1. The Design Process Applying Value Analysis to Determine an Optimum Solution by Prof. Bitar

2. Abstraction & Synthesis Homework #2 Viable Options Preferred Solution Apply Constraints HW#2 Abstraction & Synthesis Possible Solutions Perform Value Analysis Research Prior Art Brainstorm

3. Window Candle Block Diagram with Two Defined Blocks Solar Cell Charge Controller Rechargeable Battery 1.2V NiCd DC-DC Boost Converter LED 3.2V 20mA Flickering Control Mode Selection Photo Sensor

4. Agilent White LED Spec. Sheet

5. LED Specifications – Curves ! Max. Forward Current vs. Voltage Check: 20mA @ 3.2V (Typical)

6. Battery Specifications

7. Battery Specification Discharge Curve

8. DC-DC Boost Converter Interface Specs INPUT: 1.2V(Nominal) Minimum ?(0.8V) Maximum ?(1.6V) OUTPUT: 20mA (constant current?) 3.2V (Nominal for White) 1.7V (Nominal for Red)

9. Searching for Possible Boost Converters… www.digikey.com – –DC-DC Converters (4,561 IN STOCK!) Narrowing Search (down to 47) – –Step-Up (Boost) – –Vmin ≤ 0.8V (why?) – –Internal Switch – –Number of Outputs (1) – –Small Qty. Packaging (cut tape / tube) Case…

10. Package/Case Concerns… For prototypes, through-hole packages (8- DIP, 16-Dip, etc.) are easiest to work with. If chip is only available in surface-mount, avoid DFN, QFN, LLP and BGA packages since pins are underneath. For surface-mount ic’s, try to get largest packages possible with gull-wing pins.

11. Possible Manufacturers ManufacturerPart NumberUnit Linear TechnologyLTC3429ES6#TRMPBF$4.56 Maximum Integrated Products MAX1724EZK50+T$3.63 Texas InstrumentsUCC3941DTR-3$3.89 National SemiconductorLM2623MM/NOPB$2.91 ST MicroelectronicsL6920DB$2.07

12. Also Ran Across Another Device! LED Driver IC’s… www.digikey.com – –LED Drivers (1,319 IN STOCK!) Narrowing Search (down to 47) – –Step-Up (Boost) – –Vmin ≤ 0.8V (why?) – –Internal Switch – –Number of Outputs (1) – –Small Qty. Packaging (cut tape / tube) Case…avoid DFN, QFN, LLP, BGA

13. Possible LED Drivers ManufacturerPart NumberUnit Linear TechnologyLTC3490ES8#PBF$4.20 LT1932ES6#TRMPBF$4.17 Diodes/ZetexZXLD383ET5CT-ND$1.56

14. IC’s Making the First Cut (Just based on PRICE!) ManufacturerPart NumberUnit National Semiconductor DC-DC ConverterLM2623MM/NOPB$2.91 ST Microelectronics DC-DC ConverterL6920DB$2.07 Diodes/ZetexLED DriverZXLD383ET5CT$1.56

15. National - LM2623

16. Typical Application Circuit (Constant Voltage Output)

17. Note External Components… InductorCapacitor(s) Schottky Diode Resistive Divider

18. ST - ST - L6920DB

19. Typical Application Circuit (Note Fewer External Components!)

20. Diodes/Zetex - ZXLD383ET5CT

21. Typical Application Circuit

22. Leaning Toward the Diodes/Zetex LED Driver http://www.diodes.com/datasheets/ZXLD3 83.pdf http://www.diodes.com/datasheets/ZXLD3 83.pdfPro’s –Price –Ease of Use (Few External Components) –Designed for My Application Con’s –Single Manufacturer (Not Multiple Source!)