LTM8078 Dual 1.4A, Single 2.8A Step-Down Silent Switcher Module Regulator FEATURES DESCRIPTION Two Complete Step-Down Switching Power Supplies n Low Noise Silent Switcher(R) Architecture n CISPR22 Class B Compliant n CISPR25 Class 5 Compliant n Wide Input Voltage Range: 3V to 40V n Wide Output Voltage Range: 0.8V to 10V n 1.4A Continuous Output Current per Channel at 24VIN, 3.3VOUT, TA = 85C n Multiphase Parallel Operation to Increase Current n Selectable Switching Frequency: 300kHz to 3MHz n Compact Package (6.25mm x 6.25mm x 2.22mm) Surface Mount BGA The LTM(R)8078 is 40VIN, dual 1.4A/single 2.8A step-down Silent Switcher Module(R) regulator. The Silent Switcher architecture minimizes EMI while delivering high efficiency at frequencies up to 3MHz. Included in the package are the controllers, power switches, inductors, and support components. Operating over a wide input voltage range, the LTM8078 supports output voltages from 0.8V to 10V, and a switching frequency range of 300kHz to 3MHz, each set by a single resistor. Only the bulk input and output filter capacitors are needed to finish the design. The LTM8078 product video is available on website. n APPLICATIONS Automated Test Equipment Distributed Supply Regulation n Industrial Supplies n Medical Equipment n n The LTM8078 is packaged in a compact (6.25mm x 6.25mm x 2.22mm) over-molded Ball Grid Array (BGA) package suitable for automated assembly by standard surface mount equipment. The LTM8078 is available with SnPb (BGA) or RoHS compliant. All registered trademarks and trademarks are the property of their respective owners. Click to view associated Video Design Idea. TYPICAL APPLICATION 3.3VOUT and 5VOUT from 7V to 40V Dual Step-Down Converter 95 VIN1 RUN 1F 17.8k LTM8078 FB1 RT (1.6MHz) 78.7k 100F VOUT1 3.3V 1.4A 90 GND 85 80 OM VOUT2 OMC BIAS VIN2 1F VOUT1 EFFICIENCY (%) VIN 7V TO 40V Efficiency,V IN VIN= =24V, 24V, BIAS = 5V Efficiency, BIAS = 5V FB2 VOUT2 5V 1.4A 47.5k 47 F 75 TA = 25C 3.3VOUT 5.0VOUT 0 0.5 1 1.5 LOAD CURRENT (A) 2 2.5 8078 TA01b 8078 TA01a PINS NOT USED: TRSS1, TRSS2, PG1, PG2, CLKOUT, SYNC Rev. A Document Feedback For more information www.analog.com 1 LTM8078 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) VINn, RUN, PGn .........................................................42V VOUTn, BIAS ..............................................................10V FBn, OM, OMC, TRSSn, RT .........................................4V SYNC...........................................................................6V Maximum Internal Temperature (Note 2)............... 125C Storage Temperature ............................. -55C to 125C Peak Solder Reflow Package Body Temperature ... 260C GND RT FB2 FB1 OM OMC BIAS 7 TRSS2 TRSS1 BANK 2 VOUT2 6 RUN 5 4 3 VIN2 BANK 3 VIN1 GND PG2 2 PG1 1 A B BANK 1 VOUT1 SYNC CLKOUT C D E F G BGA PACKAGE 49-PIN (6.25mm x 6.25mm x 2.22mm) TJMAX = 125C, JA = 31.3C/W, JCtop = 30.5C/W, JCbot = 10.6C/W, WEIGHT = 0.23g VALUES DETERMINED PER JESD 51-9, 51-12 ORDER INFORMATION PART MARKING PART NUMBER LTM8078EY#PBF LTM8078IY#PBF LTM8078IY PAD OR BALL FINISH SAC305 (RoHS) SnPb (63/37) DEVICE 8078 FINISH CODE PACKAGE TYPE MSL RATING BGA 3 1 TEMPERATURE RANGE (SEE NOTE 2) -40C to 125C 0 * Device temperature grade is indicated by a label on the shipping container. * This product is not recommended for second side reflow. This product is moisture sensitive. For more information, go to * Pad or ball finish code is per IPC/JEDEC J-STD-609. Recommended BGA PCB Assembly and Manufacturing Procedures. * BGA Package and Tray Drawings 2 Rev. A For more information www.analog.com LTM8078 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the specified operating internal temperature range, otherwise specifications are at TA = 25C. VIN1 = VIN2 = 12V, RUN = 2V unless otherwise noted (Note 2). PARAMETER Minimum VIN1 Input Voltage Minimum VIN2 Input Voltage Output DC Voltage CONDITIONS MIN TYP VIN1 = 3V MAX UNITS 3.0 2.0 l l V V 0.8 10 FBn Open FBn = 21.5k V V Maximum Output DC Current (Note 3) Quiescent Current into VINn RUN = 0V BIAS = 5V, SYNC = 0V, No Load BIAS = 5V, SYNC = 3.3V, No Load 2 60 10 2.5 Current into BIAS RUN = 0V, BIAS = 5V BIAS = 5V, SYNC = 3.3V, No Load 7 Line Regulation 5V < VINn <40V, IOUTn = 0.5A 0.1 Load Regulation 12VINn, 0.1A < IOUTn < 2A 0.2 % Output RMS Ripple 3.3VOUTn 10 mV FBn Voltage l Current out of FBn 792 784 VOUTn = 1V, FBn = 0V 800 A A mA 1 A mA % 808 816 4 Minimum BIAS for Proper Operation Switching Frequency A 4 mV mV A 3.2 RT = 113k RT = 30.9k RT = 7.15k RUN Threshold RUN Input Current RUN = 0V PGn Threshold at FBn FBn Rising FBn Falling PGn Output Sink Current PGn = 0.1V kHz MHz MHz 0.74 V 1 740 860 CLKOUT VOH SYNC Input High Threshold A mV mV 100 CLKOUT VOL V 300 1 3 A 0 V 3.3 V 1.5 V SYNC Input Low Threshold SYNC Threshold to Enable Spread Spectrum 2.8 SYNC Current SYNC = 6V TRSSn Source Current TRSSn = 0V TRSSn Pull-Down Resistance Fault Condition, TRSSn = 0.1V Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The LTM8078E is guaranteed to meet performance specifications from 0C to 125C internal. Specifications over the full -40C to 125C internal operating temperature range are assured by design, characterization and correlation with statistical process controls. 0.8 V 4 V 65 A 2 A 170 The LTM8078I is guaranteed to meet specifications over the full -40C to 125C internal operating temperature range. Note that the maximum internal temperature is determined by specific operating conditions in conjunction with board layout, the rated package thermal resistance and other environmental factors. Note 3: The maximum current out of either channel may be limited by the internal temperature of the LTM8078. See output current derating curves for different VIN, VOUT and TA. Rev. A For more information www.analog.com 3 LTM8078 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25C, operating per Table1,unless otherwise noted. Efficiency, VOUT = 1.0V BIAS = 5V 90 75 75 80 65 45 EFFICIENCY (%) 85 55 65 0 0.5 1 1.5 LOAD CURRENT (A) 2 45 2.5 12VIN 24VIN 36VIN 0 0.5 1 1.5 LOAD CURRENT (A) 2 80 80 EFFICIENCY (%) 80 EFFICIENCY (%) 90 70 60 12VIN 24VIN 36VIN 0 0.5 1 1.5 LOAD CURRENT (A) 2 50 2.5 0 0.5 1 1.5 LOAD CURRENT (A) 2 50 2.5 95 85 85 85 EFFICIENCY (%) 95 EFFICIENCY (%) 95 55 75 65 0 0.5 1 1.5 LOAD CURRENT (A) 2 2.5 8078 G07 12VIN 24VIN 36VIN 0 0.5 55 1 1.5 LOAD CURRENT (A) 2 2.5 8078 G06 Efficiency, VOUT = 3.3V BIAS = 5V 12VIN 24VIN 36VIN 2.5 70 8078 G05 Efficiency, VOUT = 2.5V BIAS = 5V 65 2 60 12VIN 24VIN 36VIN 8078 G04 75 1 1.5 LOAD CURRENT (A) Efficiency, VOUT = 2.0V 90 50 0.5 BIAS == 5V 5V BIAS 90 70 0 8078 G03 Efficiency, VOUT = 1.8V BIAS BIAS == 5V 5V 60 EFFICIENCY (%) 50 2.5 12VIN 24VIN 36VIN 8078 G02 Efficiency, VOUT = 1.5V BIAS BIAS == 5V 5V 4 70 60 55 12VIN 24VIN 36VIN 8078 G01 EFFICIENCY (%) Efficiency, VOUT = 1.2V BIAS = 5V 85 EFFICIENCY (%) EFFICIENCY (%) Efficiency, VOUT = 0.8V BIAS = 5V Efficiency, VOUT = 3.3V BIAS = 5V, FSW SW = 2MHz 75 65 12VIN 24VIN 36VIN 0 0.5 1 1.5 LOAD CURRENT (A) 2 2.5 8078 G08 55 12VIN 24VIN 36VIN 0 0.5 1 1.5 LOAD CURRENT (A) 2 2.5 8078 G09 Rev. A For more information www.analog.com LTM8078 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25C, operating per Table1,unless otherwise noted. 