LT8640EUDC#PBF

LT8640/LT8640-1 42V, 5A Synchronous Step-Down Silent Switcher with 2.5µA Quiescent Current DESCRIPTION FEATURES Silent Switcher® Architecture nn Ultralow EMI/EMC Emissions nn Spread Spectrum Frequency Modulation nn High Efficiency at High Frequency nn Up to 96% Efficiency at 1MHz, 12V to 5V IN OUT nn Up to 95% Efficiency at 2MHz, 12V to 5V IN OUT nn Wide Input Voltage Range: 3.4V to 42V nn 5A Maximum Continuous Output, 7A Peak Transient Output nn Ultralow Quiescent Current Burst Mode® Operation nn 2.5µA I Regulating 12V to 3.3V Q IN OUT nn Output Ripple < 10mV P-P nn Fast Minimum Switch On-Time: 30ns nn Low Dropout Under All Conditions: 100mV at 1A nn Forced Continuous Mode (LT8640-1 Only) nn Safely Tolerates Inductor Saturation in Overload nn Adjustable and Synchronizable: 200kHz to 3MHz nn Peak Current Mode Operation nn Output Soft-Start and Tracking nn Small 18-Lead 3mm × 4mm QFN and Side Wettable QFN nn The LT®8640/LT8640-1 step-down regulator features Silent Switcher architecture designed to minimize EMI/EMC emissions while delivering high efficiency at frequencies up to 3MHz. An ultralow 2.5µA quiescent current—with the output in full regulation—enables applications requiring highest efficiency at very small load currents. The LT8640/LT8640-1 allows high VIN to low VOUT conversion at high frequency with a fast minimum top switch on-time of 30ns. The SYNC/MODE pin selects between Burst Mode operation, spread spectrum mode, synchronization to an external clock, and either pulse-skipping (LT8640) or forced continuous mode (LT8640-1). SYNC/ INTERNAL PACKAGE MODE ≠ 0 VC COMP H-GRADE CLKOUT CAPS LT8640 PulseInternal Skipping QFN Yes No No LT8640-1 QFN FCM Internal Yes No No LT8640S LQFN FCM Internal No Yes Yes LT8643S LQFN FCM External No Yes Yes LT8640S-2 LQFN FCM Internal Yes Yes No APPLICATIONS LT8643S-2 LQFN FCM External Yes Yes No Automotive and Industrial Supplies nn General Purpose Step-Down nn GSM Power Supplies All registered trademarks and trademarks are the property of their respective owners. Protected by U.S. patents, including 8823345. nn TYPICAL APPLICATION 100 5V 5A Step-Down Converter 3.00 2.63 95 4.7µF 1µF GND1 PG 10nF VIN2 GND2 LT8640/ LT8640-1 BST SYNC/MODE TR/SS fSW = 1MHz Document Feedback 1µF 0.1µF 3.3µH 4.7pF INTVCC RT VOUT 5V 5A SW BIAS 1µF 41.2k 90 1M 47µF FB GND 243k 85 1.88 80 1.50 1.13 75 70 POWER LOSS 65 60 0.5 8640 TA01a 2.25 EFFICIENCY 1 POWER LOSS (W) EN/UV VIN1 EFFICIENCY (%) VIN 5.5V TO 42V 12VIN to 5VOUT Efficiency 0.75 1MHz, L = 3.3µH 2MHz, L = 2.2µH 0.38 3MHz, L = 1µH 0 1.5 2 2.5 3 3.5 4 4.5 5 LOAD CURRENT (A) 8640 TA01b Rev.C For more information www.analog.com 1 LT8640/LT8640-1 PIN CONFIGURATION VIN, EN/UV, PG...........................................................42V BIAS...........................................................................25V FB, TR/SS ...................................................................4V SYNC Voltage ..............................................................6V Operating Junction Temperature Range (Note 2) LT8640E/LT8640-1E........................... –40°C to 125°C LT8640I/LT8640-1I............................. –40°C to 125°C LT8640H/LT8640-1H.......................... –40°C to 150°C Storage Temperature Range.......................