MCP Nanoscale IC Developers

1. Senior Design Expo 04/27/2012 MCP Nanoscale IC Developers Kenneth Corbett Endowment

2. Problem Definition • Design an optical communication Integrated Circuit (IC) chip that will allow full-duplex transmission of wireless data at a bandwidth of 100kbit/s over a distance of several meters using a Field Programmable Gate Array (FPGA) interface.

3. MCP Nano Design Team • Undergraduate Seniors pursuing a B.S.E.E. Markus Geiger Chris Goodale Pin-Jen Wang

4. Consulting Faculty • Consulting Faculty Dr. Ken Noren Dr. Suat Ay

5. Presentation Outline • Product applications • Technical constraints and design goals • Simplified block diagram • General design considerations • Major design decisions • Integrated Circuit Design • FPGA interface • Final Product • Demonstration platform • Specifications • Project cost • Future work • References

6. Product Viability & Applications • Directional, highly secure wireless transmission • Control/monitor sensitive information/infrastructure eg. wireless traffic monitoring, wireless money transfer via cellphone, etc. • Alternative to WiFi(Wireless Fidelity), which is based on the IEEE 802.11 standard • Electro Magnetic (EM) safe • Unregulated wireless spectrum • Wireless sensor networks

7. Technical Constraints • Transmitter (TX) requirements • Pdp_max = 500mW • V_bias = 1.5V (+/- 100mV) • Receiver (RX) requirements • Pdp_typ = 100mW • V_bias = -5V • Transmission distance through air • limited by power output of light-emitting diode (LED) and beam half angle • Power decreases through air with

8. Design Goals • Preliminary Specifications: • 100kbit/s signal transmission • Range of 2+ meters • Custom transmission protocol • Total power dissipation of TX circuitry < 500mW • Total power dissipation of RX circuitry < 10mW • 5V single-ended power supply

9. Simplified Block Diagram Receiver High gain trans impedance amplifier (TIA) Photo sensitive element (receiver) Comparator to digitize the signal Encoder that processes the received signal Free space User user interface Decoder that processes binary input according to a communication standard Transmitter Light emitting element (transmitter) Common Drain amplifier to provide sufficient current MCPnano Transceiver IC FPGA

10. General Design Considerations • Off the shelf components • LED to transmit data (IR or visible light) • Photo-diode to receive data (PIN or Avalanche) • MCPnano Integrated Circuit (IC) Design • Amplifier / Comparator stages for the receiver circuit • Transmitter circuitry consisting of repeaters and FET • System integration/interface with FPGA • Connectivity/User-interface • Encoding/Decoding schemes

11. Decisions: LED Infrared (IR) LED Visible Light LED Wavelength: 390nm to 780nm Very susceptible to interference from ambient light (need for a versatile filter system & noise cancellation system) May use solid-state lighting (more compact system, ease of deployment) • Wavelength: 780 nm to 950 nm • limits interference due to ambient light • Need for separate transmission circuitry • Vishay High Speed IR LED 890nm:

12. Decisions: Receiver fff Photo transistor PIN Photo-diode Slow response time (~500ns+ rise & fall) Not feasible for our com. System Inherent gain of the NPN transistor Low cost (50c/piece) Fast rise/fall times (5 to 50ns typ.) 5V typ. rev. bias Low cost (eg. 50c/piece) Osram Photo diode 900nm Fast rise/fall times (1ns typ.) Highly sensitive High gain (self multiplication ‘avalanche’ mechanism) 40V typ. rev. bias High cost ($50+/piece) Avalanche Photo-diode

13. Spectral Response Matching PIN Photodiode IR LED

14. Integrated Circuit (IC) design • Design environment: Cadence 6.1.5 • Process: ONSemi’s 0.5mm process (C5) • Tapeout Date: November 28th, 2011 • Cost:$960 • IC Design Effort • Receiver design (TIA, comparator) • Transmitter design (LED driver)

15. IC Design considerations • Bias voltages to be set externally (adjustability) • Allows use of different diodes • Debugging • Feedback resistor/potentiometer located off chip • impractical to implement 5MOhm resistor on-chip • Flexibility, various distances possible • Reference current set through off-chip variable resistor (adjustable gain of opamp if needed)

16. Integrated Circuit (IC) Schematic

17. Integrated Circuit (IC) Micrograph

18. Dual Inline Package (DIP-40)

19. FPGA interface • Custom VHDL code that implements the following protocol

20. BASYS2 FPGA board • Special Thanks to Dr. James Frenzel (aka Dr. J) for supplying us with two Digilent BASYS2 boards

21. Final Product back front

22. Demonstration platform

23. Transmission of letter A (“00011100”)

24. Specifications • Specifications: • 100kbit/s signal transmission • Maximum range of 3 meters • Custom transmission protocol (FPGA in VHDL) • Total power dissipation of TX < 500mW • Total power dissipation of RX < 10mW • 5V single-ended power supply (battery pack)

25. Project Deliverables • Compact IC transceiver unit on a PCB • Datasheet/Documentation of transceiver • TX: LED • RX: Photo-diode • IC: TIA, Comparator, LED driver • Discrete level shifter • Custom Communication Protocol (VHDL)

26. Budget Breakdown

27. Future work • Incorporate the transmission protocol (using shift registers, etc.) onto the Integrated Circuit • VHDL description may be used to create the layout using automated place & route tools • Improve the comparator design on the IC (accomplish hysteresis) • Design for higher speed transmission (500kbit/s +)

28. Reference Information • FSO applications / outlook into the future • http://www.bu.edu/smartlighting/files/pdf/May808_slides_Little_FSO_Commun1.pdf • IR vs. RF • https://www.audiolinks.com/articles/rfvsir/ • Vishay High Speed IR LED 890nm: • http://www.mouser.com/Search/ProductDetail.aspx?qs=%2fjqivxn91cfAnyW9i5Zlpg%3d%3d • Osram Photo diode 900nm: • http://www.mouser.com/ProductDetail/Osram-Opto-Semiconductor/SFH-2500-FA-Z/?qs=K5ta8V%252bWhtarQtPwL45qKw%3d%3d