95 85 85 75 Efficiency, VOUT = 8V BIAS = 5V 100 90 75 65 65 55 Efficiency, VOUT = 5V BIAS = 5V, FSW SW = 2MHz EFFICIENCY (%) 95 EFFICIENCY (%) EFFICIENCY (%) Efficiency, VOUT = 5V BIAS = 5V 12VIN 24VIN 36VIN 0 0.5 1 1.5 LOAD CURRENT (A) 2 55 2.5 70 12VIN 24VIN 36VIN 0 0.5 1 1.5 LOAD CURRENT (A) 2 Efficiency, VOUT = 10V 1.5 2.0 12VIN 24VIN 36VIN 1.0 12VIN 24VIN 36VIN 0.5 1 1.5 LOAD CURRENT (A) 2 0 2.5 0 0.5 1 1.5 LOAD CURRENT (A) 2 Power Loss, VOUT = 1.2V 0.5 2.0 0.5 1 1.5 LOAD CURRENT (A) 2 2.5 8078 G16 1 1.5 LOAD CURRENT (A) 2 1.0 0 2.5 12VIN 24VIN 36VIN 1.5 1.0 0.5 0.5 0 0.5 Power Loss, VOUT = 1.8V BIAS = 5V, Burst Mode Operation POWER LOSS (W) 1.0 0 8078 G15 12VIN 24VIN 36VIN 1.5 POWER LOSS (W) POWER LOSS (W) 2.0 12VIN 24VIN 36VIN 1.5 0 2.5 Power Loss, VOUT = 1.5V BIAS = 5V, Burst Mode Mode Operation 5V, Burst 5V, Burst Burst Mode Mode Operation BIAS = 5V, 2.5 1.0 8078 G14 8078 G13 2.0 2 0.5 0.5 70 1 1.5 LOAD CURRENT (A) 12VIN 24VIN 36VIN 1.5 POWER LOSS (W) 90 POWER LOSS (W) 2.0 EFFICIENCY (%) 100 0 0.5 Power Loss, VOUT = 1V BIAS = 5V, Burst Mode Mode Operation 5V, Burst 5V, Burst Burst Mode Mode Operation BIAS = 5V, 80 0 8078 G12 Power Loss, VOUT = 0.8V BIAS = 5V 0 60 2.5 12VIN 24VIN 36VIN 8078 G11 8078 G10 60 80 0 0.5 1 1.5 LOAD CURRENT (A) 2 2.5 8078 G17 0 0 0.5 1 1.5 LOAD CURRENT (A) 2 2.5 8078 G18 Rev. A For more information www.analog.com 5 LTM8078 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25C, operating per Table1,unless otherwise noted. Power Loss, VOUT = 2V 1.0 0 0.5 1 1.5 LOAD CURRENT (A) 2 1.0 0 2.5 0 0.5 1 1.5 LOAD CURRENT (A) 2 0.5 0 0.5 1 1.5 LOAD CURRENT (A) 2 2.5 POWER LOSS (W) 1.5 1.0 0 2.5 0.5 0 0.5 1 1.5 LOAD CURRENT (A) 2 1.0 0.5 0 0.3 2.0 1.5 1.0 0.5 1 1.5 LOAD CURRENT (A) 2 2.5 Input vs Load Current VOUT OUT = 0.8V 12VIN 24VIN 36VIN 0.2 0.1 0.5 0 0.5 1 1.5 LOAD CURRENT (A) 2 2.5 0 0 0.5 1 1.5 LOAD CURRENT (A) 2 8078 G25 6 0 8078 G24 INPUT CURRENT (A) 1.5 0 2.5 12VIN 24VIN 36VIN 2.5 POWER LOSS (W) POWER LOSS (W) 3.0 2.0 2.5 1.0 Power Loss, VOUT = 10V BIAS = 5V, Burst Mode Operation 12VIN 24VIN 36VIN 2 1.5 8078 G23 Power Loss, VOUT = 8V BIAS = 5V, Burst Mode Operation 2.5 1 1.5 LOAD CURRENT (A) 12VIN 24VIN 36VIN 2.0 8078 G22 3.0 0.5 Power Loss, VOUT = 5V, 2MHz BIAS = 5V, Burst Mode Operation 0.5 0 0 8078 G21 12VIN 24VIN 36VIN 2.0 POWER LOSS (W) POWER LOSS (W) 2.5 1.0 0 2.5 Power Loss, VOUT = 5V BIAS = 5V, Burst Mode Operation 12VIN 24VIN 36VIN 1.5 1.0 8078 G20 Power Loss, VOUT = 3.3V, 2MHz BIAS = 5V, Burst Mode Operation 2.0 1.5 0.5 8078 G19 2.5 12VIN 24VIN 36VIN 2.0 0.5 0.5 0 2.5 12VIN 24VIN 36VIN 1.5 POWER LOSS (W) 1.5 POWER LOSS (W) 2.0 12VIN 24VIN 36VIN POWER LOSS (W) 2.0 Power Loss, VOUT = 3.3V BIAS = 5V, Burst Mode Operation Power Loss, VOUT = 2.5V BIAS = 5V, Burst Mode Mode Operation 5V, Burst BIAS = 5V, 5V, Burst Burst Mode Mode Operation 2.5 8078 G26 0 0 0.5 1 1.5 LOAD CURRENT (A) 2 2.5 8078 G27 Rev. A For more information www.analog.com LTM8078 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25C, operating per Table1,unless otherwise noted. Input vs Load Current 0.4 0.3 0.2 0.1 0 0 0.5 1 1.5 LOAD CURRENT (A) 2 0.2 0.1 0 0.5 8078 G28 0.6 12VIN 24VIN 36VIN 0.2 0 0 0.5 1 1.5 LOAD CURRENT (A) 2 2 0.8 12VIN 24VIN 36VIN 0.4 0.2 0 2.5 0 0.5 1 1.5 LOAD CURRENT (A) 2 0 0 0.5 1 1.5 LOAD CURRENT (A) 2 2.5 8078 G34 0.5 1 1.5 LOAD CURRENT (A) 2 Input vs Load Current VOUT = 2.5V 12VIN 24VIN 36VIN 0.4 0.2 0 0.5 1 1.5 LOAD CURRENT (A) 2 Input vs Load Current 2.0 12VIN 24VIN 36VIN 0.6 0.3 0 0.5 1 1.5 LOAD CURRENT (A) 2.5 8078 G33 Input vs Load Current VOUT = 5V 0.9 0 2.5 0.6 0 2.5 INPUT CURRENT (A) 0.75 INPUT CURRENT (A) INPUT CURRENT (A) 1.2 12VIN 24VIN 36VIN 0.25 0 8078 G32 Input vs Load Current VOUT = 3.3V 0.50 0.2 8078 G30 Input vs Load Current VOUT = 2V 2.0V 8078 G31 1.00 12VIN 24VIN 36VIN 0.4 0 2.5 INPUT CURRENT (A) Input vs Load Current VOUT = 1.8V 0.4 1 1.5 LOAD CURRENT (A) Input vs Load Current VOUT = 1.5V 8078 G29 INPUT CURRENT (A) INPUT CURRENT (A) 0.6 0.6 12VIN 24VIN 36VIN 0.3 0 2.5 Input vs Load Current VOUT OUT = 1.2V INPUT CURRENT (A) 12VIN 24VIN 36VIN INPUT CURRENT (A) INPUT CURRENT (A) 0.4 1V VOUT = 1.0V 2 2.5 8078 G35 VOUT = 8V 12VIN 24VIN 36VIN 1.5 1.0 0.5 0 0 0.5 1 1.5 LOAD CURRENT (A) 2 2.5 8078 G36 Rev. A For more information www.analog.com 7 LTM8078 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25C, operating per Table1,unless otherwise noted. 2000 0.6 0 0 0.5 1 1.5 LOAD CURRENT (A) 2 1500 1000 500 0 2.5 0 10 8078 G37 BIAS Current vs Frequency VIN = 12V, VOUT = 3.3V, BIAS = 5V Forced Continuous Mode BIAS CURRENT (mA) 12 9 6 3 0 0 1 2 SWITCHING FREQUENCY (MHz) 30 3 1.5 1.0 0LFM 0.5 0 0 12VIN 24VIN 36VIN 25 50 75 100 AMBIENT TEMPERATURE (C) 1.0 0LFM 0.5 0 0 12VIN 24VIN 36VIN 25 50 75 100 AMBIENT TEMPERATURE (C) 125 0.5 1 1.5 LOAD CURRENT (A) 2 Derating, VOUT = 1.0V, BIAS = 5V, DC2777A Demo Board Both Channels at At Same Same Load Load 125 2.5 2.0 1.5 1.0 0LFM 0.5 0 0 12VIN 24VIN 36VIN 25 50 75 100 AMBIENT TEMPERATURE (C) 125 8078 G44 2.5 8078 G39 2.5 2.0 1.5 1.0 0LFM 0.5 0 0 12VIN 24VIN 36VIN 25 50 75 100 AMBIENT TEMPERATURE (C) 125 8078 G42 Derating, VOUT = 1.5V BIAS = 5V, DC2777A Demo Board At Same Same Load Load Both Channels at 8078 G43 8 0 8078 G41 MAXIMUM LOAD CURRENT PER CHANNEL (A) MAXIMUM LOAD CURRENT PER CHANNEL (A) 1.5 0 8078 G38 2.0 Derating, VOUT = 1.2V BIAS = 5V, DC2777A Demo Board At Same Same Load Load Both Channels at 2.0 400 40 2.5 8078 G40 2.5 800 Derating, VOUT = 0.8V BIAS = 5V, DC2777A Demo Board Both Channels at At Same Same Loadt Load MAXIMUM LOAD CURRENT PER CHANNEL (A) 15 20 VIN (V) Dropout Voltage vs Load Current VOUT = 5V, BIAS = 5V 1200 MAXIMUM LOAD CURRENT PER CHANNEL (A) 1.2 1600 Derating, VOUT = 1.8V, BIAS = 5V, DC2777A Demo Board At Same Load Both Channels at MAXIMUM LOAD CURRENT PER CHANNEL (A) 1.8 Input Current vs VIN VOUT Short Circuited DROPOUT VOLTAGE (mV) 12VIN 24VIN 36VIN INPUT CURRENT (mA) INPUT CURRENT (A) 2.4 Input vs Load Current VOUT = 10V 2.5 2.0 1.5 1.0 0LFM 0.5 0 12VIN 24VIN 36VIN 0 25 50 75 100 AMBIENT TEMPERATURE (C) 125 8078 G45 Rev. A For more information www.analog.com LTM8078 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25C, operating per Table1,unless otherwise noted. 