DC/DC conversion CookbookA simple step by step guide to select the most appropriate voltage regulator for your application Piercarlo Scimonelli Presentation outline • What you need to know, to discuss intelligently • Checklist and Selection Procedure • Examples / ST products 2 Voltage Regulators A Voltage Regulator keeps a constant Output Voltage with varying: • Output current load regulation • Input voltage line regulation Input Voltage (Vin) Voltage Regulator Output Voltage (Vout) Output Current (Iout) The three most important parameters: Vin, Vout, Iout 3 Ideal Voltage Regulator V-I Characteristic Vout Iout 4 5 .Voltage Regulator simplified block diagram Voltage regulators operate by comparing the output voltage to an internal fixed reference. The difference is amplified and used to control the output voltage. This is what we call a closed-loop feedback. Classification of power switching topologies Source: APPLICATION BRIEF 0014 (N.Siciliano) 6 . Step down Converter (Buck) IL SW1 ISW1 TON Io SW2 ISW2 IL VO V IN D T ON T Io Vsw Vo TON T . Closing the loop – Voltage Mode sawtooth VC D·Ts Ts Closed Loop Feedback (Voltage Mode) L597x L598x L798x . Closing the loop – Current Mode L RSEN Slope comp R Ki Vin PWM Error OpAmp output (Vc) Vo Inductor Co current signal iL signal Slope R2 Compensation VFB Network R1 Comparator vc D·Ts Ts Error Vref Op-Amp Closed Loop Feedback (Current Mode) ST1Sx L692x . Power dissipation in Voltage Regulators 1) Power dissipated when the switches are closed (conduction losses): PON = IOUT2 x (RDSONHS x D + RDSONLS x (1-D) + RL) 2) Power dissipated during the commutations (switching losses): PSW = VIN x IOUT x FSW x (TON + TOFF)/2 3) Power dissipated when the device is not switching: PQ = VIN x IQ Power dissipated in a linear regulator: PD = (VIN-VOUT) x IOUT + VIN x IQ . 8V to 3.6V.Example: low Iq regulators in powering STM32 Current consumption: • Depends on operating mode • Decreases at lower VDD • Inreases with temperature • Increases with clock speed STM32L Vcc: 1. Icc: 1uA to 100mA Supply current in standby is the same order of magnitude as the quiescent current of voltage regulators . 8V to 3.STLQ015 150mA. Ultra Low Quiescent Current LDO regulator Input Voltage from 1.3V Excellent load transient response Stable with low ESR.5V to 5.2x1.5V Ultra Low Quiescent Current: Fixed VOUT: 0. SMD ceramic caps 1.0 μA (typ) at no load 1 nA (typ) in OFF mode SOT666-6L (1.6mm) . ST1S15 .Switching Frequency Impact Performance • • • • • Efficiency Thermal Output Voltage Ripple Dynamic Performance Board space availability (needs low frequency) (needs low frequency) (needs high frequency) (need high frequency) (needs high frequency) Typical cases: ~100kHz To maximize efficiency (Energy harvesting) SPV1040 250-500KHz High voltage buck regulators (Industrial/Autom otive) L7985. STBB1. STLA02 3MHz up to 6MHz Extreme board space constraints (Portable Fitness. Smart phones/tablets) STBB2. L6738 1MHz-3MHz Portable applications / size constraints (Trade off between board space and efficiency) ST1S31/32. L7986. PM668x 600KHz-1MHz Cost/performance trade-off (Consumer/Compu ter) ST1S40. Advantage: Low noise and better EMI control due to constant switching frequency (easy to filter out). PWM switching control PWM (pulse-width modulation) . Higher output voltage ripple .PFM vs. Disadvantages: Variable sw frequency (Noise and EMI). Disadvantage: Lower power efficiency at light load (because of swithing losses) PFM (pulse-frequency modulation) PFM Advantages: High power efficiency over a wide range of load. 4MHz synchronizable up to 2 MHz (L6928) Current Mode Control L6925 Thermal shut down (150C) 15 . synchronizable up to 1.4 MHz (L6925/6) Freq.6V VIN (100% DC) L6926/L6928: PGOOD & RUN 1% output voltage accuracy IOUT up to 800mA 25uA quiescent current Selectable Low noise or low consumption mode (PWM/PFM) Freq.5V for L6925) L6925: LBI & LBO.: 600KHz.High efficiency at light load: L6925/6/8 Step-down switching regulators • • • • • • • • • • Differentiating functions: VIN : 2V 5.5V (2.: 1.7V 5.7V VOUT: adjustable 0. UVLO @ 2. 