LTC3374 8-Channel Parallelable 1A Buck DC/DCs FEATURES DESCRIPTION 8-Channel Independent Step-Down DC/DCs n Master-Slave Configurable for Up to 4A per Output Rail with a Single Inductor n Independent V Supplies for Each DC/DC IN (2.25V to 5.5V) n All DC/DCs Have 0.8V – V Output Range IN n Precision Enable Pin Thresholds for Autonomous Sequencing n1MHz to 3MHz Programmable/Synchronizable Oscillator Frequency (2MHz Default) n Die Temperature Monitor Output n Thermally Enhanced 38-Lead QFN (5mm × 7mm) and TSSOP Packages The LTC®3374 is a high efficiency multioutput power supply IC. The DC/DCs consist of eight synchronous buck converters (1A each) all powered from independent 2.25V to 5.5V input supplies. n APPLICATIONS General Purpose Multichannel Power Supplies Industrial/Automotive/Communications n n The DC/DCs may be used independently or in parallel to achieve higher currents of up to 4A per output with a shared inductor. The common buck switching frequency may be programmed with an external resistor, synchronized to an external oscillator, or set to a default internal 2MHz clock. The operating mode for all DC/DCs may be programmed via the MODE pin. To reduce input noise the buck converters are phased in 90° steps. Precision enable pin thresholds provide reliable power-up sequencing. The LTC3374 is available in a compact 38-lead 5mm × 7mm QFN package as well as a 38-lead TSSOP package. L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION 8-Channel 1A Multioutput Buck Regulator VIN1 BUCK1 VCC LTC3374 VIN2 BUCK2 0.8V TO VIN1 UP TO 1A Buck Efficiency vs ILOAD 100 MASTER 90 SLAVE EN1 MASTER EN2 EN3 • • EN4 • V SLAVE IN7 EN5 BUCK7 EN6 EN7 EN8 PGOOD_ALL MASTER TEMP MODE VIN8 SLAVE BUCK8 80 0.8V TO VIN2 UP TO 1A EFFICIENCY (%) 2.7V TO 5.5V 0.8V TO VIN7 UP TO 1A 70 60 50 SINGLE BUCK DUAL BUCK TRIPLE BUCK QUAD BUCK FORCED CONTINUOUS MODE VIN = 3.3V, VOUT = 1.8V fOSC = 1MHz, L = 3.3µH 40 30 20 10 0 0 0.8V TO VIN8 UP TO 1A 2000 1000 3000 LOAD CURRENT (mA) 4000 3374 TA01b SYNC RT 3374 TA01a 3374f For more information www.linear.com/LTC3374 1 LTC3374 TABLE OF CONTENTS Features...................................................... 1 Applications................................................. 1 Typical Application ......................................... 1 Description.................................................. 1 Absolute Maximum Ratings............................... 3 Pin Configuration........................................... 3 Order Information........................................... 3 Electrical Characteristics.................................. 4 Typical Performance Characteristics.................... 6 Pin Functions............................................... 11 Block Diagram.............................................. 13 Operation................................................... 14 Buck Switching Regulators...................................... 14 Buck Regulators with Combined Power Stages....... 14 Power Failure Reporting Via PGOOD_ALL Pin......... 15 Temperature Monitoring and Overtemperature Protection................................................................ 15 Programming the Operating Frequency................... 15 Applications Information................................. 17 Buck Switching Regulator Output Voltage and Feedback Network............................................. 17 Buck Regulators...................................................... 17 Combined Buck Regulators..................................... 