1.0 0LFM 0.5 0 0 12VIN 24VIN 36VIN 25 50 75 100 AMBIENT TEMPERATURE (C) 125 1.5 1.0 0 1.5 1.0 0LFM fSW = 2MHz 12VIN 24VIN 36VIN 0 25 50 75 100 AMBIENT TEMPERATURE (C) 0 25 50 75 100 AMBIENT TEMPERATURE (C) 125 2.5 2.0 1.5 1.0 0LFM 0.5 0 12VIN 24VIN 36VIN 0 25 50 75 100 AMBIENT TEMPERATURE (C) 8078 G49 1.5 1.0 0LFM 0.5 0 12VIN 24VIN 36VIN 0 25 50 75 100 AMBIENT TEMPERATURE (C) 125 1.0 0LFM 0.5 0 12VIN 24VIN 36VIN 0 25 50 75 100 AMBIENT TEMPERATURE (C) Derating, VOUT = 5V BIAS = 5V, DC2777A Demo Board at Same Load Both Channels At 125 2.5 2.0 1.5 1.0 0LFM 0.5 0 12VIN 24VIN 36VIN 0 25 50 75 100 AMBIENT TEMPERATURE (C) 8078 G52 125 8078 G53 125 8078 G48 2.5 2.0 1.5 1.0 0 LFM fSW = 2MHz 0.5 0 12VIN 24VIN 36VIN 0 25 50 75 100 AMBIENT TEMPERATURE ( C) 125 8078 G51 Derating, VOUT = 10V BIAS = 5V, DC2777A Demo Board At Same Same Load Load x Both Channels at MAXIMUM LOAD CURRENT PER CHANNEL (A) MAXIMUM LOAD CURRENT PER CHANNEL (A) 2.0 1.5 8078 G50 Derating, VOUT = 8V BIAS = 5V, DC2777A Demo Board Both Channels At at Same Load 2.5 125 2.0 Derating, VOUT = 5V, BIAS = 5V, DC2777A Demo Board Both Channels at Same Load MAXIMUM LOAD CURRENT PER CHANNEL (A) MAXIMUM LOAD CURRENT PER CHANNEL (A) 2.0 0 12VIN 24VIN 36VIN 2.5 8078 G47 Derating, VOUT = 3.3V, BIAS = 5V, DC2777A Demo Board Both Channels at Same Load, FAt = 2MHz Both Channels Load SWSame 0.5 0LFM 0.5 8078 G46 2.5 MAXIMUM LOAD CURRENT PER CHANNEL (A) 1.5 2.0 MAXIMUM LOAD CURRENT PER CHANNEL (A) 2.0 2.5 Derating, VIN = 12V, VOUT = 1.5V BIAS = 5V, DC2777A Demo Board Both Channels at At Same Load MAXIMUM LOAD CURRENT PER CHANNEL (A) 2.5 Derating, VOUT = 3.3V, BIAS = 5V, DC2777A Demo Board Both Channels at At Same Same Load Load Derating, VOUT = 2.5V, BIAS = 5V, DC2777A Demo Board Both Both Channels Channels at At Same Same Load Load MAXIMUM LOAD CURRENT PER CHANNEL (A) MAXIMUM LOAD CURRENT PER CHANNEL (A) Derating, VOUT = 2.0V, BIAS = 5V, DC2777A Demo Board Both Channels at Same Load 2.5 2.0 1.5 1.0 0.5 0 0LFM 400LFM 0 25 50 75 100 AMBIENT TEMPERATURE (C) 125 8078 G54 Rev. A For more information www.analog.com 9 LTM8078 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25C, operating per Table1,unless otherwise noted. 2.0 1.5 1.0 0.5 0 0LFM 400LFM 0 25 50 75 100 AMBIENT TEMPERATURE (C) 2.5 MAXIMUM LOAD CURRENT PER CHANNEL (A) MAXIMUM LOAD CURRENT PER CHANNEL (A) MAXIMUM LOAD CURRENT PER CHANNEL (A) 2.5 2.0 1.5 1.0 0.5 125 0 0LFM 400LFM 0 25 50 75 100 AMBIENT TEMPERATURE (C) 125 8078 G55 2.0 1.5 1.0 0.5 0 0LFM 400LFM 0 2.0 1.5 1.0 0.5 0LFM 400LFM 25 50 75 100 AMBIENT TEMPERATURE (C) 125 2.5 2.0 1.5 1.0 0.5 0 0LFM 400LFM 0 25 50 75 100 AMBIENT TEMPERATURE (C) 125 8078 G59 CISPR22 Class B Emissions 24VIN, fSW = 1.6MHz 5VOUT1 at 1.4A, 3.3VOUT2 at 1.4A Spread Spread Spectrum SpectrumOn, On,No NoEMI EMIFilter Filter Output Voltage Ripple DC2777A Demo Board HORIZONTAL VERTICAL CLASS B 3M RADIATED LIMIT 60 AMPLITUDE (dBuV/m) 125 8078 G57 8078 G58 70 25 50 75 100 AMBIENT TEMPERATURE (C) Derating, VIN = 36V, VOUT = 3.3V BIAS = 5V, DC2777A Demo Board Both Both Channels Channels at At Same Same Load Load MAXIMUM LOAD CURRENT PER CHANNEL (A) MAXIMUM LOAD CURRENT PER CHANNEL (A) 2.5 0 2.5 8078 G56 Derating, VIN = 24V, VOUT = 3.3V BIAS = 5V, DC2777A Demo Board Both Both Channels Channels at At Same Same Load Load 0 Derating, VIN = 12V, VOUT = 3.3V BIAS = 5V, DC2777A Demo Board Both Both Channels Channels at AtSame SameLoad Load Derating, VIN = 36V, VOUT = 1.5V BIAS = 5V, DC2777A Demo Board Both Channels at At Same Same Load Load Derating, VIN = 24V, VOUT = 1.5V BIAS = 5V, DC2777A Demo Board Channels at At Same Same Load Load BBoth oth Channels 50 5mV/DIV AC-COUPLED 40 30 20 10 1s/DIV 0 -10 0 200 400 600 FREQUENCY (MHz) 800 1000 8078 G61 VIN = 12V, VOUT = 3.3V IOUT = 1.4A, fSW = 1.2MHz 8078 G60 10 Rev. A For more information www.analog.com LTM8078 T TYPICAL PERFORMANCE CHARACTERISTICS A = 25C, operating per Table1,unless otherwise noted. Output Noise Sprectrum DC2777A, 100kHz Span VIN = 12V, VOUT = 3.3V IOUT OUT = 1.4A, FSW SW = 1.2MHz 100 100 90 90 80 80 80 70 70 70 60 50 40 30 20 10 OUTPUT NOISE (dBuV) 90 OUTPUT NOISE (dBuV) OUTPUT NOISE (dBuV) 100 Output Noise Sprectrum DC2777A, 10MHz Span VIN = 12V, VOUT = 3.3V IOUT = 1.4A, FSW SW = 1.2MHz OUT 60 50 40 30 20 10 60 50 40 30 20 10 0 0 0 -10 -10 -10 -20 10 20 30 40 50 60 70 FREQUENCY (kHz) 80 90 100 -20 0 1 2 8078 G62 3 4 5 6 7 FREQUENCY (MHz) 8 9 10 8078 G63 Output Noise Sprectrum DC2777A, 500MHz Span VIN = 12V, VOUT = 3.3V IOUT = 1.4A, FSW SW = 1.2MHz OUT -20 0 100 200 300 FREQUENCY (MHz) 400 500 8078 G64 CISPR25 Radiated Emission with Class 5 Average Limit DC2777A Demo Board, VIN = 12V, VOUT = 3.3V Two Channels Paralleled, IOUT = 2.8A, fSW = 1MHz Radiated Peak Two Channels Paralleled, IOUT = 2.8A, fSW = 1MHz 45 35 40 30 35 30 25 20 15 10 CLASS 5 PEAK LIMIT SPREAD SPECTURM MODE FIXED FREQUENCY MODE 5 0 0 200 400 600 FREQUENCY (MHz) 800 Radiated OUT Average 40 AMPLITUDE (dBuV/m) AMPLITUDE (dBuV/m) 50 1000 SW 25 20 15 10 5 0 CLASS 5 AVERAGE LIMIT SPREAD SPECTRUM MODE FIXED FREQUENCY MODE -5 -10 0 8078 G65 200 400 600 FREQUENCY (MHz) 800 1000 8078 G66 Rev. A For more information www.analog.com 11 LTM8078 PIN FUNCTIONS VIN1 (Pin A3): Input Power for the Channel 1 Regulator. The VIN1 bank powers the internal control circuitry for both channels and is monitored by under voltage lockout circuitry. The VIN1 voltage must be greater than 3.0V for either channel of the LTM8078 to operate. Decouple VIN1 to ground with an external, low ESR capacitor. See Table1 for recommended values. phase, duty cycle, and frequency as the SYNC waveform. In Burst Mode operation, the CLKOUT pin will be internally grounded. Float this pin if the CLKOUT function is not used. Do not drive this pin. VIN2 (Pin A4): Input Power for the Channel 2 Regulator. The VIN2 pin is monitored by under voltage lockout circuitry. The VIN1 voltage must be greater than 3.0V and VIN2 must be greater than 2V for proper VIN2 operation. Decouple VIN2 to ground with an external, low ESR capacitor. See Table1 for recommended values. PG1/PG2 (Pins B1, A2): The PGn pins are the open-drain outputs of an internal comparator. PGn remains low until the FBn pin is within 7.5% of the final regulation voltage, and there are no fault conditions. PGn is pulled low during VIN1 UVLO, VIN2 UVLO, thermal shutdown, or when the RUN pin is low. VOUT1/VOUT2 (Banks 1 and 2): Power Output for channels 1 and 2, Respectively. Apply the output filter capacitor and the output load between these pins and GND pins. GND (Bank 3, Pin A7): Tie these GND pins to a local ground plane below the LTM8078 and the circuit components. In most applications, the bulk of the heat flow out of the LTM8078 is through these pads, so the printed circuit design has a large impact on the thermal performance of the part. See the PCB Layout and Thermal Considerations sections for more details. Return the feedback divider (RFB) to this net. BIAS (Pin E7): The internal regulator will draw current from BIAS instead of VIN1 when BIAS is tied to a voltage higher than 3.2V. For output voltages of 3.3V and above this pin should be tied to VOUT. If this pin is tied to a supply other than VOUT connect a local bypass capacitor to this pin. CLKOUT (Pin D1): Synchronization