–65 to 150°C SYNC/MODE 17 PG 20 19 18 FB GND TOP VIEW 16 TR/SS BIAS 1 INTVCC 2 15 RT BST 3 21 SW 13 VIN2 11 GND2 7 8 9 10 GND2 GND1 6 14 EN/UV SW VIN1 4 22 SW SW (Note 1) GND1 ABSOLUTE MAXIMUM RATINGS UDC AND UDCF PACKAGES 18-LEAD (3mm × 4mm) PLASTIC QFN θJA = 40°C/W, θJC(PAD) = 12°C/W (Note 3) EXPOSED PAD (PINS 21, 22) ARE SW, SHOULD BE SOLDERED TO PCB NOTE: PINS 5 AND 12 ARE REMOVED. CONFIGURATION DOES NOT MATCH JEDEC 20-LEAD PACKAGE OUTLINE ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT8640EUDC#PBF LT8640EUDC#TRPBF LGNJ 18-Lead (3mm × 4mm) Plastic QFN –40°C to 125°C LT8640IUDC#PBF LT8640IUDC#TRPBF LGNJ 18-Lead (3mm × 4mm) Plastic QFN –40°C to 125°C LT8640HUDC#PBF LT8640HUDC#TRPBF LGNJ 18-Lead (3mm × 4mm) Plastic QFN –40°C to 150°C LT8640EUDC-1#PBF LT8640EUDC-1#TRPBF LGVT 18-Lead (3mm × 4mm) Plastic QFN –40°C to 125°C LT8640IUDC-1#PBF LT8640IUDC-1#TRPBF LGVT 18-Lead (3mm × 4mm) Plastic QFN –40°C to 125°C LT8640HUDC-1#PBF LT8640HUDC-1#TRPBF LGVT 18-Lead (3mm × 4mm) Plastic QFN –40°C to 150°C LT8640EUDCF#PBF LT8640EUDCF#TRPBF LHJK 18-Lead (3mm × 4mm) Plastic Side Wettable QFN –40°C to 125°C LT8640IUDCF#PBF LT8640IUDCF#TRPBF LHJK 18-Lead (3mm × 4mm) Plastic Side Wettable QFN –40°C to 125°C LT8640EUDCF-1#PBF LT8640EUDCF-1#TRPBF LHGX 18-Lead (3mm × 4mm) Plastic Side Wettable QFN –40°C to 125°C LT8640IUDCF-1#PBF LT8640IUDCF-1#TRPBF LHGX 18-Lead (3mm × 4mm) Plastic Side Wettable QFN –40°C to 125°C Contact the factory for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. Tape and reel specifications. Some packages are available in 500 unit reels through designated sales channels with #TRMPBF suffix. Rev.C 2 For more information www.analog.com LT8640/LT8640-1 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. PARAMETER CONDITIONS Minimum Input Voltage VIN Quiescent Current TYP MAX l MIN 2.9 3.4 V l 0.75 0.75 3 10 µA µA l 1.7 1.7 4 10 µA µA 0.3 0.5 mA 21 220 50 350 µA µA 0.970 0.970 0.976 0.982 V V 0.004 0.02 %/V VEN/UV = 0V VEN/UV = 2V, Not Switching, VSYNC = 0V VEN/UV = 2V, Not Switching, VSYNC = 2V (LT8640 Only) VIN Current in Regulation VOUT = 0.97V, VIN = 6V, Output Load = 100µA VOUT = 0.97V, VIN = 6V, Output Load = 1mA l l Feedback Reference Voltage VIN = 6V, ILOAD = 0.5A VIN = 6V, ILOAD = 0.5A l VIN = 4.0V to 42V l Feedback Voltage Line Regulation Feedback Pin Input Current VFB = 1V BIAS Pin Current Consumption VBIAS = 3.3V, fSW = 2MHz Minimum On-Time ILOAD = 1.5A, SYNC = 0V ILOAD = 1.5A, SYNC = 3.3V 0.964 0.958 –20 l l Minimum Off-Time Oscillator Frequency RT = 221k RT = 60.4k RT = 18.2k Top Power NMOS On-Resistance ISW = 1A l l l 180 665 1.85 l Bottom Power NMOS On-Resistance VINTVCC = 3.4V, ISW = 1A SW Leakage Current VIN = 42V, VSW = 0V, 42V EN/UV Pin Threshold EN/UV Rising 7.5 35 30 50 50 ns ns 80 110 ns 210 700 2.00 240 735 2.15 kHz kHz MHz 10 mΩ 12.5 28 –15 l 0.94 EN/UV Pin Hysteresis 1.0 VEN/UV = 2V –20 PG Upper