17 Input and Output Decoupling Capacitor Selection... 17 PCB Considerations................................................. 17 Package Description...................................... 22 Typical Application........................................ 24 Related Parts............................................... 24 3374f 2 For more information www.linear.com/LTC3374 LTC3374 ABSOLUTE MAXIMUM RATINGS (Note 1) VIN1-8, FB1-8, EN1-8, VCC, PGOOD_ALL, SYNC, RT, MODE.......................................... –0.3V to 6V TEMP................... –0.3V to Lesser of (VCC + 0.3V) or 6V IPGOOD_ALL................................................................5mA Operating Junction Temperature Range (Notes 2, 3)............................................. –40°C to 150°C Storage Temperature Range................... –65°C to 150°C PIN CONFIGURATION TOP VIEW FB1 35 EN8 EN7 36 EN7 4 MODE 38 37 36 35 34 33 32 3 VCC 37 MODE EN1 TEMP 38 VCC 2 EN2 1 EN2 EN1 TEMP EN8 TOP VIEW FB1 1 31 FB8 VIN1 2 30 VIN8 VIN1 5 34 FB8 SW1 3 29 SW8 SW1 6 33 VIN8 SW2 4 28 SW7 SW2 7 32 SW8 VIN2 5 27 VIN7 VIN2 8 31 SW7 FB2 6 26 FB7 FB2 9 25 FB6 FB3 10 39 GND FB3 7 VIN3 8 24 VIN6 SW3 9 23 SW6 SW4 10 22 SW5 VIN4 11 21 VIN5 20 FB5 FB4 12 VIN3 11 28 FB6 27 VIN6 SW4 13 26 SW6 VIN4 14 25 SW5 FB4 15 24 VIN5 EN4 16 23 FB5 EN3 17 22 EN5 PGOOD_ALL 18 21 EN6 EN5 EN6 RT SYNC PGOOD_ALL EN3 EN4 29 FB7 SW3 12 13 14 15 16 17 18 19 UHF PACKAGE 38-LEAD (5mm × 7mm) PLASTIC QFN TJMAX = 150°C, θJA = 34°C/W EXPOSED PAD (PIN 39) IS GND, MUST BE SOLDERED TO PCB 30 VIN7 39 GND SYNC 19 20 RT FE PACKAGE 38-LEAD PLASTIC TSSOP TJMAX = 150°C, θJA = 25°C/W EXPOSED PAD (PIN 39) IS GND, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC3374EUHF#PBF LTC3374EUHF#TRPBF 3374 38-Lead (5mm × 7mm) Plastic QFN –40°C to 125°C LTC3374IUHF #PBF LTC3374IUHF#TRPBF 3374 38-Lead (5mm × 7mm) Plastic QFN –40°C to 125°C LTC3374HUHF #PBF LTC3374HUHF#TRPBF 3374 38-Lead (5mm × 7mm) Plastic QFN –40°C to 150°C LTC3374EFE #PBF LTC3374EFE#TRPBF LTC3374EFE 38-Lead Plastic TSSOP –40°C to 125°C LTC3374IFEF #PBF LTC3374IFEF#TRPBF LTC3374IFE 38-Lead Plastic TSSOP –40°C to 125°C LTC3374HFE #PBF LTC3374HFE#TRPBF LTC3374HFE 38-Lead Plastic TSSOP –40°C to 150°C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. Consult LTC Marketing for information on nonstandard lead based finish parts. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ For more information www.linear.com/LTC3374 3374f 3 LTC3374 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VCC = VIN1-8 = 3.3V, unless otherwise specified. SYMBOL PARAMETER VVCC VCC Voltage Range VVCC_UVLO Undervoltage Threshold on VCC VCC Voltage Falling VCC Voltage Rising IVCC_ALLOFF VCC Input Supply Current All Switching Regulators in Shutdown IVCC VCC Input Supply Current At Least 1 Buck Active SYNC = 0V, RT = 400k, VFB_BUCK = 0.85V SYNC = 2MHz fOSC Internal Oscillator Frequency VRT = VCC, SYNC = 0V VRT = VCC, SYNC = 0V RRT = 400k, SYNC = 0V fSYNC Synchronization Frequency VSYNC SYNC Level High SYNC Level Low VRT RT Servo Voltage CONDITIONS MIN l 2.7 l l 2.35 2.45 l l tLOW, tHIGH > 40ns RRT = 400k 1.8 1.75 1.8 TYP MAX 5.5 V 2.45 2.55 2.55 2.65 V V 8 18 µA 45 200 75 275 µA µA 2 2 2 2.2 2.25 2.2 MHZ MHz MHz 3 MHz 1 l l 1.2 l 780 800 UNITS 0.4 V V 820 mV Temperature Monitor VTEMP(ROOM) TEMP Voltage at 25°C 150 mV ∆VTEMP/°C VTEMP Slope 6.75 mV/°C OT Overtemperature Shutdown 165 °C OT Hyst Overtemperature Hysteresis 10 °C Temperature Rising 1A Buck Regulators VBUCK Buck Input Voltage Range VOUT