Output. When SYNC>2.8V, the CLKOUT pin provides a waveform about 90 degrees out-of-phase with Channel 1. This allows synchronization with other regulators with up to four phases. When an external clock is applied to the SYNC pin, the CLKOUT pin will output a waveform with about the same 12 FB1/FB2 (Pins D7, C7): The LTM8078 regulates the FBn pins to 800mV. Connect the feedback resistor to this pin to set the output voltage. RT (Pin B7): Connect a resistor between RT and ground to set the switching frequency of both channels. Do not drive this pin. RUN (Pin A5): The LTM8078 is shut down when this pin is low and active when this pin is high. Tie to VINn if shutdown feature is not used. An external resistor divider from VINn can be used to program a VINn threshold below which the corresponding channel of the LTM8078 will shut down. Do not float this pin. OM (Pin C6): Output Mode. Tie this pin to the adjacent OMC pin when the two LTM8078 outputs are regulating at different voltages. Float this pin when the two LTM8078 outputs are in parallel. OMC (Pin D6): Output Mode Control. Float this pin when the two outputs of the LTM8078 are load sharing. Connect this pin to the OMC pin of other LTM8078s when multiple LTM8078s are load sharing. When not load sharing, tie this pin to the adjacent OM pin. That is, when the VOUT1 and VOUT2 are independent voltages, connect OM to OMC. If VOUT1 and VOUT2 are independent and OM and OMC are not connected together, the LTM8078 will not regulateproperly. Rev. A For more information www.analog.com LTM8078 PIN FUNCTIONS TRSS1/TRSS2 (Pin B6, A6): Output Tracking and SoftStart Pins. These pins allow user control of the output voltage ramp rate during startup. A TRSSn voltage below 0.8V forces the LTM8078 to regulate the FBn pin to equal the TRSSn pin voltage. When TRSSn is above 0.8V, the tracking function is disabled and the internal reference resumes control of the error amplifier. An internal 2A pull-up current on this pin allows a capacitor to program output voltage slew rate. This pin is pulled to ground during shutdown and fault conditions; use a series resistor if driving from a low impedance output. This pin may be left floating if the soft-start feature is not being used. SYNC (Pin C1): External Clock Synchronization Input. Ground this pin for low ripple Burst Mode operation at low output loads; this will also disable the CLKOUT function. Apply a DC voltage between 2.8V and 4V for spread spectrum modulation. Float the SYNC pin for forced continuous operation without spread spectrum modulation. Apply a clock source to the SYNC pin for synchronization to an external frequency. The LTM8078 will be in forced continuous mode when an external frequency is applied. BLOCK DIAGRAM VIN1 HOUSEKEEPING CIRCUITRY 0.2F RUN CURRENT MODE CONTROLLER TRSS1 1.5H VOUT1 249k 10pF 3.3nF SYNC UVLO FB1 PG1 RT PG2 VIN2 CLKOUT 0.1F TRSS2 CURRENT MODE CONTROLLER 1.5H VOUT2 BIAS 249k OMC 10pF 3.3nF FB2 GND OM 8078 BD Rev. A For more information www.analog.com 13 LTM8078 OPERATION The LTM8078 is a dual standalone non-isolated stepdown switching DC/DC power supply that can deliver a peak current of up to 2.5A per channel. The continuous current is determined by the internal operating temperature. It provides a precisely regulated output voltage programmable via one external resistor from 0.8V to 10V. The input voltage range for channel 1 is 3V to 40V, while the input voltage range for channel 2 is 2V to 40V. VIN1 must be 3V or above for either channel to operate. Given that the LTM8078 is a step-down converter, make sure that the input voltage is high enough to support the desired output voltage and load current. See simplified Block Diagram. The LTM8078 contains two current mode controllers, power switching elements, power inductors and a modest amount of input and output capacitance. The LTM8078 is a fixed frequency PWM regulator. The switching frequency is set by simply connecting the appropriate resistor value from the RT pin to GND. An internal regulator provides power to the control circuitry. This bias regulator normally draws power from the VIN1 pin, but if the BIAS pin is connected to an external voltage higher than 3.2V, bias power is drawn from the external source (typically the regulated output voltage). This improves efficiency. Tie BIAS to GND if it is not used. The TRSSn node acts as an auxiliary input to the error amplifier. The voltage at FB servos to the TRSS voltage until TRSS goes above 0.8V. Soft-start is implemented by generating a voltage ramp at the TRSS pin using an external capacitor which is charged by an internal constant current. Alternatively, driving the TRSS pin with a signal source or resistive network provides a tracking function. Do not drive the TRSS pin with a low impedance voltage source. See the Applications Information section for moredetails. The LTM8078 contains a power good comparator which trips when the FBn pin is at about 92% to 108% of its regulated value. The PGn output is an open-drain transistor that is off when the output is in regulation, allowing an external resistor to pull the PGn pin high. The PG1 signal is valid when VIN1 is above 3V. Similarly, the PG2 signal is valid when VIN2 is above 2V. The LTM8078 is equipped with a thermal shutdown that inhibits power switching at high junction temperatures. The activation threshold of this function is above the maximum temperature rating to avoid interfering with normal operation, so prolonged or repetitive operation under a condition in which the thermal shutdown activates may damage or impair the reliability of the device. To enhance efficiency, the LTM8078 automatically switches to Burst Mode operation in light or no load situations. Between bursts, all circuitry associated with controlling the output switch is shut down reducing the input supply current to just a few A. 14 Rev. A For more information www.analog.com LTM8078 APPLICATIONS INFORMATION For most applications, the design process is straight forward, summarized as follows: 1. Look at Table1 and find the row that has the desired input range and output voltage. 2. Apply the recommended CIN, COUT, RFB and RT values. 