Wide Vin DC/DC Converters: Reliable Power for Demanding Applications

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Wide Vin DC/DC Converters: Reliable Power for Demanding Applications

  1. 1. Wide Vin DC/DC Converters: Reliable Power for Demanding Applications
  2. 2.  This webinar will be available afterwards at www.designworldonline.com & email  Q&A at the end of the presentation  Hashtag for this webinar: #DWwebinar Before We Start
  3. 3. Moderator Presenter Mary Gannon Design World Jim MacDonald Texas Instruments
  4. 4. Wide Vin DC/DC Converters Reliable Power Solutions for Demanding Applications
  5. 5. • Wide Vin DC/DC converter overview • Wide Vin power for Industrial systems • Wide Vin power for Automotive systems • Wide Vin power for Communications systems • Additional Wide Vin resources Agenda
  6. 6. TI’s Wide Vin DC/DC Converter Products Reliable Power Solutions for Demanding Applications Applications Power Challenges Products Industrial 12V, 24V & higher Bus Voltages Automotive & Transportation 12V/24V off-battery systems Communications 24V/48V battery-backed systems Multiple Input Sources Varying Input Voltages Large transients and/or noisy & harsh conditions Boost and Buck-boost Controllers and Regulators Buck Controllers & Regulators Integrated Power Modules
  7. 7. Vin (V) 100V 80V 60V 40V 20V Commercial Auto Consumer Auto Mass Transit (Busses, Trains) Avionics & Defense Factory Automation BTS Repeaters Base Stations Networking & Storage Automotive Industrial Comms & Cloud 10V 12V 24V 24V 28V 24V 24V 48V 48V Nominal bus voltage Bus operating range Potential transient range Auto start-stop range 4-20mA loop range Wide Vin Benefit: Optimized for Use Across Multiple Markets and Applications
  8. 8. Vin (V) 100V 80V 60V 40V 20V Commercial Auto Consumer Auto Mass Transit (Busses, Trains) Avionics & Defense Factory Automation BTS Repeaters Base Stations Networking & Storage Automotive Industrial Comms & Cloud 10V 12V 24V 24V 28V 24V 24V 48V 48V Nominal bus voltage Bus operating range Potential transient range Auto start-stop range 4-20mA loop range Wide Vin Benefit: Optimized for Use Across Multiple Markets and Applications
  9. 9. Vin (V) 100V 80V 60V 40V 20V Commercial Auto Consumer Auto Mass Transit (Busses, Trains) Avionics & Defense Factory Automation BTS Repeaters Base Stations Networking & Storage Automotive Industrial Comms & Cloud 10V 12V 24V 24V 28V 24V 24V 48V 48V Nominal bus voltage Bus operating range Potential transient range Auto start-stop range 4-20mA loop range Wide Vin Benefit: Optimized for Use Across Multiple Markets and Applications
  10. 10. Wide Vin Benefit: High Voltage Rating Eliminates Protection Circuits & Saves PCB Area VIN DC/DCVIN_BAT RTN VIN DC/DC VIN_BAT RTN VIN Wide Vin DC/DC VIN_BAT RTN Transient Absorbers Disconnect FET Wide Vin DC-DC Pro: • Does not interrupt dc/dc power during OV transients Pro: • Not dissipative OV protection. Can survive for longer duration OV conditions. Pro: • Automatic OV protection up to 65V/75V • Operation not interrupted in OV condition • No extra design work required. Cons: • Selection can be complicated; Dependent on energy (Volt/time) • Dissipates energy (bigger size) • Longer duration OV (e.g. ISO 7637 Pulse 5b) conditions not taken care of in reasonable size/cost Cons: • Needs multiple components including a disconnect FET. • Creates voltage drop (power dissipation) in normal operation. • PMOS tends to be bigger. NMOS needs charge pump. • Interrupts power flow during OV Cons: • May exhibit slightly lower efficiency when operating from lower input voltages such as 3.3V and 5V
  11. 11. Wide Vin Power for Industrial Systems