5V Iout 30mA Cin/Cout 10uF Rc 20Kohm Cc 330pF 16 .L6928 low noise or low power (burst) mode Burst mode High efficiency Low noise Forced PWM Vin 4.2V Vout 1. very high efficiency HS1 LS1 Multi-Output Controller or Converter Compactness HS2 LS2 HS1 LS1 HS2 LS2 Multiphase controller Load higher than 30A High efficiency. low ripple. compact LS1 HS1 LS1 Single Output Switching Controller: external mosfets. up to 5A load. small i/o filters . up to 30A load. fast transient response.Switching regulator selection based on output current HS1 Switching Converter: internal mosfet(s). low efficiency . up to 7A Low noise.Switching Regulator vs. Linear Voltage Regulator Linear Regulator: No inductor MOSFET or Bipolar pass element <500mA typ. LM317) Vdrop >2V Vin .2V Minimum Power dissipation Vin Vin .Vout Vout Very Low-Drop (LFxx/LD29xxx) Vdrop 0.7V Vin Vin .2V-0.Vout Vout Vin Semi Low-Drop (LD1117/LD108x) Vdrop 0.5V Vin .LDO: Low Drop-Out (voltage regulator) The drop-out voltage is the minimum voltage across the regulator to maintain regulation Vout Standard Linear Regulators (L78xx.8V-1.Vout Vout Ultra LDO (LD39xxx) Vdrop <0.Vout Vout Vin Vin . 5A/div COUT=47uF L=6.5A/us .8uH FSW=500kHz Timescale 100us/div VIN=12V.Load Transient Response VOUT AC coupled 100mV/div IL 0. VOUT=3. SRILOAD=2.3V. IOUT= from 1µA to 10mA Static Load Regulation Vout Load Transient response Tradeoff between: BW of Error Amplifier vs. COUT=10µF. Power consumption Iout { { .STLQ015 Load Transient Load Transient Response VIN=5.5V CIN=1µF. Soft-Start L598x SRVREF • Staircase ramp on internal VREF • 64 steps. 9mV each step • 32 clock cycles each step 0.6 FSW 2048 SRVOUT SRVREF 1 R1 R2 . Synchronous rectification vs. non-synchronous 12V Vin 3.3V Vout 3A Iout ST1S10 L7981 23 . converter always more efficient than a non-synchr? ST1S10 24 .Synchronous rectification vs. non-synchronous L7981 Is a synchr. Current Mode) … The best device is that which fits the application . efficiency at light load Feedback loop (Voltage Mode vs.summary • • • • • • • • • • Input Voltage (VIN) Output Voltage (VOUT) Output DC current (IOUT) Power Conversion Efficiency: a measure of power losses smaller package and longer battery life Switching frequency: ON/OFF time of power switch Impacts size of external components and efficiency Quiescent Current (Iq): required to power internal circuitry Impact on light load efficiency Package Thermal Resistance Rth: ability to dissipate heat impact on board space and robust thermal design Switching control (PWM – PFM): noise vs.Application requirements in a DC/DC conversion . FETs). choose between controller (ext. power good. light load efficiency. quiescent current. switching frequency. step down.DC/DC Selection Procedure Summary • From Vin and Vout. buck-boost) • Based on the output current and efficiency. select the topology (step-up. synchronization. board space. output ripple etc… etc… • Always ask what is “key” to the application 26 . transient response. soft start. converter (int. FETs) or Linear • Select the device starting from the input voltage spec and max DC current (if