Threshold Offset from VFB VFB Falling l 5 PG Lower Threshold Offset from VFB VFB Rising l –5.25 PG Hysteresis mΩ µA 1.06 V mV 20 nA 7.5 10.25 % –8 –10.75 % 0.2 PG Leakage VPG = 3.3V PG Pull-Down Resistance VPG = 0.1V –40 SYNC/MODE Threshold SYNC/MODE DC and Clock Low Level Voltage SYNC/MODE Clock High Level Voltage SYNC/MODE DC High Level Voltage Spread Spectrum Modulation Frequency Range RT = 60.4k, VSYNC = 3.3V Spread Spectrum Modulation Frequency VSYNC = 3.3V l TR/SS Source Current 0.7 1.0 2.3 Fault Condition, TR/SS = 0.1V % 40 nA 700 2000 Ω 0.9 1.2 2.6 1.1 1.4 2.9 V V V 22 % 3 l 1.2 A 15 40 EN/UV Pin Current nA mA 67 Top Power NMOS Current Limit TR/SS Pull-Down Resistance 20 11 UNITS 1.9 200 kHz 2.6 µA Ω Rev.C For more information www.analog.com 3 LT8640/LT8640-1 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. PARAMETER CONDITIONS MIN TYP MAX LT8640-1 Output Sink Current in Forced Continuous Mode VFB = 1.01V, L = 6.8µH, RT = 60.4k 0.25 0.6 1 A LT8640-1 VIN to Disable Forced Continuous Mode VIN Rising 35 37 39 V LT8640-1 VFB Offset from Feedback Reference Voltage to Disable Forced Continuous Mode VFB Rising 7 9.5 12 % 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 LT8640E/LT8640-1E is guaranteed to meet performance specifications from 0°C to 125°C junction temperature. Specifications over the –40°C to 125°C operating junction temperature range are assured by design, characterization, and correlation with statistical process controls. The LT8640I/LT8640-1I is guaranteed over the full –40°C to 125°C operating junction temperature range. The LT8640H/LT8640-1H is guaranteed over the full –40°C to 150°C operating junction temperature range. High junction temperatures degrade operating lifetimes. Operating lifetime is derated at junction temperatures greater than 125°C. The junction temperature (TJ, in °C) is calculated from the ambient UNITS temperature (TA in °C) and power dissipation (PD, in Watts) according to the formula: TJ = TA + (PD • θJA) where θJA (in °C/W) is the package thermal impedance. Note 3: θ values determined per JEDEC 51-7, 51-12. See Applications Information section for information on improving the thermal resistance and for actual temperature measurements of a demo board in typical operating conditions. Note 4: This IC includes overtemperature protection that is intended to protect the device during overload conditions. Junction temperature will exceed 150°C when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature will reduce lifetime. Rev.C 4 For more information www.analog.com LT8640/LT8640-1 TYPICAL PERFORMANCE CHARACTERISTICS 12VIN to 3.3VOUT Efficiency vs Frequency EFFICIENCY 95 2.25 90 1.13 75 POWER LOSS 70 65 60 0.5 1 1.75 85 1.40 80 1.05 75 POWER LOSS 65 60 0.5 1 90 L = WE–LHMI1040 0.70 1MHz, L = 2.2μH 2MHz, L = 1μH 0.35 3MHz, L = 1μH 0 1.5 2 2.5 3 3.5 4 4.5 5 LOAD CURRENT (A) 8640 G01 1.8 75 70 60 55 0 0.5 Efficiency at 3.3VOUT Efficiency at 5VOUT 90 90 80 80 2.1 70 70 1.8 75 1.5 65 60 55 50 0 0.5 1 1.2 VIN = 12V 0.9 VIN = 24V 0.6 VIN = 36V fSW = 1MHz 0.3 L = IHLP3232DZ-01, 2.2μH 0 1.5 