3. Connect BIAS as indicated. When using the LTM8078 with two different output voltages, the higher frequency recommended by Table1 will usually result in the best operation. While these component combinations have been tested for proper operation, it is incumbent upon the user to verify proper operation over the intended system's line, load and environmental conditions. Bear in mind that the maximum output current is limited by junction temperature, the relationship between the input and output voltage magnitude and other factors. Please refer to the graphs in the Typical Performance Characteristics section for guidance. The maximum frequency (and attendant RT value) at which the LTM8078 should be allowed to switch is given in Table1 in the Maximum fSW column, while the recommended frequency (and RT value) for optimal efficiency over the given input condition is given in the fSW column. There are additional conditions that must be satisfied if the synchronization function is used. Please refer to the Synchronization section for details. Capacitor Selection Considerations The CIN and COUT capacitor values in Table1 are the minimum recommended values for the associated operating conditions. Applying capacitor values below those indicated in Table1 is not recommended and may result in undesirable operation. Using larger values is generally acceptable, and can yield improved dynamic response. Again, it is incumbent upon the user to verify proper operation over the intended system's line, load and environmental conditions. Ceramic capacitors are small, robust and have very low ESR. However, not all ceramic capacitors are suitable. X5R and X7R types are stable over temperature and applied voltage and give dependable service. Other types, including Y5V and Z5U have very large temperature and voltage coefficients of capacitance. In an application circuit they may have only a small fraction of their nominal capacitance resulting in much higher output voltage ripple thanexpected. Ceramic capacitors are also piezoelectric. In Burst Mode operation, the LTM8078's switching frequency depends on the load current, and can excite a ceramic capacitor at audio frequencies, generating audible noise. Since the LTM8078 operates at a lower current limit during Burst Mode operation, the noise is typically very quiet to the casual ear. Table1. Recommended Component Values and Configuration (TA = 25C) VIN (NOTE 1) VOUT RFB (k) CIN (NOTE 2) COUT BIAS fSW (kHz) RT (k) MAX fSW (MHz) MIN RT (k) 3V to 40V 0.8V Open 1F 50V X5R 0805 2x 100F 4V X5R 0805 3.2V to 10V 500 68.1 1.2 24.9 3V to 40V 1V 1000 1F 50V X5R 0805 2x 100F 4V X5R 0805 3.2V to 10V 600 54.9 1.4 21.0 3V to 40V 1.2V 499 1F 50V X5R 0805 2x 100F 4V X5R 0805 3.2V to 10V 700 46.4 1.4 21.0 3.2V to 40V 1.5V 287 1F 50V X5R 0805 100F 4V X5R 0805 3.2V to 10V 900 34.8 1.4 21.0 3.2V to 40V 1.8V 200 1F 50V X5R 0805 100F 4V X5R 0805 3.2V to 10V 900 34.8 1.8 15.0 3.6V to 40V 2V 165 1F 50V X5R 0603 100F 4V X5R 0805 3.2V to 10V 1000 30.9 1.8 15.0 4.2V to 40V 2.5V 118 1F 50V X5R 0603 47F 4V X5R 0805 3.2V to 10V 1100 28.0 2 13.3 5V to 40V 3.3V 78.7 1F 50V X5R 0603 22F 6.3V X5R 0805 3.2V to 10V 1200 24.9 2.8 8.06 7V to 40V 5V 47.5 1F 50V X5R 0603 10F 6.3V X7R 0603 3.2V to 10V 1400 21.0 3 7.15 10.5V to 40V 8V 27.4 1F 50V X5R 0805 10F 10V X5R 0805 3.2V to 10V 2000 13.3 3 7.15 12V to 40V 10V 21.5 1F 50V X5R 0805 10F 16V X5R 1206 3.2V to 10V 2200 11.5 3 7.15 Note 1: The LTM8078 may be capable of the operating at lower input voltages but may skip switching cycles. Note 2: A bulk input capacitor is required. Rev. A For more information www.analog.com 15 LTM8078 APPLICATIONS INFORMATION If this audible noise is unacceptable, use a high performance electrolytic capacitor at the output. It may also be a parallel combination of a ceramic capacitor and a low cost electrolytic capacitor. A final precaution regarding ceramic capacitors concerns the maximum input voltage rating of the LTM8078. A ceramic input capacitor combined with trace or cable inductance forms a high-Q (underdamped) tank circuit. If the LTM8078 circuit is plugged into a live supply, the input voltage can ring to twice its nominal value, possibly exceeding the device's rating. This situation is easily avoided; see the Hot-Plugging Safely section. Frequency Selection The LTM8078 uses a constant frequency PWM architecture that can be programmed to switch from 300kHz to 3MHz by using a resistor tied from the RT pin to ground. Table2 provides a list of RT resistor values and their resultant frequencies. The resistors in the table are standard 1% E96 values. Table2. Switching Frequency vs RT Value fSW (MHz) 16 RT (k) 0.3 113 0.4 86.6 0.5 68.1 0.6 54.9 0.7 46.4 0.8 40.2 0.9 34.8 1.0 30.9 1.2 24.9 1.4 21.0 1.6 17.8 1.8 15.0 2.0 13.3 2.2 11.5 2.4 10.2 2.6 9.09 2.8 8.06 3.0 7.15 Operating Frequency Trade-Offs It is recommended that the user apply the optimal RT value given in Table1 for the input and output operating condition. When using the LTM8078 with two different output voltages, the higher frequency recommended by Table1 will usually result in the best operation. System level or other considerations, however, may necessitate another operating frequency. While the LTM8078 is flexible enough to accommodate a wide range of operating frequencies, a haphazardly chosen one may result in undesirable operation under certain operating or fault conditions. A frequency that is too high can reduce efficiency, generate excessive heat or even damage the LTM8078 if the output is overloaded or short-circuited. A frequency that is too low can result in a final design that has too much output ripple or too large of an output capacitor. BIAS Pin Considerations The BIAS pin is used to provide drive power for the internal power switching stage and operate other internal circuitry. For proper operation, it must be powered by at least 3.2V. If the output voltage is programmed to 3.2V or higher, BIAS may be simply tied to VOUT. If VOUT is less than 3.2V, BIAS can be tied to VIN or some other voltage source. If the BIAS pin voltage is too high, the efficiency of the LTM8078 may suffer. The optimum BIAS voltage is dependent upon many factors, such as load current, input voltage, output voltage and switching frequency. In all cases, ensure that the maximum voltage at the BIAS pin is less than 10V. If BIAS power is applied from a remote or noisy voltage source, it may be necessary to apply a decoupling capacitor locally to the pin. A 1F ceramic capacitor works well. The BIAS pin may also be tied to GND at the cost of a small degradation in efficiency. Maximum Load The maximum practical continuous load that the LTM8078 can drive per channel, while rated at 1.4A, actually depends upon both the internal current limit and the internal temperature. The internal current limit is designed to prevent damage to the LTM8078 in the case of overload or short-circuit. The internal temperature of the LTM8078 depends upon operating conditions such as the ambient Rev. A For more information www.analog.com LTM8078 APPLICATIONS INFORMATION temperature, the power delivered, and the heat sinking capability of the system. For example, if a single LTM8078 is configured to regulate at 1V, and channel 2 is turned off, channel 1 may continuously deliver 2.5A from 12VIN if the ambient temperature is controlled to less than 60C. This is quite a bit higher than the 1.4A continuous rating. Please see graphs in the Typical Performance Characteristics section. Similarly, if both channels of the LTM8078 are delivering 8VOUT and the ambient temperature is 100C, each channel will deliver