integrated FETs) to meet the application requirements of input voltage range and load • Consider any other design constraint: operating temperature range. FETs) Switching Converters (int.DC-DC Conversion Portfolio 27 Linear Voltage Regulators Low Drop Out (LDOs) Battery & Power Management PMICs Shunt Voltage Ref. FET) Single and Multi output & LED drivers Single and Multi phase Power over Ethernet (PoE) ASICs . ASSP Switching Controllers (ext. L5988/89 Continuous output current from 350mA to 4A Wide range of max input voltage: 5V TO 60V SOT23. high Vin PMxx. L798x. 3-5A synchr. L692x. A798x Battery powered applications High performance. L692x A597x. ST1S40. ST1Sxx. L598x Consumer Value Line 12V Vin. high Vin ST1S14. Q/DFN3x3 and 4x4mm. 3-4A.Switching Converter segmentation 28 Non synchronous. ST1S31/2. high at light load Automotive Grade. and TSSOP . L597x. ST1S41 Synchronous. HSO8. ST1S1x PM8903. synchr. PM6644. Step Down Converters – First buying choice 60 L4976 L4973 L4978 L4971 Synchronuos ST1S14 MAXIMUM OPERATING INPUT VOLTAGE 50 NON-Synchronous L7986 L7985 40 L5970 L5972/3A L5974/5A L5973/4A Synchr. high at light load L5975 PGood L6902 30 L7980 PM6644 L5980 20 L5981 L5983 L5985/45 L5986 L7981 L5987/47 ST1S10 ST1S41 L5988/89 ST1S40 ST1S03 10 0 ST2S06 ST1S15 0 ST2S08 ST1S12 ST1S03A L6925/6/8 1 PM8903 ST1S09 ST1S06 2 ST1S32 ST1S31 ST1S30 3 MAXIMUM OUTPUT CURRENT 4 5 6 . 5V up to 38V) 200ns minimum Ton Internal Soft-start QFN10 3x3 Enable pin Embedded protection features Suitable for MLCC output filter Typ RDSon=150mΩ QFN 3x3 10L .Rth j-amb 60 C/W HSO8 .L7985-L7986 2-3A output current in QFN3x3-10L and HSOP8 packages P-channel power MOS: 100% DC operation and no bootstrap capacitor High switching frequency (250KHz. adjustable up to 1MHz) with Synchronization capability (180° out of phase) Wide input voltage range (4.Rth j-amb 40° C/W HSOP8 L7986/A L7985/A 3A / up to 1MHz 2A / up to 1MHz . ST1S40/41 Switching Frequency: 800kHz Continuous output Current Capability: 3/4A 4/5A peak current limit Output Voltage: Adjustable from 0.8V Operating Input voltage 4V to 18V Ceramic Capacitors and small Inductor Soft-Start integrated circuit Integrated 69mOhm Low side RDSon Integrated 95mOhm High side RDSon Efficiency: up to 95% Enable pin or Power Good SO8. HSOP8 and MLP4x4 packages Pin-to-pin with ST1S10 SO-8 ST1S41 DFN – 8L 4x4mm ST1S40 4A / 850kHz 3A / 800kHz HSOP-8 Package Output Current Commercial Code SO8 3A ST1S40IDR SO8-BW 3A ST1S40IPHR DFN4x4 – 8L 3A ST1S40IPUR DFN4x4 – 8L 4A ST1S41PUR HSOP8 4A ST1S41PHR . switching frequency in PWM mode Pulse skipping mode at light load Latched OVP and UVP High accuracy (±0.3V voltage reference 4.465V or adjustable 0.PM6644 350mA step down and 3.5V to 25V input voltage range (35V AMR) Vout: fixed 3.9V to 8V 350mA valley current limit Constant On-Time Control Progr.6%) 3.3V reference 32 . APM – Jun 2011 600 .LDO Positioning (≤500mA) Semi-low drop 0.7V ST715 Ultra-low drop VDROP<0.8V<VDROP<1.2V<VDROP<0.2V MAXIMUM OPERATING INPUT VOLTAGE 25 L4931 KFxx 20 LD2980 LD2979 LD2985 LD2981 AG LFxx 15 LDFMxx LK112 10 STLQ50 LD3985 5 0 0 100 LK112S LD39115 LD39015 LD59015 LDCL015 LDLN015 STLQ015 LDK115 LDK120 200 LDS3985 LD39030 LD39130 LD39050 LD3980 300 400 500 MINIMUM GUARANTEED OUTPUT CURRENT P.7V 30 Very-low drop 0. Scimonelli . 