2 2.5 3 3.5 4 4.5 5 LOAD CURRENT (A) 100 60 50 40 fSW = 1MHz L = IHLP3232DZ-01, 4.7μH VIN = 12V VIN = 24V VIN = 36V 30 20 10 0 0.01 0.1 1 10 100 0.1 1 10 100 LOAD CURRENT (mA) 8640 G06 Reference Voltage VIN = 12V 0.977 EFFICIENCY (%) 88 86 VIN = 12V VOUT = 3.3V ILOAD = 2A L = IHLP3232DZ-01, 4.7μH VIN = 24V 85 80 75 VOUT = 5V ILOAD = 10mA L = IHLP3232DZ-01 70 3 REFERENCE VOLAGE (V) 90 90 65 1000 0.979 92 EFFICIENCY (%) 0 0.01 Burst Mode Operation Efficiency vs Inductor Value 94 2 1.5 2.5 0.5 1 SWITCHING FREQUENCY (MHz) fSW = 1MHz L = IHLP3232DZ-01, 4.7μH VIN = 12V VIN = 24V VIN = 36V 30 10 95 0 40 8640 G05 96 82 50 LOAD CURRENT (mA) Efficiency vs Frequency 84 60 20 1000 8640 G04 80 EFFICIENCY (%) 80 EFFICIENCY (%) 2.7 2.4 POWER LOSS (W) 95 70 1 8640 G03 90 POWER LOSS 1.2 VIN = 12V 0.9 VIN = 24V 0.6 VIN = 36V fSW = 1MHz 0.3 L = IHLP3232DZ-01, 3.3μH 0 1.5 2 2.5 3 3.5 4 4.5 5 LOAD CURRENT (A) 65 50 1.5 POWER LOSS 100 EFFICIENCY 2.1 80 3.0 85 2.4 EFFICIENCY 85 8640 G02 Efficiency at 3.3VOUT 100 EFFICIENCY (%) 2.7 2.10 EFFICIENCY 70 L = WE–LHMI1040 0.75 1MHz, L = 3.3µH 2MHz, L = 2.2µH 0.38 3MHz, L = 1µH 0 1.5 2 2.5 3 3.5 4 4.5 5 LOAD CURRENT (A) 3.0 95 POWER LOSS (W) 1.50 80 100 2.45 POWER LOSS (W) 1.88 85 POWER LOSS (W) EFFICIENCY (%) 90 2.63 EFFICIENCY (%) 95 Efficiency at 5VOUT 2.80 100 3.00 100 EFFICIENCY (%) 12VIN to 5VOUT Efficiency vs Frequency 1 2 3 4 5 6 INDUCTOR VALUE (µH) 7 0.973 0.971 0.969 0.967 0.965 0.963 8 8640 G08 8640 G07 0.975 0.961 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 8640 G09 Rev.C For more information www.analog.com 5 LT8640/LT8640-1 TYPICAL PERFORMANCE CHARACTERISTICS EN Pin Thresholds 0.12 0.10 1.02 0.10 1.00 0.99 0.98 0.08 CHANGE IN VOUT (%) EN RISING 1.01 CHANGE IN VOUT (%) EN THRESHOLD (V) Line Regulation Load Regulation 0.15 1.03 0.05 0 –0.05 0.97 EN FALLING 0.95 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) –0.15 0.02 0 –0.04 VOUT = 5V VIN = 12V R1/R2 = 100k/24.3k 0 0.5 1.5 2 2.5 3 3.5 LOAD CURRENT (A) 1 4 4.5 5 –0.08 5 10 15 20 25 30 35 INPUT VOLTAGE (V) 40 45 8640 G12 Top FET Current Limit vs Duty Cycle No-Load Supply Current 4.0 Top FET Current Limit 10.0 12.0 9.5 3.5 2.5 2.0 CURRENT LIMIT (A) CURRENT LIMIT (A) 9.0 3.0 8.5 8.0 7.5 11.0 VOUT = 3.3V L = 4.7µH IN REGULATION 0 5 10 15 20 25 30 35 INPUT VOLTAGE (V) 40 5% DC 10.0 9.0 7.0 1.5 1.0 VOUT = 5V ILOAD = 1A R1/R2 = 100k/24.3k –0.06 8640 G11 8640 G10 INPUT CURRENT (µA) 0.04 –0.02 –0.10 0.96 0.06 6.5 6.0 45 0 0.2 0.4 0.6 DUTY CYCLE 8640 G13 0.8 8.0 –50 –25 1 0 25 50 75 100 125 150 TEMPERATURE (°C) 8640 G14 8640 G15 Switch Drop SWITCH CURRENT = 1A 100 TOP SWITCH 75 50 BOTTOM SWITCH 25 0 25 50 75 100 125 150 TEMPERATURE (°C) 350 300 TOP SWITCH 250 200 150 100 37 34 31 28 50 0 VSYNC = FLOAT VSYNC = 0V 40 400 SWITCH DROP (mV) SWITCH DROP (mV) 43 450 125 0 –50 –25 Minimum On-Time Switch Drop 500 MINIMUM ON-TIME (ns) 150 BOTTOM SWITCH 0 1 4 2 3 SWITCH CURRENT (A) 8640 G16 5 25 –50 ILOAD = 2A –25 0 25 50 75 TEMPERATURE (°C) 100 125 8640 G18 8640 G17 Rev.C 6 For more information www.analog.com LT8640/LT8640-1 TYPICAL PERFORMANCE CHARACTERISTICS