Buck Output Voltage Range VIN_UVLO Undervoltage Threshold on VIN VIN Voltage Falling VIN Voltage Rising IVIN_BUCK Burst Mode® Operation Forced Continuous Mode Operation Shutdown Input Current Shutdown Input Current VFB_BUCK = 0.85V (Note 4) ISW_BUCK = 0µA, VFB_BUCK = 0V All Switching Regulators in Shutdown At Least One Other Buck Active IFWD PMOS Current Limit (Note 5) VFB Feedback Regulation Voltage IFB Feedback Leakage Current l l l l VFB_BUCK = 0.85V 2.25 5.5 V VFB VIN V 2.05 2.15 2.15 2.25 V V 18 400 0 1 50 550 1 2 µA µA µA µA 2.0 2.3 2.7 A 780 800 820 mV 50 nA 1.95 2.05 –50 DMAX Maximum Duty Cycle VFB_BUCK = 0V RPMOS PMOS On-Resistance ISW_BUCK = 100mA 265 mΩ RNMOS NMOS On-Resistance ISW_BUCK = 100mA 280 mΩ ILEAKP PMOS Leakage Current EN_BUCK = 0 –2 2 µA ILEAKN NMOS Leakage Current EN_BUCK = 0 –2 2 µA tSS Soft-Start Time VPGOOD(FALL) Falling PGOOD Threshold Voltage VPGOOD(HYS) PGOOD Hysteresis l 100 % 1 ms 92.5 % 1 % Buck Regulators Combined IFWD2 PMOS Current Limit 2 Buck Converters Combined (Note 5) 4.6 A IFWD3 PMOS Current Limit 3 Buck Converters Combined (Note 5) 6.9 A IFWD4 PMOS Current Limit 4 Buck Converters Combined (Note 5) 9.2 A 3374f 4 For more information www.linear.com/LTC3374 LTC3374 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VCC = VIN1-8 = 3.3V, unless otherwise specified. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Interface Logic Pins (PBGOOD_ALL, MODE) IOH Output High Leakage Current PGOOD_ALL 5.5V at Pin –1 VOL Output Low Voltage PGOOD_ALL 3mA into Pin VIH Input High Threshold MODE l VIL Input Low Threshold MODE l 1 0.1 0.4 1.2 µA V V 0.4 V Interface Logic Pins (EN1, EN2, EN3, EN4, EN5, EN6, EN7, EN8) VHI_ALLOFF Enable Rising Threshold All Regulators Disabled l VEN_HYS Enable Falling Hysteresis Enable Rising Threshold At Least One Regulator Enabled l VHI IEN Enable Pin Leakage Current EN = VCC = VIN = 5.5V 400 730 1200 60 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 LTC3374 is tested under pulsed load conditions such that TJ ≈ TA. The LTC3374E is guaranteed to meet specifications from 0°C to 85°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 LTC3374I is guaranteed over the –40°C to 125°C operating junction temperature range and the LTC3374H is guaranteed over the –40°C to 150°C operating junction temperature range. High junction temperatures degrade operating lifetimes; operating lifetime is derated for junction temperatures greater than 125°C. Note that the maximum ambient temperature consistent with these specifications is determined by specific operating conditions in conjunction with board layout, the rated package thermal impedance and other environmental factors. The junction temperature (TJ in °C) is calculated from ambient 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. 380 –1 400 mV mV 420 mV 1 µA Note 3: The LTC3374 includes overtemperature protection which protects the device during momentary overload conditions. Junction temperatures will exceed 150°C when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature may impair device reliability. Note 4: Static current, switches not switching. Actual current may be higher due to gate charge losses at the switching frequency. Note 5: The current limit features of this part are intended to protect the IC from short term or intermittent fault conditions. Continuous operation above the maximum specified pin current rating may result in device degradation over time. 3374f For more information www.linear.com/LTC3374 5 LTC3374 