  12. 12. Challenge #1: Designing a Reliable & Low Cost System Bias Supply System Bias Supply Digital Isolator • The system bias rail(s) must be derived from the system backplane, which is typically 24V but can experience transients of 40V or higher • Isolation is often required for noise immunity or safety • The use of opto-isolators is often avoided due to reliability Industrial Automation Equipment System Need: Application Challenges: • Most systems require a low current bias supply for the micro-controller and/or FPGA to initiate system start-up correctly each time
  13. 13. Wide Vin Bias Supply System Examples 36-75Vin Vout LM5112LM5017 9VPRI 9VSEC Digital Controller UCD3138 LM5101 LM5017 Flybuck SW1 SW1 M DR_HS DR_LS -VEE +VCC -VEE +VCC Vin Isolated bias supply for DC/DC power modules Isolated bias supply for IGBT-based AC motor drives Multi-output bias supply for PLC I/O modules
  14. 14. LM5017/8/9 Fly-buck™ Bias Supply ICs + + + + VI N BST RON RTN SW VCC FB UVLO VIN VOUT1 VOUT2 RFB1 RUV1 RON COUT1 CBST D1 CIN COUT2 RFB2 RUV2 X1 Rr NP NSLM5017 CVCC + D2 LM5017 Feature System Benefits 7.5V to 100V operating range Works with all major bus voltages Integrated synchronous FETs High efficiency, fewer components Constant on-time (COT) architecture No loop compensation needed 100/300/600mA current rating Addresses bias needs up to ~6W Switching frequency up to 1MHz Reduces PCB footprint Ultra-fast transient response Fewer output capacitors needed Isolated bias w/ no opto-isolator Higher reliability, fewer components + + + VIN BST RON RTN SW VCC FB VIN VOUT RFB1 Rr RUV1 RON COUT CBST CIN RFB2 RUV2 L UVLO + CVCC LM5017 Input Voltage (V) MaxOutputCurrent(mA) 10048 LM5017LM25017 LM5018LM25018 LM5019LM25019 7.5 100 300 600 Synchronous Buck Circuit Small & efficient bias supply from a 24V or 48V input bus Isolated Fly-buck Circuit Ideal for isolated and multi-output bias supplies; no opto needed!
  15. 15. Fly-buck Isolated Bias Supply Basics Flybuck Buck + -Vin Vout Vin Vpri Vsec 1 N • The Fly-buck converter is evolved from a synchronous buck converter by adding coupled windings to the inductor to have flyback-like isolated outputs. • The isolated outputs can be multiple by adding more secondary windings to the transformer • A simple and low part count solution for multi-output/isolated power supply design
  16. 16. Flybuck Flyback Outputs Multiple isolated and one non-isolated Isolated outputs can be negative Same capabilities Input Range Vin-min must be > primary output Vin-min smaller or larger than Vout Size Smaller solution, smaller transformer Cost Fewer component count, lower cost Transformer 2-winding transformer 3-winding transformer larger and more expensive FET Switch Stress Vin Vin + Vout/N Performance Good regulation achievable, 5% on both primary and secondary outputs Similar regulation through tertiary winding. High output accuracy using opto, but large deviation under light load condition Fly-buck vs. Flyback Solution Comparison: Summary • The Fly-buck can provide a simple, small and cost effective power solution making it a suitable flyback alternative
  17. 17. • The Fly-buck can provide a simple, small and cost effective power solution making it suitable as a flyback alternative (typically) • A Fly-buck vs. Flyback Comparison: o Spec: Nominal Vin=24V, Vo1=12V, Vo2=-12V, 250mA max load on each output Fly-buck  1:1 single secondary winding transformer  Primary side regulation  Primary: 12V, non-isolated  Secondary: -12V, isolated Flyback  1:1:1 two secondary windings transformer  Secondary side regulation through opto-coupler  Secondary: +/-12V, isolated Fly-buck vs. Flyback Solution Comparison: Case Study