Switching Frequency Dropout Voltage 740 600 VIN = 5V VOUT SET TO REGULATE AT 5V L = IHLP3232DZ-01, 1µH FRONT PAGE APPLICATION VIN = 12V 1000 VOUT = 5V 300 200 100 SWITCHING FREQUENCY (kHz) 400 0 RT = 60.4k 730 SWITCHING FREQUENCY (kHz) DROPOUT VOLTAGE (mV) 500 Burst Frequency 1200 720 710 700 690 680 670 0 0.5 1.5 2 2.5 3 3.5 LOAD CURRENT (A) 1 4 4.5 660 –50 –25 5 0 20 600 1.0 500 400 300 20 25 30 35 INPUT VOLTAGE (V) 40 0 45 0 0.2 0.4 0.6 FB VOLTAGE (V) 0.8 PG THRESHOLD OFFSET FROM VREF (%) SS PIN CURRENT (µA) 1.9 1.8 1.7 1.6 1.5 25 50 75 100 125 150 TEMPERATURE (°C) 0 0.2 1.0 0.4 0.6 0.8 TR/SS VOLTAGE (V) 1.4 PG Low Thresholds –6.0 9.5 9.0 8.5 8.0 7.5 1.2 8640 G24 PG High Thresholds 2.0 0 0 1 10.0 VSS = 0.5V 1.4 –50 –25 0.4 8640 G23 Soft-Start Current 2.1 0.6 0.2 8640 G22 2.2 0.8 200 PG THRESHOLD OFFSET FROM VREF (%) 15 400 Soft-Start Tracking 100 10 100 200 300 LOAD CURRENT (mA) 1.2 FB VOLTAGE (V) 40 0 8640 G21 VOUT = 3.3V VIN = 12V VSYNC = 0V RT = 60.4k 700 SWITCHING FREQUENCY (kHz) LOAD CURRENT (mA) 800 FRONT PAGE APPLICATION VOUT = 5V fSW = 1MHz 5 200 Frequency Foldback 60 0 400 8640 G20 Minimum Load to Full Frequency (Pulse-Skipping Mode) 80 600 0 25 50 75 100 125 150 TEMPERATURE (°C) 8640 G19 100 800 FB RISING FB FALLING 7.0 6.5 6.0 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 8640 G26 8640 G25 –6.5 –7.0 –7.5 FB RISING –8.0 –8.5 FB FALLING –9.0 –9.5 –10.0 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 8640 G27 Rev.C For more information www.analog.com 7 LT8640/LT8640-1 TYPICAL PERFORMANCE CHARACTERISTICS RT Programmed Switching Frequency 3.6 225 8.5 3.4 200 125 100 75 BIAS PIN CURRENT (mA) 150 3.0 2.8 2.6 2.4 50 0 0.2 0.6 1.4 1.8 2.2 2.6 1 SWITCHING FREQUENCY (MHz) 2.0 –55 –25 3 95 65 35 TEMPERATURE (°C) 5 125 Bias Pin Current 80 10 5 2.6 1.4 1.8 2.2 0.6 1 SWITCHING FREQUENCY (MHz) 3 90 DC2202A DEMO BOARD VIN = 12V, fSW = 1MHz VIN = 24V, fSW = 1MHz VIN = 12V, fSW = 2MHz VIN = 24V, fSW = 2MHz 70 60 40 30 20 20 25 30 35 INPUT VOLTAGE (V) 40 0 45 70 60 50 40 30 20 10 0 1 2 3 LOAD CURRENT (A) 4 5 0 0 0.2 0.4 0.6 DUTY CYCLE OF 7A LOAD 0.8 8640 G33 8640 G32 Switching Waveforms, Burst Mode Operation Switching Waveforms IL 1A/DIV IL 500mA/DIV VSW 10V/DIV VSW 5V/DIV 8640 G34 15 DC2202A DEMO BOARD VIN = 12V VOUT = 5V fSW = 2MHz STANDBY LOAD = 0.25A 1KHz PULSED LOAD = 7A 80 50 Switching Waveforms, Full Frequency Continuous Operation VSW 5V/DIV 10 Case Temperature Rise vs 7A Pulsed Load 8640 G31 IL 1A/DIV 5 8640 G30 10 500ns/DIV FRONT PAGE APPLICATION 12VIN TO 5VOUT AT 1A 5.5 155 CASE TEMPERATURE RISE (°C) VBIAS = 5V VOUT = 5V VIN = 12V ILOAD = 1A 0 0.2 6.5 Case Temperature Rise CASE TEMPERATURE RISE (°C) BIAS PIN CURRENT (mA) 15 7.0 8640 G29 8640 G28 20 7.5 6.0 2.2 25 VBIAS = 5V VOUT = 5V ILOAD = 1A fSW = 1MHz 8.0 3.2 175 INPUT VOLTAGE (V) RT PIN RESISTOR (kΩ) Bias Pin Current VIN UVLO 250 5µs/DIV FRONT PAGE APPLICATION 12VIN TO 5VOUT AT 10mA VSYNC = 0V 8640 G35 500ns/DIV FRONT PAGE APPLICATION 36VIN TO 5VOUT AT 1A 8640 G36 Rev.C 8 For more information www.analog.com LT8640/LT8640-1 TYPICAL PERFORMANCE CHARACTERISTICS