCong.com https://fb.com/tailieudientucntt

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goupee.vnActivity factor goupee.com • The activity factor is a powerful and easy-to-use • Turn off a circuit => activity factor and dynamic power go to zero. • Blocks turned off by stopping the clock => clock gating. • When a block is on, the activity factor is 1 for clocks • The activity factor of a logic gate can be estimated by calculating the switching probability. cuu duong than cong . com fb.com/goupee.vn CuuDuongThanCong.com https://fb.com/tailieudientucntt

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goupee.vnClock gating goupee.com cuu duong than cong . com fb.com/goupee.vn CuuDuongThanCong.com https://fb.com/tailieudientucntt

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goupee.vnActivity factor estimation goupee.com Switching Probability: • Activity factor of a node is the probability that it switches from 0 to 1. • This probability depends on the logic function. • Analyze probability that each node is 1 => can estimate the activity factors cuu duong than cong . com fb.com/goupee.vn CuuDuongThanCong.com https://fb.com/tailieudientucntt

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goupee.vnActivity factor estimation goupee.com cuu duong than cong . com fb.com/goupee.vn CuuDuongThanCong.com https://fb.com/tailieudientucntt

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goupee.vnSwitching probability goupee.com cuu duong than cong . com fb.com/goupee.vn CuuDuongThanCong.com https://fb.com/tailieudientucntt

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goupee.vnExample goupee.com cuu duong than cong . com fb.com/goupee.vn CuuDuongThanCong.com https://fb.com/tailieudientucntt

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