  18. 18. Fly-buck vs. Flyback Solution Comparison: PCB Design LM5017 Flybuck  Component Count 23  Effective Area 1.4x1.2 inch  Max height: 8mm LM5000 Flyback  Component Count 45  Effective Area 1.8x1.8 inch  Max height: 10mm Fly-buck offers a smaller solution size vs. Flyback Fly-buck uses fewer components than the Flyback, and no opto-isolator is needed. Effective Area Effective Area
  19. 19. Fly-buck vs. Flyback Solution Comparison: Performance LM5017 Flybuck 10.600 10.800 11.000 11.200 11.400 11.600 11.800 12.000 0.000 0.050 0.100 0.150 0.200 0.250 Vo(V) Io1=Io2 (A) Vo1 -Vo2 Vo2 has an additional diode drop, and the delta grows bigger at higher load 4%Δ 11.600 11.700 11.800 11.900 12.000 12.100 0.000 0.050 0.100 0.150 0.200 0.250 Vo(V) Io1=Io2 (A) Vo1 -Vo2 LM5000 Flyback Vo2 is lower at light load, but it can be improved by adding pre-load 78.1% 83.8% 86.4% 87.7% 87.9% 73.3% 81.5% 84.5% 86.2% 87.1% 70.0% 75.0% 80.0% 85.0% 90.0% 0.000 0.050 0.100 0.150 0.200 0.250 Efficiency Io1=Io2 (A) Flybuck Flyback +2% Vo1 and Vo2 are equally loaded from 0A to 250mA Flybuck can achieve +/-5% accuracy under balanced load, and has slightly higher efficiency than Flyback
  20. 20. Challenge #2: Designing a Boost Supply with Overload Protection Traditional boost solutions: • Require fuse and/or hotswap controllers to protect against inrush or over-current faults • Fuses require system service after a fault • Interaction between ICs must be considered Hot swap controller Boost controller Load Optional fuse SUPPLY Boost controller w/ disconnect switch Load Boost with Disconnect Switch: • Limits inrush current during start-up and overloads • Eliminates the need for hot swap controllers • Disconnects the load during catastrophic faults • Avoids unnecessary fuse replacements • Reduces system cost & footprint System Need: Application Challenges: SUPPLY • Ability to power motors without reducing system reliability • Boost converters inherently have no overload or short- circuit protection (current can flow from input to output
  21. 21. System Examples Where Load Disconnect is Needed DC/DC LM5121 24V@2A 12V Supply Print Motor Point-of-sale systems Currency handler Industrial injection molding machine
  22. 22. LM5121 Synchronous Boost Controller with Disconnect Switch VCC LM5121 CSN DG SYNCIN/RT RES SSUVLO VIN AGND BST MODE PGND SLOPE COMP FB HO LO SW + DS VOUTVSUPPLY CSP Disconnect Switch LM5121 Feature System Benefits Wide input voltage range: 4.5V to 65V Output voltage: adjustable up to 100V Supports high voltage input and output with no external protection circuitry needed Synchronous operation High efficiency, bypass operation (Vout = Vin) Load disconnect FET Input to output isolation during shutdown Inrush current limit Avoid unnecessary input fuse replacements Hiccup mode over-current protection Protects against temporary over-load faults Circuit breaker function Disconnects catastrophic faults from input VOUT VIN The disconnect FET enabled a back-to-back MOSFET connection that isolates the load from the source during output fault conditions and eliminates the need for a fuse LM5121 Eval Board with input disconnect FET
  23. 23. + - CS AMP A=10 RS Circuit Breaker Comparator 1.6V/0.11V + - LM5121 + VIN CSP CSN DG DS Disconnect Switch Sense Resistor • If the voltage across the sense resistor exceeds the circuit breaker threshold (~160mV), the internal comparator and FET will quickly turn off the external disconnect FET • When the sense resistor voltage drops below circuit breaker disable threshold (~10mV), the disconnect FET is turned on again Circuit Breaker Function Protects against output short-circuits and other catastrophic faults How does it work?