Transient Response; Load Current Stepped from 100mA (Burst Mode Operation) to 1.1A Transient Response; Load Current Stepped from 1A to 2A IL 1A/DIV IL 1A/DIV VOUT 100mV/DIV VOUT 200mV/DIV 50µs/DIV FRONT PAGE APPLICATION 1A TO 2A TRANSIENT 12VIN, 5VOUT COUT = 47µF 50µs/DIV FRONT PAGE APPLICATION 100mA (Burst Mode OPERATION) TO 1.1A TRANSIENT 12VIN, 5VOUT COUT = 47µF 8640 G37 Start-Up Dropout Performance Start-Up Dropout Performance VIN VIN 2V/DIV VIN VIN 2V/DIV VOUT VOUT 2V/DIV VOUT VOUT 2V/DIV 100ms/DIV 2.5Ω LOAD (2A IN REGULATION) 8640 G38 100ms/DIV 20Ω LOAD (250mA IN REGULATION) 8640 G39 8640 G40 Conducted EMI Performance 60 50 AMPLITUDE (dBµV) 40 30 20 10 0 -10 -20 FIXED FREQUENCY MODE SPREAD SPECTRUM MODE -30 -40 0 3 6 9 12 15 18 21 FREQUENCY (MHz) 24 27 30 8640 G41 DC2202A DEMO BOARD (WITH EMI FILTER INSTALLED) 14V INPUT TO 5V OUTPUT AT 4A, fSW = 2MHz Rev.C For more information www.analog.com 9 LT8640/LT8640-1 TYPICAL PERFORMANCE CHARACTERISTICS Radiated EMI Performance (CISPR25 Radiated Emission Test with Class 5 Peak Limits) 50 VERTICAL POLARIZATION PEAK DETECTOR 45 AMPLITUDE (dBµV/m) 40 35 30 25 20 15 10 5 CLASS 5 PEAK LIMIT FIXED FREQUENCY MODE SPREAD SPECTRUM MODE 0 -5 0 100 200 300 400 500 600 700 800 900 1000 FREQUENCY (MHz) 50 HORIZONTAL POLARIZATION PEAK DETECTOR 45 AMPLITUDE (dBµV/m) 40 35 30 25 20 15 10 5 CLASS 5 PEAK LIMIT FIXED FREQUENCY MODE SPREAD SPECTRUM MODE 0 -5 0 100 200 300 400 500 600 700 800 900 1000 FREQUENCY (MHz) DC2202A DEMO BOARD (WITH EMI FILTER INSTALLED) 14V INPUT TO 5V OUTPUT AT 4A, fSW = 2MHz 8640 G42 Rev.C 10 For more information www.analog.com LT8640/LT8640-1 PIN FUNCTIONS BIAS (Pin 1): The internal regulator will draw current from BIAS instead of VIN when BIAS is tied to a voltage higher than 3.1V. For output voltages of 3.3V to 25V this pin should be tied to VOUT. If this pin is tied to a supply other than VOUT use a 1µF local bypass capacitor on this pin. If no supply is available, tie to GND. INTVCC (Pin 2): Internal 3.4V Regulator Bypass Pin. The internal power drivers and control circuits are powered from this voltage. INTVCC maximum output current is 20mA. Do not load the INTVCC pin with external circuitry. INTVCC current will be supplied from BIAS if BIAS > 3.1V, otherwise current will be drawn from VIN. Voltage on INTVCC will vary between 2.8V and 3.4V when BIAS is between 3.0V and 3.6V. Decouple this pin to power ground with at least a 1µF low ESR ceramic capacitor placed close to the IC. BST (Pin 3): This pin is used to provide a drive voltage, higher than the input voltage, to the topside power switch. Place a 0.1µF boost capacitor as close as possible to the IC. VIN1 (Pin 4): The LT8640/LT8640-1 requires two 1µF small input bypass capacitors. One 1µF capacitor should be placed between VIN1 and GND1. A second 1µF capacitor should be placed between VIN2 and GND2. These capacitors must be placed as close as possible to the LT8640/ LT8640-1. A third larger capacitor of 2.2µF or more should be placed close to the LT8640/LT8640-1 with the positive terminal connected to VIN1 and