at most 0.6A from 24VIN, which is less than the 1.4A continuous rating. Load Sharing The two LTM8078 channels may be paralleled to produce higher currents. To do this on two or more LTM8078, tie the VIN, VOUT, FB and OMC pins of all the paralleled channels/modules together (see Figure7). If only the two channels of a LTM8078 are paralleled, leave OMC and OM floating. To ensure that paralleled channels start up together, the TRSS pins may be tied together, as well. If it is inconvenient to tie the TRSS pins together, make sure that the same value soft-start capacitors are used for each Module regulator. When load sharing among n units and using a single RFB resistor, the value of the resistor is: RFB = 199.2 ,where RFB is in k n(VOUT - 0.8) When the LTM8078 outputs regulate independently, tie OM to OMC. Examples of load sharing applications are given in Figure4 through Figure6. Burst Mode Operation To enhance efficiency at light loads, the LTM8078 automatically switches to Burst Mode operation which keeps the output capacitor charged to the proper voltage whileminimizing the input quiescent current. During Burst Mode operation, the LTM8078 delivers single cycle bursts of current to the output capacitor followed by sleep periodswhere most of the internal circuitry is powered off and energy is delivered to the load by the output capacitor. During the sleep time, VIN and BIAS quiescent currents are greatly reduced, so, as the load current decreases towards a no load condition, the percentage of time that the LTM8078 operates in sleep mode increases and the average input current is greatly reduced, resulting in higher light load efficiency. Burst Mode operation is enabled by tying SYNC to GND. Minimum Input Voltage The LTM8078 is a step-down converter, so a minimum amount of headroom is required to keep the output in regulation. Keep the input above 3V to ensure proper operation. Voltage transients or ripple valleys that cause the input to fall below 3V may turn off the LTM8078. VIN1 must be above 3V for either channel to operate. If VIN1 is above 3V, channel 2 will operate as long as VIN2 is above 2V. Output Voltage Tracking and Soft-Start The LTM8078 allows the user to adjust its output voltage ramp rate by means of the TRSS pin. An internal 2A pulls up the TRSSn pin to about 2.4V. Putting an external capacitor on TRSSn enables soft starting the output to reduce current surges on the input supply. During the soft-start ramp the output voltage will proportionally track the TRSSn pin voltage. For output tracking applications, TRSSn can be externally driven by another voltage source. From 0V to 0.8V, the TRSSn voltage will override the internal 0.8V reference input to the error amplifier, thus regulating the FBn pin voltage to that of the TRSSn pin. When TRSSn is above 0.8V, tracking is disabled and the feedback voltage will regulate to the internal reference voltage. The TRSSn pin may be left floating if the function is not needed. An active pull-down circuit is connected to the TRSSn pin which will discharge the external soft-start capacitor in the case of fault conditions and restart the ramp when the faults are cleared. Fault conditions that clear the softstart capacitor are the RUNn pin transitioning low, VINn voltage falling too low, or thermal shutdown. Rev. A For more information www.analog.com 17 LTM8078 APPLICATIONS INFORMATION Pre-Biased Output As discussed in the Output Voltage Tracking and SoftStart section, the LTM8078 regulates the output to the FB voltage determined by the TRSSn pin whenever TRSSn is less than 0.8V. If the LTM8078 output is higher than the target output voltage, and SYNC is not held below 0.8V, the LTM8078 will attempt to regulate the output to the target voltage by returning a small amount of energy back to the input supply. If there is nothing loading the input supply, its voltage may rise. Take care that it does not rise so high that the input voltage exceeds the absolute maximum rating of the LTM8078. If SYNC is grounded, the LTM8078 will not return current to the input. Synchronization To select low ripple Burst Mode operation, tie the SYNC pin below about 0.8V (this can be ground or a logic low output). To synchronize the LTM8078 oscillator to an external frequency, connect a square wave (with about 20% to 80% duty cycle) to the SYNC pin. The square wave amplitude should have valleys that are below 0.8V and peaks above 1.5V. The LTM8078 may be synchronized over a 300kHz to 3MHz range. The LTM8078 will not enter Burst Mode operation at light output loads while synchronized to an external clock. The RT resistor should be chosen to set the switching frequency equal to or below the lowest synchronization input. For example, if the synchronization signal will be 500kHz and higher, the RT should be selected for500kHz or lower. The LTM8078 features spread spectrum operation to further reduce EMI/EMC emissions. To enable spread spectrum operation, apply between 2.8V and 4V to the SYNC pin. In this mode, triangular frequency modulation is used to vary the switching frequency between the value programmed by RT to about 20% higher than that value. The 18 modulation frequency is about 5kHz. For example, when the LTM8078 is programmed to 2MHz, the frequency will vary from 2MHz to 2.4MHz at a 5kHz rate. When spread spectrum operation is selected, Burst Mode operation is disabled, and the part may run in discontinuous mode. Shorted Input Protection Care needs to be taken in systems where the output is held high when the input to the LTM8078 is absent. This may occur in battery charging applications or in battery backup systems where a battery or some other supply is diode OR'ed with the LTM8078's output. If the VIN pin is allowed to float and the RUN pin is held high (either by a logic signal or because it is tied to VIN), then the LTM8078's internal circuitry pulls its quiescent current through its internal power switch. This is fine if your system can tolerate a few milliamps in this state. If you ground the RUN pin, the internal current drops to essentially zero. However, if the VIN pin is grounded while the output is held high, parasitic diodes inside the LTM8078 can pull large currents from the output through the VIN pin. Figure1 shows a circuit that runs only when the input voltage is present and that protects against a shorted or reversed input. VIN VIN LTM8078 RUN 8078 F01 Figure1. The Input Diode Prevents a Shorted Input from Discharging a Backup Battery Tied to the Output. It Also Protects the Circuit from a Reversed Input. The LTM8078 Runs Only When the Input Is Present Rev. A For more information www.analog.com LTM8078 APPLICATIONS INFORMATION PCB Layout Most of the headaches associated with PCB layout have been alleviated or even eliminated by the high level of integration of the LTM8078. The LTM8078 is nevertheless a switching power supply, and care must be taken to minimize EMI and ensure proper operation. Even with the high level of integration, you may fail to achieve specified operation with a haphazard or poor layout. See Figure2 for a suggested layout. Ensure that the grounding and heat sinking are acceptable. GND PLANE RT TRSS2 TRSS1 2. Place the CIN capacitor as close as possible to the VIN and GND connection of the LTM8078. 