8V<VDROP<1. Scimonelli .APM – Jun 2011 3500 .LDO Positioning (≥500mA) 35 L4940 LD1086 L4941 LD1085 MAXIMUM OPERATING INPUT VOLTAGE 30 Semi-low drop 0.7V 25 Very-low drop 0.7V KFxx 20 Ultra-low drop VDROP<0.2V<VDROP<0.2V LDFMxx LD1117A LD1117 LFxx AG 15 LDFMxx LD29080 10 LD39080 ST1L02 ST1L04 LD29150 LD29300 LD39150 LD39300 5 LD39100 LD39050 ST1L05 LD49150 LD49300 0 0 500 1000 1500 2000 2500 3000 MINIMUM GUARANTEED OUTPUT CURRENT P. 8mm2 • LD59015: 150mA.CSP4 bumps 1x1mm2 • LD39115J: 150mA . Soft-Start .3 35 . DFN2x2 • LD39130: 300mA .CSP4 bumps 0.8mm2 • LD39030SJ : 300mA.69x0. SC70 • LDCL015: 150mA – Capless.69mm2 and DFN 1.8x0.CSP4 bumps 0.8x0.LDOs in portable applications • LD39015J: 150mA . Very High PSRR.CSP4 bumps 0. SOT23 • LDLN015: 150mA – Very Low Noise.2x1. high efficiency buck PM6644 .500mA.7uA Iq. 6MHz.1. LDO STLQ50 3 μA Iq. 150 mA Iout. 150mA Iout. on/off L6924D Lithium battery charger STW4102 – Lithium Battery charger L6920D 1 A step-up. LDO LD39015/LD39115 Low noise. low Iq.3V Vref SPV1040 boost with MPPT for solar battery chargers LMV4041.6 Vin L6928 Sync step-down.2V Vref with 0. 95 % 2-5.DC/DC conversion for 5V Vin or lower Voltage Regulation & Battery Chargers STBB1 Buck boost STLQ015 1.350mA. 50 mA Iout. down to 0.5 Vin ST1S15 . high efficiency buck + 3.1% accuracy in SC70 Display drivers STLA02 (6 LED backlight driver) STLED25 (2x5 LED backlight driver) STP2/4CMP (2/4 ch charge pump) STODxx (AMOLED) . 0.DC/DC conversion for 12V Vin CONVERTERS (Int. 0. SYNC. PGOOD DFN10 SO16N HTSSOP16 QFN24 4x4 HTSSOP20 QFN16 3x3 L6725. L6727 Up to 19V VINPUT. PGOOD.8V min VOUT 300/600KHz EN.No sink cap. 0. SS.No Sink).6V min VOUT Up to 1MHz OVP(Latch .FETs) • Consumer • Computer • Anything powered off your friendly wall wart CONTROLLERS (Ext. SS. SS (Sink .FETs) Part Number VINPUT/VOUT range FSW features Package L6726A. IHN. UVP. Adj UVLO.2V (15V ABS) VINPUT.8V min VOUT Adj. UVP SO8 L6728 Up to 13. L6730 L6731. OCP. differential CS & “GREEN low power mode” . SS. PGOOD (with adj. OVP. OCP. EN. Sink. OVP. L6738 Up to 19V VINPUT.5V to 14V VINPUT. OCP. Ext or Internal REF.No Latch). OVP.8V min VOUT 270/300khZ EN. delay) .. OCP (CC or HICCUP). L6732 4. 0. FETs) • Industrial Applications • Printers • Automotive/Marine battery Powered applications . 100mA Up to 28V QFN 5x5 PM6685 2+2 3.3V 5V - (1)3.3V + (2)5V 100mA up to 28V QFN 5x5 CONVERTERS (Int. - - VINLDO/2 2A Up to 28V /36V QFN 4x4 PM6675/A 1+1 Adj. - Adj. - - Adj.FETs) PN VOUT # (SW +LDO) VOUTSW 1 VOUTSW 2 VOUTS W 3 VOUTLDO(S) ILDO VIN range package PM6670/A 1+1 Adj. 2A Up to 28V/36V QFN 4x4 PM6680/A 2+1 Adj. - 5V 200mA Up to 28V/36V QFN 5x5 PM6681/86 2+1 Adj. Adj. Adj.DC/DC conversion for 24V to 55V Vin CONTROLLERS (Ext. Tools and resources . output voltage and current Interactive schematics and BOM: change the parameters of external components Evaluate the performance of your design: stability.… Connect to Cadence® Orcad Pspice 40 . efficiency.com/edesignstudio Complete designs in a few steps starting from input voltage.st.eDesign Suite www. thermal. Create a new project and choose an application type Input your specifications Login to www..com/edesignstudio (after online registration) The design is ready .A complete design in a few steps….st. Helps select the optimal IC for your needs You can filter the IC selecting specific features . displays bode plots. power losses and efficiency .Evaluate the performance of your design Waveforms simulator Bode plots Loss distribution Efficiency Simulates key voltage and current waveforms. Your design gets portable and exportable Export the current design project for Pspice Simulation in OrCAD Save your project to ST server/eDesign Studio My Projects folder It can accessed from ANY computer through your eDesign Studio account . Print a summary of your project . com Presentation Title 46 25/04/2012 .st.Parametric Search on www. 47 . 48 .