  24. 24. Challenge #3: Achieving High Power Density and Low EMI System Need: Application Challenges: • High density power circuits that free up valuable PCB real estate for critical system functions • Discrete power ICs require multiple external components and can be complex to design & debug • Integrated DC/DC converter modules can be difficult to manufacture (hidden connections are difficult to inspect) • Power circuits (in general) generate EMI that can degrade performance of sensitive system signals LGA Power Modules • Can be difficult to manufacture (hard to inspect all connections) Discrete DC/DC Converter • More complex design/layout Many systems have minimal PCB area left for the power circuits
  25. 25. LMZ1/2 Power Modules: High Performance and Easy to Design 1A 2A 3A 4A 5A Current 8A 10A LMZ10504 (≈42oC case) Competitors (≈46oC case) Operating Conditions: VIN=5.0V, VOUT=1.8V, IOUT= 4A LMZ13610 6-36Vin, 10A Demo board Fully WEBENCH® enabled for easy design Simulation, thermal analysis, and Easy-to-use leaded packages • Single exposed pad with IC leads • Easy prototyping and manufacturing High PCB Density As few as 5 external components Low Radiated EMI Meets EN55022 Class B Best-in-class Thermal Performance No airflow or heat sink required
  26. 26. Wide Vin Power for Automotive Systems
  27. 27. Challenge #1: Handling the Automotive Battery Range Compliance to load dump and cold cranking requires a wide input range 40V for 12V batteries 60V for 24V battery As low as 3V Automotive battery voltage transients 12V Lead Acid Battery Application Challenges • Battery voltage varies due to engine cranking, load dump, jump starts, and accidental reverse battery connection – Cold crank voltage < 5V – Load dumps cause 40V transients – 24V commercial vehicle load dump transients can exceed 60V Wide Vin power management ICs can increase reliability and reduce system cost
  28. 28. Wide Vin Power Solutions for Automotive Protection Battery conditioning Buck converters PMU Typ 8V, 5V or 3.3V Wide Vin converters & controllers Voltage reference Boost 3V-42V E.g. 10V min boost output Optional reverse polarity or over- voltage/current protection Boost or buck-boost needed if output voltage level must be maintained during cranking Wide Vin buck converter is needed here to survive battery voltage transients Battery: 12 or 24V Standard Vin <28V Wide Vin required ≥28V LDOs
  29. 29. Challenge #2: Dealing with Start-stop • Automotive manufacturers will add Idle start- stop (ISS) capability to increase fuel efficiency • ~15M vehicles will have ISS by 2015 Market Need: Application Challenges: • A start-stop event could push the battery voltage as low as 3V (similar to a warm crank condition) • Vehicles must maintain a stable ~12V output to ensure normal AVN operation despite voltage drops • Must be scalable to address different system needs; <100W for sub-systems up to ≥400W for a centralized voltage stabilizer system for the whole vehicle • Small form factor: must not add significant size or weight to the vehicle or sub-system Voltage Stabilizer Boost 3V-42V E.g. 10V min boost output 12V Battery To power system or sub-system