3. Place the COUT capacitor as close as possible to the VOUT and GND connection of the LTM8078. 4. Place the CIN and COUT capacitors such that their ground current flow directly adjacent to or underneath the LTM8078. 5. Connect all of the GND connections to as large a copper pour or plane area as possible on the top layer. Avoid breaking the ground connection between the external components and the LTM8078. 6. Use vias to connect the GND copper area to the board's internal ground planes. Liberally distribute these GND vias to provide both a good ground connection and thermal path to the internal planes of the printed circuit board. Pay attention to the location and density of the thermal vias in Figure2. The LTM8078 can benefit from the heat sinking afforded by vias that connect to internal GND planes at these locations, due to their proximity to internal power handling components. The optimum number of thermal vias depends upon the printed circuit board design. For example, a board might use very small via holes. It should employ more thermal vias than a board that uses larger holes. FB1 OM OMC BIAS COUT2 VOUT2 RUN CIN2 VIN2 VIN1 A few rules to keep in mind are: 1. Place the RFB and RT resistors as close as possible to their respective pins. FB2 CIN1 PG2 PG1 SYNC CLKOUT VOUT2 COUT1 GND PLANE GND/THERMAL VIA 8078 F02 Figure2. Layout Showing Suggested External Components, GND Plane and Thermal Vias Hot-Plugging Safely The small size, robustness and low impedance of ceramic capacitors make them an attractive option for the input bypass capacitor of LTM8078. However, these capacitors can cause problems if the LTM8078 is plugged into a live supply (see Application Note 88 for a complete discussion). The low loss ceramic capacitor combined with stray inductance in series with the power source forms an underdamped tank circuit, and the voltage at the VIN pin of the LTM8078 can ring to more than twice the nominal input voltage, possibly exceeding the LTM8078's rating and damaging the part. If the input supply is poorly controlled or the LTM8078 is hot-plugged into an energized supply, the input network should be designed to prevent this overshoot. This can be accomplished by installing a small resistor in series to VIN, but the most popular method of controlling input voltage overshoot is add an electrolytic bulk cap to the VIN net. This capacitor's relatively high equivalent series resistance damps the circuit and eliminates the voltage overshoot. The extra capacitor improves low frequency ripple filtering and can slightly improve the efficiency of the circuit, though it is likely to be the largest component in the circuit. Rev. A For more information www.analog.com 19 LTM8078 APPLICATIONS INFORMATION Thermal Considerations The LTM8078 output current may need to be derated if it is required to operate in a high ambient temperature. The amount of current derating is dependent upon the input voltage, output power and ambient temperature. The derating curves given in the Typical Performance Characteristics section can be used as a guide. These curves were generated by the LTM8078 mounted to a 58cm2 4-layer FR4 printed circuit board. Boards of other sizes and layer count can exhibit different thermal behavior, so it is incumbent upon the user to verify proper operation over the intended system's line, load and environmental operating conditions. For increased accuracy and fidelity to the actual application, many designers use FEA (Finite Element Analysis) or CFD (Computational Fluid Dynamics) to predict thermal performance. To that end, the Pin Configuration typically gives three dominant thermalcoefficients: 1. JA - Thermal resistance from junction to ambient 2. JCbot - Thermal resistance from junction to the bottom of the product case 3. JCtop - Thermal resistance from junction to top of the product case While the meaning of each of these coefficients may seem to be intuitive, JEDEC has defined each to avoid confusion and inconsistency. These definitions are given in JESD 51-12, and are quoted or paraphrased below: 1. JA is the natural convection junction-to-ambient air thermal resistance measured in a one cubic foot sealed enclosure. This environment is sometimes referred to as "still air" although natural convection causes the air to move. This value is determined with the part mounted to a JESD 51-9 defined test board, which does not reflect an actual application or viable operating condition. 2. JCbot is the junction-to-board thermal resistance with all of the component power dissipation flowing through the bottom of the package. In the typical Module regulator, the bulk of the heat flows out the 20 bottom of the package, but there is always heat flow out into the ambient environment. As a result, this thermal resistance value may be useful for comparing packages but the test conditions don't generally match the user's application. 3. JCtop is determined with nearly all of the component power dissipation flowing through the top of the package. As the electrical connections of the typical Module regulator are on the bottom of the package, it is rare for an application to operate such that most of the heat flows from the junction to the top of the part. As in the case of JCbot, this value may be useful for comparing packages but the test conditions don't generally match the user's application. Given these definitions, it should now be apparent that none of these thermal coefficients reflects an actual physical operating condition of a Module regulator. Thus, none of them can be individually used to accurately predict the thermal performance of the product. Likewise, it would be inappropriate to attempt to use any one coefficient to correlate to the junction temperature vs load graphs given in the product's data sheet. The only appropriate way to use the coefficients is when running a detailed thermal analysis, such as FEA, which considers all of the thermal resistances simultaneously. A graphical approximation of these dominant thermal resistances is given in Figure3. Some thermal resistance elements, such as heat flow out the side of the package, are not defined by the JEDEC standard and are not shown. The blue resistances are contained within the Module regulator, and the green are outside. The die temperature of the LTM8078 must be lower than the maximum rating, so care should be taken in the layout of the circuit to ensure good heat sinking of the LTM8078. The bulk of the heat flow out of the LTM8078 is through