VIN2, and the negative terminal connected to ground. See applications section for sample layout. GND1 (6, 7): Power Switch Ground. These pins are the return path of the internal bottom side power switch and must be tied together. Place the negative terminal of the input capacitor as close to the GND1 pins as possible. Also be sure to tie GND1 to the ground plane. See the Applications Information section for sample layout. SW (Pins 8, 9): The SW pins are the outputs of the internal power switches. Tie these pins together and connect them to the inductor and boost capacitor. This node should be kept small on the PCB for good performance and low EMI. GND2 (10, 11): Power Switch Ground. These pins are the return path of the internal bottom side power switch and must be tied together. Place the negative terminal of the input capacitor as close to the GND2 pins as possible. Also be sure to tie GND2 to the ground plane. See the Applications Information section for sample layout. VIN2 (Pin 13): The LT8640/LT8640-1 requires two 1µF small input bypass capacitors. One 1µF capacitor should be placed between VIN1 and GND1. A second 1µF capacitor should be placed between VIN2 and GND2. These capacitors must be placed as close as possible to the LT8640/ LT8640-1. A third larger capacitor of 2.2µF or more should be placed close to the LT8640/LT8640-1 with the positive terminal connected to VIN1 and VIN2, and the negative terminal connected to ground. See the Applications Information section for sample layout. EN/UV (Pin 14): The LT8640/LT8640-1 is shut down when this pin is low and active when this pin is high. The hysteretic threshold voltage is 1.00V going up and 0.96V going down. Tie to VIN if the shutdown feature is not used. An external resistor divider from VIN can be used to program a VIN threshold below which the LT8640/LT8640-1 will shut down. RT (Pin 15): A resistor is tied between RT and ground to set the switching frequency. TR/SS (Pin 16): Output Tracking and Soft-Start Pin. This pin allows user control of output voltage ramp rate during start-up. A TR/SS voltage below 0.97V forces the LT8640/LT8640-1 to regulate the FB pin to equal the TR/ SS pin voltage. When TR/SS is above 0.97V, the tracking function is disabled and the internal reference resumes control of the error amplifier. An internal 1.9µA pull-up current from INTVCC on this pin allows a capacitor to program output voltage slew rate. This pin is pulled to ground with an internal 200Ω MOSFET during shutdown and fault conditions; use a series resistor if driving from a low impedance output. This pin may be left floating if the tracking function is not needed. SYNC/MODE (Pin 17, LT8640 Only): This pin programs four different operating modes: 1) Burst Mode operation. Tie this pin to ground for Burst Mode operation at low output loads—this will result in ultralow quiescent current. 2) Pulse-skipping mode. This mode offers full frequency operation down to low output loads before pulse skipping occurs. Float this pin for pulse-skipping mode. When floating, pin leakage currents should be