  30. 30. LM5122: Stackable Synchronous Boost Controller MASTER VCCCSN SYNCIN/RT RES SS UVLO VIN SYNCOUT BST SLOPE COMP FB HO LO SW + VOUT VCCCSN SYNCIN/RT RES SS UVLO VIN BST SLOPE COMP FB HO LO SW VCC SLAVE VSUPPLY VSUPPLY CSP CSP OPT OPT LM5122 Feature System Benefits Wide Vin range: 4.5V to 65V (3V after start-up) Handles load dump and start-stop voltage range Synchronous operation High efficiency, bypass operation (Vout = Vin) Stackable w/ current sharing Scales easily from 1-phase to 8+ phases 100% duty cycle bypass mode Low dropout when not boosting battery voltage Low shutdown current: 9uA Low battery drain when not operating LM5122EV-1PH: 1-phase design for ≤100W PMP7837: 4-phase ref design for 450W Up to 98% Efficiency! Scalable from 1 to 4+ phases! http://www.ti.com/tool/PMP7837 http://www.ti.com/tool/lm5122evm-1ph
  31. 31. Challenge #3: Fitting Wide Vin Power in Tight Spaces Application example: rear-view camera module • Total solution size must fit into tiny space • Operates directly from battery; cold crank down to 4.5V and load-dump up to 42V • High efficiency (low thermal dissipation) • Does not interfere with radio frequency band • Low EMI to avoid degrading video quality The National Highway Traffic Safety Administration will require all vehicles to have a rear-view visibility system starting in May 2018 Market Need: Application Challenges:
  32. 32. Wide Vin Power Solution for Rear-view Cameras DS90UB913A-Q1 Serializer LM34919C 2.9V Buck Converter TPS62231 1.8V Buck Converter RC Filters Aptina AR0132AT Image Sensor 12bit Data & PixCLK, FV, LV Aptina AP0101AT Image Signal Processor (ISP) 10bit Data & PixCLK, FV, LV VDD, IOVDD, IO VAA VDD, IO 2.9V 1.8V 2.8V 12V SMB Conn. Coaxial Cable Power FPD-Link III Serial Data Power/Serializer Board Camera Board Power/Serializer Front Power/Serializer B Camera Board Front Camera Board B Power/Serializer Front Power/Serializer Back Camera Board Front Camera Board Back http://www.ti.com/tool/PMP9300 TI DESIGN: Schematic/BOM/Gerber On line VIN SW BST LM34919C VCC SS RON 4.5V - 40V Input C1 RON R2 R1 C2 VOUT L1 C3 C4 D1 C6 RTN ISEN SGND FB PGD R3PGOOD VDD SHUTDOWN Key Challenge LM34919CQ Benefits Small package size 1.75x2mm uSMD package Wide Vin range 4.5V to 50V input works from battery Low part count Constant on time topology minimizes external components No AM interference 2.6MHz switching frequency Low EMI Meets CISPR 25 Class 5 ~22mm Ultra small package (1.75x2mm)
  33. 33. Wide Vin Power for Communications Systems
