EE6361: Advanced Topics in VLSI (Jan 2019)

• Janakiraman Viraraghavan (IITM)
• Dr. Rahul Rao (STSM IBM. India. Pvt. Ltd)

ESB-213B

T-slot - Friday (2:00 - 4:50 PM)

• Assignments: 10%
• Mid Term: 30%
• Project : 20%
• End Semester Exam: 40%

(Why we teach this course?)

• Introduce students to some relevant advanced topics of current interest in academia and industry
• Give the students a feel for research topics
• Make students aware of work happening in industries, specifically in India

This course will cover three broad subjects:

1. SRAM design (Rahul Rao)
2. Embedded DRAM design (Janakiraman)
3. Emerging memories (PCM/ STT RAM) (Rahul + Janakiraman + Guest lecture)

(What the students should be able to do after the course)

• Articulate memory hierarchy and the value proposition of SRAMs in the memory chain + utilization in current processors
• Explain SRAM building blocks and peripheral operations and memory architecture (with physical arrangement)
• Articulate commonly used SRAM cells (6T vs 8T), their advantages and disadvantages
• Explain the operation of a non-conventional SRAM cells, and their limitations
• Explain commonly used assist methods
• Explain how variations impact memory cells

• Explain the working of a (e)DRAM and what Embedded means?
• Explain the working of a feedback sense amplifier and modify existing designs to improve performance
• Calculate the voltage levels of operation of various components for an eDRAM
• Introduce stacked protect devices to reduce voltage stress of the WL driver

• Memory hierarchy
• Memory organization
• Flip flop
• 6T SRAM basics

• 6T SRAM cell
• Static/ Read and Write noise margins
• Read/ Write/ Hold and Access failures
• Column interleaving

Lecture Slides

• Alternative Cell Types

1. Split word line with single ended read
2. Assymetric cells
3. Decouple Read/Write Cells (8T Cells)
4. Regenerative Feedback

• Impact of Variation

Lecture Slides

• Redundancy
• Modes of failure
• Assist Circuits

Lecture Slides

• BTI Stress
• Memory Testing
• Power

Lecture Slides

• Variation characterization

Lecture Slides

• Variation characterization (continued …)

Lecture Slides

• Course project description - In Memory Computing

• Basics of DRAM
• Definition of Embedded
• Requirement for short BLs in DRAMs
• Transfer ratio
• Retention time/ Refresh rate analysis
• Power supplies required for eDRAM
• Advantages of eDRAM over eSRAM

In class Quiz

eDRAM Lecture Slides (2018)

• Write time calculation
• Hierarchical sensing
• 3T Micro Sense Amp
• Micro Sense Amp Evolution

Barth, J. et al., “A 500 MHz Random Cycle, 1.5 ns Latency, SOI Embedded DRAM Macro Featuring a Three-Transistor Micro Sense Amplifier,” IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 43, NO. 1, JANUARY 2008. PDF

In class quiz

SRAM based In Memory Compute circuit design to implement the Multiply Accumulate Operation

1. A. Biswas and A. P. Chandrakasan, “CONV-SRAM: An Energy-Efficient SRAM With In-Memory Dot-Product Computation for Low-Power Convolutional Neural Networks,” in IEEE Journal of Solid-State Circuits, vol. 54, no. 1, pp. 217-230, Jan. 2019. doi: 10.1109/JSSC.2018.2880918
2. M. Kang, S. K. Gonugondla, A. Patil and N. R. Shanbhag, “A Multi-Functional In-Memory Inference Processor Using a Standard 6T SRAM Array,” in IEEE Journal of Solid-State Circuits, vol. 53, no. 2, pp. 642-655, Feb. 2018. doi: 10.1109/JSSC.2017.2782087

• Read time calculation
• SOI Technology - Floating body effects on eDRAM
• Gated Feedback Sense Amplifier

G. Fredeman et al., “A 14 nm 1.1 Mb Embedded DRAM Macro With 1 ns Access,” in IEEE Journal of Solid-State Circuits, vol. 51, no. 1, pp. 230-239, Jan. 2016. doi: 10.1109/JSSC.2015.2456873 PDF

In class quiz

• Variability study
• Thick Oxide Word-line drivers
• Thin Oxide Word-line drivers

In class quiz

• Redundancy and Testing
• Non Volatile Memories
• Charge Trap Transistor

In class quiz

Balaji Jayaraman, Derek Leu, Janakiraman Viraraghavan, Alberto Cestero, Ming Yin, John Golz, Rajesh R. Tummuru, Ramesh Raghavan, Dan Moy, Thejas Kempanna, Faraz Khan, Toshiaki Kirihata, Subramanian Iyer 80Kb Logic Embedded High-K Charge Trap Transistor based Multi-Time-Programmable Memory with no Added Process Complexity J. Solid State Circuits,53(3): 949-960 (2018) PDF

eNVM Lecture Slides