the bottom of the package and the pads into the printed circuit board. Consequently a poor printed circuit board design can cause excessive heating, resulting in impaired performance or reliability. Please refer to the PCB Layout section for printed circuit board design suggestions. Rev. A For more information www.analog.com LTM8078 APPLICATIONS INFORMATION Module DEVICE JA JUNCTION-TO-AMBIENT RESISTANCE JCtop JUNCTION-TO-CASE (TOP) RESISTANCE CASE (TOP)-TO-AMBIENT RESISTANCE JUNCTION AMBIENT JCbot JUNCTION-TO-CASE (BOTTOM) RESISTANCE CASE (BOTTOM)-TO-BOARD RESISTANCE BOARD-TO-AMBIENT RESISTANCE 8078 F03 Figure3. Graphical Representation of Thermal Coefficients, Including JESD51-12 Terms TYPICAL APPLICATION VIN 7V TO 40V VIN1 RUN 1F 24.9k FB1 RT (1.2MHz) OM OMC VIN2 1F LTM8078 VOUT1 78.7k 22F VOUT1 3.3V 1.4A VIN1 46.4k FB1 RT (700kHz) VOUT2 5V OM OMC BIAS FB2 VOUT1 RUN 1F GND VOUT2 LTM8078 100F FB2 GND VOUT2 100F BIAS 47.5k 249k VOUT3 1.2V 2.8A 10F VIN2 1F 8078 F07 PINS NOT USED: TRSS1, TRSS2, PG1, PG2, CLKOUT, SYNC Figure4. Cascade Two LTM8078 to Produce 3.3V/1.4A, 1.2V/2.8A from 7V to 40VIN, Both BIAS Pins Are Connected to VOUT2 Rev. A For more information www.analog.com 21 LTM8078 TYPICAL APPLICATIONS VIN 5V TO 40V VIN1 RUN LTM8078 1F 24.9k VOUT1 FB1 RT 200k 100F VOUT1 1.8V 1.4A GND (1.2MHz) OM VOUT2 OMC BIAS VIN2 FB2 1F VOUT2 3.3V 1.4A 78.7k 22F 8078 F04 PINS NOT USED: TRSS1, TRSS2, PG1, PG2, CLKOUT, SYNC Figure5. 1.8V/1.4A and 3.3V/1.4A from 5V to 40VIN, BIAS Is Connected to VOUT2 VIN 3.2V TO 40V VIN1 RUN LTM8078 VOUT 1.5V 2.8A VOUT1 FB2 1F FB1 34.8k 143k 100F RT (900kHz) GND OM OMC EXT. 3.3V VOUT2 100F BIAS VIN2 1F 8078 F05 PINS NOT USED: TRSS1, TRSS2, PG1, PG2, CLKOUT, SYNC Figure6. Parallel Two Channels to Produce 1.5V/2.8A from 3.2V to 40VIN, BIAS Is Connected to External 3.3V 22 Rev. A For more information www.analog.com LTM8078 TYPICAL APPLICATIONS VIN 5V TO 40V VIN1 RUN 1F VOUT 3.3V 5.6A VOUT1 BIAS 39.2k FB1 24.9k RT 22F FB2 (1.2MHz) OM VOUT2 CLKOUT 22F OMC VIN VIN2 GND 1F PINS NOT USED: TRSS1, TRSS2, PG1, PG2, SYNC VIN VIN1 RUN 1F VOUT1 BIAS 39.2k FB1 24.9k RT 22F FB2 (1.2MHz) OM VOUT2 OMC 22F SYNC VIN VIN2 GND 1F 8078 F06 PINS NOT USED: TRSS1, TRSS2, PG1, PG2, CLKOUT Figure7. Parallel All Channels of Two LTM8078 to Produce 3.3V/5.6A from 5V to 40V Input, BIAS Connected to VOUT PACKAGE DESCRIPTION Table3. LTM8078 Pinout (Sorted by Pin Number) Pin Pin Name Pin Pin Name Pin Pin Name Pin Pin Name Pin Pin Name Pin Pin Name Pin Pin Name A 1 GND B 1 PG1 C 1 SYNC D 1 CLKOUT E 1 GND F 1 VOUT1 G 1 VOUT1 A 2 PG2 B 2 GND C 2 GND D 2 GND E 2 GND F 2 VOUT1 G 2 VOUT1 A 3 VIN1 B 3 GND C 3 GND D 3 GND E 3 GND F 3 GND G 3 GND A 4 VIN2 B 4 GND C 4 GND D 4 GND E 4 GND F 4 GND G 4 GND A 5 RUN B 5 GND C 5 GND D 5 GND E 5 GND F 5 GND G 5 GND A 6 TRSS2 B 6 TRSS1 C 6 OM D 6 OMC E 6 GND F 6 VOUT2 G 6 VOUT2 A 7 GND B 7 RT C 7 FB2 D 7 FB1 E 7 BIAS F 7 VOUT2 G 7 VOUT2 Rev. A For more information www.analog.com 23 LTM8078 PACKAGE DESCRIPTION BGA Package 49-Lead (6.25mm x 6.25mm x 2.22mm) Z (Reference LTC DWG# 05-08-1518 Rev B) A1 2x A ccc Z aaa Z SEE NOTES DETAIL A A2 SEE NOTES 7 6 5 4 3 2 6 1 PIN 1 3 A PIN "A1" CORNER b b1 4 B MOLD CAP C SUBSTRATE D H1 H2 // bbb Z F D E e F DETAIL B G X e b ddd M Z X Y eee M Z Y E aaa Z Ob (49 PLACES) G DETAIL B PACKAGE SIDE VIEW PACKAGE TOP VIEW PACKAGE BOTTOM VIEW 2x NOTES: 1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M-1994 2. ALL DIMENSIONS ARE IN MILLIMETERS 2.4 1.6 DIMENSIONS 0.8 0.000 0.8 1.6 2.4 DETAIL A 2.4 0.40 0.025 O 49x 1.6 0.8 0.000 0.8 1.6 2.4 SUGGESTED PCB LAYOUT TOP VIEW SYMBOL A A1 A2 b b1 D E e F G H1 H2 aaa bbb ccc ddd eee MIN 2.02 0.30 1.72 0.45 0.37 NOM 2.22 0.40 1.82 0.50 0.40 6.25 6.25 0.80 4.80 4.80 0.32 REF 1.50 REF MAX 2.42 0.50 1.92 0.55 0.43 3 BALL DESIGNATION PER JEP95 4 DETAILS OF PIN #1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED WITHIN THE ZONE INDICATED. THE PIN #1 IDENTIFIER MAY BE EITHER A MOLD OR MARKED FEATURE NOTES BALL HT BALL DIMENSION PAD DIMENSION 5. PRIMARY DATUM -Z- IS SEATING PLANE 6 SUBSTRATE THK MOLD CAP HT 0.15 0.10 0.20 0.15 0.08 TOTAL NUMBER OF BALLS: 49 ! PACKAGE ROW AND COLUMN LABELING MAY VARY AMONG Module PRODUCTS. REVIEW EACH PACKAGE LAYOUT CAREFULLY LTMXXXXXX Module COMPONENT PIN "A1" TRAY PIN 1 BEVEL PACKAGE IN TRAY LOADING ORIENTATION BGA 49 0418 REV B 24 Rev. A For more information www.analog.com LTM8078 REVISION HISTORY REV DATE DESCRIPTION A 03/20 Added LTM8078IY in Order Information Added More Power Loss and Radiated EMI Graphs Added Bias Current (mA) vs Switching Frequency (MHz) Graph Added Output Voltage Ripple DC2777A Demo Board Graph Added Output Noise Spectrum DC2777A, 100kHz, 10MHz and 500MHz Span Performance Graphs Added CISPR25 Radiated Emission with Class 5 Average Limit DC2777A Demo Board Graphs PAGE NUMBER 2 5-6, 11 8 12 12 12 Rev. A Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license For is granted implication or otherwise under any patent or patent rights of Analog Devices. more by information www.analog.com 25 LTM8078 PACKAGE PHOTOGRAPH RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTM8074 40V, 1.2A Silent Switcher Module Regulator 3.2V VIN 40V, 0.8V VOUT 12V, 4mm x 4mm x 1.82mm BGA LTM8063 40V, 2A Step-Down Silent Switcher Module Regulator 3.2V VIN 40V, 0.8V VOUT 15V, 4mm x 6.25mm x 2.22mm BGA Package LTM8065 40V, 2.5A Step-Down Silent Switcher Module Regulator 3.4V VIN 40V, 0.97V VOUT 18V, 6.25mm x 6.25mm x 2.32mm BGA Package LTM8053 40V, 3.5A Step-Down Module Regulator 3.4V VIN 40V, 0.97V VOUT 15V, 6.25mm x 9mm x 3.32mm BGA LTM8003 40V, 3.5A, H-Grade, 150C Operation, FMAE-Compliant Pinout 3.4V VIN 40V, 0.97V VOUT 15V, IOUT = 3.5A, 6.25mm x 9mm x 3.32mm BGA LTM8052 36V, 5A CVCC Step-Down Module Regulator 6V VIN 36V, 1.2V VOUT 24V, Constant Voltage Constant Current, 11.25mm x 15mm x 2.82mm LGA, 11.25mm x 15mm x 3.42mm BGA LTM4613 36V, 8A Low EMI Step-Down Module Regulator 5V VIN 36V, 3.3V VOUT 15V, EN55022B Compliant, 15mm x 15mm x 4.32mm LGA, 15mm x 15mm x 4.92mm BGA. LTM8073 60V, 3A Step-Down Module Regulator 3.4V VIN 60V, 0.85V VOUT 15V, 6.25mm x 9mm x 3.32mm BGA LTM8071 60V, 5A Silent Switcher Module Regulator 3.6V VIN 60V, 0.97V VOUT 15V, 9mm x 11.25mm x 3.32mm BGA LTM4622 Dual 2.5A, 20V Step-Down Module Regulator 3.6V VIN 20V, 0.6V VOUT 5.5V, 6.25mm x 6.25mm x 1.82mm LGA, 6.25mm x 6.25mm x 2.42mm BGA LTM4642 Dual 4A, 20V Step-Down Module Regulator 4.5V VIN 20V, 0.6V VOUT 5.5V, 9mm x 11.25mm x 4.92mm BGA LTM4643 Quad 3A, 20V Step-Down Module Regulator 4V VIN 20V, 0.6V VOUT 3.3V, 9mm x 15mm x 1.82mm LGA, 9mm x 15mm x 2.42mm BGA LTM4644 Quad 4A, 14V Step-Down Module Regulator 4V VIN 14V, 0.6V VOUT 5.5V, 9mm x 15mm x 5.01mm BGA LTM8024 40VIN, Dual 3.5A or Single 7A Silent Switcher Module Regulator 3V VIN 40V, 0.8V VOUT 8V, 9mm x 11.25mm x 3.32mm BGAPackage 26 Rev. A 03/20 www.analog.com For more information www.analog.com ANALOG DEVICES, INC. 2019-2020