  34. 34. Challenge #1: High Current Power From a 48V Bus • Generally constant frequency is desired (for minimizing/managing switching noise) • Potential for high step-down ratios (low duty cycles) • Efficiency and complexity choices (1-stage vs. 2-stage conversion) • Transient response (trying to minimize number of capacitors) • Stability over all operating conditions Creating a high current system supply from a high input voltage (36V or 48V) System Need: Application Challenges: 48V Buck DC/DC Buck DC/DC 28V (PA #1) 24V (Antenna) Isolated Power Module 12V (to uP board) Buck DC/DC 5V/3.3V (Misc)
  35. 35. Selecting the Right Wide Vin Buck Controller High Duty Cycle Low Duty Cycle More stable Fast Transients Current sharing More flexible Benefits: • Inherent feed-forward • Simpler loop compensation Considerations/tradeoffs: • Can be noise sensitive • Not ideal for high Vin to low Vout Benefits: • Inherent feed-forward • Simpler loop compensation • Eliminates leading edge “spike” (excellent for high Vin to low Vout) Considerations/tradeoffs: • Max frequency and duty cycle limits Voltage Mode Benefits: • Good regulation & noise margin • More “tunable” for specific needs Considerations/tradeoffs: • Need feed-forward if Vin can change • Tougher to compensate loop • Current sharing needs extra circuitry Top Parts: TPS40170 TPS40200 Top Parts: TPS43340 TPS43350 Current Mode Constant On-time (or DCAP) Benefits: • Easy to use (no loop compensation) • Fast transient response Considerations/tradeoffs: • Not constant frequency • Not synchronizable • Requires ripple to regulate Top Parts: LM3150 LM5085 Emulated Current Mode Top Parts: LM5116 LM5117 LM5119 LM5008
  36. 36. TI’s Most Popular Wide-Vin Buck Controllers Devices for operation from <60V supply Devices optimized for supplies up to 75V/100V
  37. 37. Part Number Package BVDSS (V) VGS (V) RDS(ON) Typ (10V) (mΩ) RDS(ON) Max (10V) (mΩ) ID @ 25ºC (silicon) Qg(10) Typ (nC) Qgd Typ (nC) Qgs Typ (nC) Qrr - 300A/µs Typ (nC) Coss Typ (pF) Alpha Samples RTM CSD18509Q5B SON5x6 40 20 1.0 1.25 264 160 21.0 34.0 40 1100 30-Jan 14Q2 CSD18502Q5B SON5x6 40 20 1.8 2.3 204 52 8.4 10.3 88 900 Now Now CSD18501Q5A SON5x6 40 20 2.5 3.2 155 42 5.9 8.1 70 725 Now Now CSD18503Q5A SON5x6 40 20 3.4 4.3 145 27 4.3 4.5 52 510 Now Now CSD18504Q5A SON5x6 40 20 5.3 6.6 75 16 2.4 3.2 39 310 Now Now CSD18540Q5B SON5x6 60 20 1.6 2.0 188 58 11.0 12.8 120 498 15-Feb 14Q2 CSD18532Q5B SON5x6 60 20 2.5 3.2 169 44 6.9 10.0 111 470 Now Now CSD18532NQ5B SON5x6 60 20 2.7 3.4 165 49 7.9 16.0 139 495 Now Now CSD18531Q5A SON5x6 60 20 3.5 4.6 134 36 5.9 6.9 100 380 Now Now CSD18533Q5A SON5x6 60 20 4.7 5.9 103 29 5.4 6.6 68 292 Now Now CSD18563Q5A SON5x6 60 20 6.0 7.5 98 29 5.4 6.6 57 292 Now Now CSD18534Q5A SON5x6 60 20 7.8 9.8 69 17 3.5 3.2 54 167 Now Now CSD18537NQ5A SON5x6 60 20 11 14 55 14 2.3 4.7 54 136 Now Now CSD19502Q5B SON5x6 80 20 3.4 4.1 138 48 8.6 14 275 925 Now Now CSD19532Q5B SON5x6 100 20 4.0 4.9 130 48 8.7 13 249 706 Now Now CSD19531Q5A SON5x6 100 20 5.3 6.4 110 37 7.0 