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Low Voltage Power Delivery to FPGA For JWST

Low Voltage Power Delivery to FPGA For JWST. By Jack Shue Code 563. Power Requirements For ICDH. 5v (4.75v to 5.25v) 6a 50mv ripple 3.3v (3.13v to 3.46v) 20a 30mv ripple 1.5v (1.42v to 1.57v) 6a* 15mv ripple 1.5v is the one to be talked about. * Original requirement was 25a.

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Low Voltage Power Delivery to FPGA For JWST

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  1. Low Voltage Power Delivery to FPGAFor JWST By Jack Shue Code 563

  2. Power Requirements For ICDH • 5v (4.75v to 5.25v) 6a 50mv ripple • 3.3v (3.13v to 3.46v) 20a 30mv ripple • 1.5v (1.42v to 1.57v) 6a* 15mv ripple 1.5v is the one to be talked about * Original requirement was 25a.

  3. I2R Problems for 1.5v Maximum allowable drop 15mv 6a PC Board (Backplane) LOAD FPGA 1.5v Converter V=IR R=V/I R=0.015/6 R<2.5mW Rorg<0.6mW

  4. Study of Voltage Drop Across Copper Grid Moving Probe Point Fixed Probe Point Copper Plate 4 amp Load 4 amp Load 4 amp Load 4 amp Load 4 amp Load Grid Moving Probe Point Fixed Probe Point Extra 5 Copper Wires

  5. Voltage Contour Map 2” wide 2 oz copper 20mv delta 2” wide 2 oz copper with 5 #20 awg wires 14mv Delta 2mv /color

  6. Same Problem Different Scale 8 Generators 1.2MW each = 9.6MW total Assume all power goes out on 1 line. Current Out =19.2 amperes ICDH PDU 1.5 volt Output Current = 25 amperes Bottom line, Power Companies go to High Voltages to reduce line loss

  7. Power Rule of Thumb In a power distribution system current levels should never be greater than the voltage of the system. i.e. 32 volt bus 32 amp max 1024 watts 1.5 volts 1.5 amp max 2.25 watts

  8. What To Do About Line Losses? • Go to higher voltages • Use more copper • Get power supply closer to load • Split load

  9. What To Do About Line Losses? • Go to higher voltages • for as long as you can and then drop to the correct voltage using converters and regulators • Use more copper • More Layers on PC Board • More Vias • More Pins on Connectors

  10. What To Do About Line Losses? • Get power supply closer to load • More Capacitors close to load for transients • The closer a supply is to load the less copper is needed • Lower Copper Loss • Lower impedances (inductive loss) • Split load • Less demand on each supply (more supplies) • Effectively more copper • Allows for different PC Boards

  11. Choice of Small Converters(General Options) • Linear Regulator • Low Dropout Regulator • Standard Linear Regulator • Pulse Width Modulated • Isolated Output Converter • Common Ground Converter

  12. Choice of Small Converters(Efficiency) • Linear Regulator Efficiency efficiency% = Vout/Vin * 100 • Pulse Width Modulated Efficiency efficiency% = Pout / Pin * 100

  13. Buck Switcher 5v to 1.5v Linear 2.5v to 1.5v

  14. Choice of Small Converters • Linear Regulator • Low Dropout Regulator • None Rated for Spaceflight • Standard Linear Regulator • Low efficiency due to voltage drop of over 3 volts at 2a. (6 watt minimum loss per regulator) * Note: Off the Shelf Linear Regulators are designed to run off of their input voltage.

  15. Buck Switcher 5v to 1.5v Linear 2.5v to 1.5v

  16. Choice of Small Switching Converter • Pulse Width Modulated • Isolated Output Converter • Isolation required? • Tend to be larger than Linear regulators due to transformer and filtering required for PWM converters • Has an output ripple (Capacitor ESR dependant) • Efficiency may or may not be better than Linear Regulator • Common Ground Converter (Buck) • Can be made smaller than isolated converter • Has an output ripple (Capacitor ESR dependant) • Efficiency may or may not be better than Linear Regulator

  17. Buck Switcher 5v to 1.5v Linear 2.5v to 1.5v

  18. What is Industry Doing? • Using Low Dropout Linear Regulators • Using Buck Regulators The break point as to what to use is at about the 2 ampere load point For the commercial world there are many vendors making both low dropout regulators and PWM converters. Some meet some military specifications, but, unfortunately none are being made for spaceflight conditions.

  19. Power Generator What is Industry Doing? Sub Station House Load 500,000v 13,000v 120v 12v

  20. Power Distribution Box Load Power Generator Solar Arrays ≈60v 32v 2.5v 1.5v So What is JWST ICDH Doing?

  21. So What is JWST ICDH Doing? • Drivers • Ripple, regulation, and response time • Internal Power Consumed • Spaceflight Parts and Radiation • Size

  22. So What is JWST ICDH Doing? • Drivers • Ripple, regulation, and response time • All point to some form of linear regulator, Off the Shelf or designed here to meet requirements. • Internal Power Consumed • Low drop off linear regulator vs. Switcher almost the same for internal power • Spaceflight Parts and Radiation • No low drop out linear regulator available for space flight. • Parts available for design • Hybrid converters are not available in class K level parts.

  23. So What is JWST ICDH Doing? • Pick • Home Built Low Dropout Linear Regulator driven from a low voltage power bus with control power coming from analog ±12v line ±12 volt line allows internal parts to operate without having to generate voltages internally . The linear regulator is also quieter and can be duplicated near its load.

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