11 226 540 Now Now CSD19533Q5A SON5x6 100 20 7.8 9.4 75 27 4.9 7.9 163 395 Now Now CSD19534Q5A SON5x6 100 20 12.4 15.5 53 15 2.7 4.5 97 228 Now 10-Feb 60-100V NexFETs for Wide Vin Controller Applications Ideal for 24V/36V buck designs up to 10A High-side Low-side • Scalable from 40V to 100V • Industry-standard SON 5x6mm package • Ultra-low Qg and Qgd and low thermal resistance Part Number Package BVDSS (V) VGS (V) RDS(ON) Typ (10V) (mΩ) RDS(ON) Max (10V) (mΩ) ID @ 25ºC (silicon) Qg(10) Typ (nC) Qgd Typ (nC) Qgs Typ (nC) Qrr - 300A/µs Typ (nC) Coss Typ (pF) Alpha Samples RTM CSD18509Q5B SON5x6 40 20 1.0 1.25 264 160 21.0 34.0 40 1100 30-Jan 14Q2 CSD18502Q5B SON5x6 40 20 1.8 2.3 204 52 8.4 10.3 88 900 Now Now CSD18501Q5A SON5x6 40 20 2.5 3.2 155 42 5.9 8.1 70 725 Now Now CSD18503Q5A SON5x6 40 20 3.4 4.3 145 27 4.3 4.5 52 510 Now Now CSD18504Q5A SON5x6 40 20 5.3 6.6 75 16 2.4 3.2 39 310 Now Now CSD18540Q5B SON5x6 60 20 1.6 2.0 188 58 11.0 12.8 120 498 15-Feb 14Q2 CSD18532Q5B SON5x6 60 20 2.5 3.2 169 44 6.9 10.0 111 470 Now Now CSD18532NQ5B SON5x6 60 20 2.7 3.4 165 49 7.9 16.0 139 495 Now Now CSD18531Q5A SON5x6 60 20 3.5 4.6 134 36 5.9 6.9 100 380 Now Now CSD18533Q5A SON5x6 60 20 4.7 5.9 103 29 5.4 6.6 68 292 Now Now CSD18563Q5A SON5x6 60 20 6.0 7.5 98 29 5.4 6.6 57 292 Now Now CSD18534Q5A SON5x6 60 20 7.8 9.8 69 17 3.5 3.2 54 167 Now Now CSD18537NQ5A SON5x6 60 20 11 14 55 14 2.3 4.7 54 136 Now Now CSD19502Q5B SON5x6 80 20 3.4 4.1 138 48 8.6 14 275 925 Now Now CSD19532Q5B SON5x6 100 20 4.0 4.9 130 48 8.7 13 249 706 Now Now CSD19531Q5A SON5x6 100 20 5.3 6.4 110 37 7.0 11 226 540 Now Now CSD19533Q5A SON5x6 100 20 7.8 9.4 75 27 4.9 7.9 163 395 Now Now CSD19534Q5A SON5x6 100 20 12.4 15.5 53 15 2.7 4.5 97 228 Now 10-Feb
  38. 38. CSD18563Q5A CSD18537NQ5A Using a Wide Vin Controller with 60V NexFETs VIN: 24V/36V VOUT: 5V IOUT: 5A LOUT: 10µH (14mΩ) Freq: 100kHz • >92% Peak Efficiency with 36VIN/5VOUT • >93% Peak Efficiency with 24VIN/5VOUT
  39. 39. Challenge #2: Low Noise Power for Sensitive Signals • VCOs, RF circuits, and data converters require low noise power supplies to reach their stated performance System Need: Application Challenges: • DC/DC converters generate ripple that can degrade the signal and/or reduce transmit/receive speed • Linear regulators dissipate heat 0 10 20 30 40 50 60 70 80 10 100 1,000 10,000 100,000 1,000,000 10,000,000 PSRR[dB] Frequency [Hz] DAC9881 PSRR vs 5V (analog supply) Input Spectrum 0.00 0.01 0.10 1.00 10.00 100.00 1000.00 10 100 1K 10K 100K 1M 10M Freq (Hz) uV/sqrt(Hz) If we used a DC/DC converter as the power supply, the ripple at higher frequencies could degrade system performance as they would not be properly filtered by the DAC alone. For example, the PSRR on the DAC9881 is low at higher frequencies. That means that it has a limited ability to filter out any high frequency input ripple and prevent it from affecting bits.
  40. 40. Know What to Look For in a Linear Regulator  PSRR (in dB) denotes the LDO’s ability to reject noise from the input power supply. The higher the absolute value, the better the LDO can attenuate ripple from the input source, prohibiting it from affecting the output rail.  Output noise voltage (µVRMS) represents the noise generated from the LDO itself. The lower this value, the less impact the LDO will have on the integrity of the desired output rail. Creating a low noise supply from >30V input Filtering out power supply noise (ripple) Preventing any noise from disrupting the signal Best Used When… • Low current needed • Don’t like switchers • Need small size/cost • High current needed • Need high efficiency • Need low ripple • Low to medium current • Radio signals involved Key Specs to review Output noise should not be too high • Need high PSRR (at the switching frequency) • Look for lowest output noise • Also want high PSRR over a wide bandwidth Don’t forget Every volt dropped through the regulator means efficiency loss Try to minimize dropout to keep heat down
  41. 41. VIN EN NR/SS VOUT FB GND COUT TPS7A30 ON OFF CIN VIN EN NR/SS VOUT FB GND TPS7A49 ON OFF CIN VIN EN NR/SS PH VSense GND TPS54060ON OFF COUTVIN - 18V – 30V +18V -18V +12V -12V -18V Switcher @300kHz +18V Switcher @ 300kHz -12V LDO +12V LDO By virtue of high PSRR and low output noise density, TPS7A49 & TPS730 are able to filter out switching noise and provide clean positive and negative rails Filtering Switching Power Supply Noise (Ripple) • For high current needs, the power dissipation of a linear regulator may be too high • Combining a switching converter with a high PSRR linear regulator can achieve an excellent balance of high efficiency and low noise
  42. 42. TPS7A40 LM2936HV TPS7A16 TPS709 TPS7A49 TPS7A30 TPS7A47 TPS7A33 IOUT (A) 0.05 0.05 0.1 0.15 0.15 0.2 1 1 VIN (V) 7-100 5.5-60 3-60 2.7-30 3-36 -3 to -36 3-36 -3 to -36 VOUT (V) 1.1-90 3-5 1.2-18.5 1.2-5 1.2-33 -1.18 to -33 1.4-34 -1.2 to -33 Output Noise 58uVrms 500uVrms - 190uVrms 12.7uVrms 14uVrms 4uVrms 16uVrms PSRR @ 100kHz 65dB @ 100Hz 60dB @ 120Hz 50dB @ 100Hz 52dB @ 1kHz 53dB 55dB 60dB 64dB VOUT Accuracy (%) 2.5 +/-2 2 2 1.5 1 1 Dropout (mV) 780 @ 50mA 200 265mV @ 100mA 245 @ 50mA 260mV @ 100mA 215 @ 100mA 307 @ 1A 307 @ 1A Package (bold: smallest) 8MSOP- PowerPAD SOT-223, 8SOIC, 8VSSOP, TO-252 8MSOP- PowerPAD 6-SON SOT-223 SOT-23 8MSOP- PowerPAD 8MSOP- PowerPAD 20-SON 20-SON 7-TO-220 Solution Size 3x5mm + 3 caps + 2 resistors 5mm x 3mm + 2 caps 3x5mm + 3 caps + 1 resistor 2x2mm + 2 caps 3x5mm + 4 caps + 2 resistors 3x5mm + 4 caps + 2 resistors 5x5mm + 3 caps 5x5mm + 3 caps Wide Vin Linear Regulator Selection Guide Look for Wide Vin parts when the input can experience transients Pick parts with high PSRR when you need to filter out switching noise Look for parts with low output noise when dealing with very sensitive RF signals that require a low noise floor
  43. 43. Tools to Help You Start Your Next Wide Vin Circuit Design Learn with Wide Vin Videos Start a design today with WEBENCH® Designer Get design tips from TI experts on E2E Power Forum Jump start your system design with TI Designs Order TI eval modules optimized for your systems LM27403 Tiny 30A POL Module LM5017 Multi-output Fly-buck EVM
  44. 44. For More Information www.ti.com/WideVin
  45. 45. Thank You
  46. 46. Questions? Mary Gannon Design World mgannon@wtwhmedia.com Phone: 440.234.4531 Twitter: @DW_MaryGannon Jim MacDonald Texas Instruments James.macdonald@ti.com Phone: 669-721-7458
  47. 47. Thank You  This webinar will be available at designworldonline.com & email  Tweet with hashtag #DWwebinar  Connect with Design World  Discuss this on EngineeringExchange.com

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