TYPICAL PERFORMANCE CHARACTERISTICS Buck VIN Undervoltage Threshold vs Temperature 2.30 2.65 2.25 2.60 VCC RISING 2.55 2.50 VCC FALLING 2.45 60 ALL REGULATORS 55 IN SHUTDOWN 50 2.20 VIN RISING 2.15 2.10 VIN FALLING 2.05 2.40 2.30 –50 –25 1.90 –50 –25 25 50 75 100 125 150 TEMPERATURE (°C) 0 25 50 75 100 125 150 TEMPERATURE (°C) fOSC (MHz) IVCC (µA) 240 VCC = 3.3V 200 VCC = 2.7V 160 0 25 50 75 100 125 150 TEMPERATURE (°C) 0 –50 –25 0 1.95 VCC = 5.5V VCC = 3.3V VCC = 2.7V 0 25 50 75 100 125 150 TEMPERATURE (°C) 3374 G05 3374 G06 Oscillator Frequency vs VCC 2.20 VRT = VCC 2.15 2.15 2.10 2.10 2.05 2.05 fOSC (MHz) fOSC (MHz) 2.00 1.80 –50 –25 25 50 75 100 125 150 TEMPERATURE (°C) Default Oscillator Frequency vs Temperature 2.00 1.95 1.90 VCC = 5.5V VCC = 3.3V VCC = 2.7V 1.85 1.80 –50 –25 2.05 1.85 3374 G04 2.20 RRT = 402k 1.90 80 40 0 –50 –25 25 50 75 100 125 150 TEMPERATURE (°C) 2.10 120 25 0 2.15 VCC = 5.5V 280 IVCC (µA) 2.20 320 VCC = 2.7V VCC = 2.7V RT Programmed Oscillator Frequency vs Temperature AT LEAST ONE BUCK ENABLED 360 SYNC = 2MHz 50 VCC = 5.5V 3374 G03 400 VCC = 5.5V VCC = 3.3V 0 –50 –25 VCC Supply Current vs Temperature AT LEAST ONE BUCK ENABLED SYNC = 0V FB = 850mV VCC = 3.3V 20 3374 G02 VCC Supply Current vs Temperature 75 30 25 5 3374 G01 100 35 10 1.95 0 45 40 15 2.00 2.35 125 VCC Supply Current vs Temperature IVCC_ALLOFF (µA) 2.70 UV THRESHOLD (V) UV THRESHOLD (V) VCC Undervoltage Threshold vs Temperature 0 25 50 75 100 125 150 TEMPERATURE (°C) VRT = VCC 2.00 RRT = 402k 1.95 1.90 1.85 1.80 2.7 3374 G07 3.1 3.5 3.9 4.3 VCC (V) 4.7 5.1 5.5 3374 G08 3374f 6 For more information www.linear.com/LTC3374 LTC3374 TYPICAL PERFORMANCE CHARACTERISTICS VCC = 3.3V 3.5 1200 3.0 1000 2.5 800 VTEMP (mV) 2.0 1.5 Enable Threshold vs Temperature 900 850 400 ACTUAL VTEMP 200 0.5 0 –200 EN FALLING 600 550 450 IDEAL VTEMP 0 50 415 20 40 60 80 100 120 TEMPERATURE (°C) 400 –50 –25 140 0 25 50 75 100 125 150 TEMPERATURE (°C) 3374 G11 Buck VIN Supply Current vs Temperature 550 Burst Mode OPERATION FB = 850mV 40 IVIN_BURST (µA) 410 405 EN RISING EN FALLING 390 30 VIN = 5.5V 20 VIN = 2.25V VIN = 3.3V 10 385 FORCED CONTINUOUS MODE 500 FB = 0V 450 VIN = 5.5V 400 VIN = 3.3V 350 VIN = 2.25V 300 250 200 150 100 50 0 –50 –25 25 50 75 100 125 150 TEMPERATURE (°C) 0 3374 G12 1.86 0 25 50 75 100 125 150 TEMPERATURE (°C) 3374 G13 3374 G14 PMOS Current Limit vs Temperature VOUT vs Temperature 1.88 0 –50 –25 25 50 75 100 125 150 TEMPERATURE (°C) 2.6 FORCED CONTINUOUS MODE LOAD = 0mA VIN = 3.3V 2.5 1.84 1.82 1.80 1.78 2.4 VIN = 5.5V IFWD (A) 0 VOUT (V) EN THRESHOLD (mV) 650 Buck VIN Supply Current vs Temperature 420 380 –50 –25 EN RISING 700 3374 G10 Enable Pin Precision Threshold vs Temperature 395 750 500 3374 G09 400 ALL REGULATORS DISABLED VCC = 3.3V 800 600 1.0 0 250 300 350 400 450 500 550 600 650 700 750 800 RRT (kΩ) VTEMP vs Temperature IVIN_FORCED_CONTINUOUS (µA) fOSC (MHz) 1400 EN THRESHOLD (mV) Oscillator Frequency vs RT 4.0 VIN = 2.25V VIN = 3.3V 2.3 2.2 1.76 2.1 1.74 1.72 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 2.0 –50 –25 3374 G15 0 25 50 75 100 125 150 TEMPERATURE (°C) 3374 G16 3374f For more information www.linear.com/LTC3374 7 LTC3374 TYPICAL PERFORMANCE CHARACTERISTICS 550 500 500 VIN = 2.25V 400 VIN = 3.3V 350 VIN = 5.5V 300 100 80 450 VIN = 2.25V 400 VIN = 3.3V 350 300 250 0 1A Buck Efficiency vs ILOAD 2A Buck Efficiency vs ILOAD 20 10 1 10 100 LOAD CURRENT (mA) 90 70 FORCED CONTINUOUS MODE 60 50 40 VOUT = 1.8V fOSC = 2MHz L = 2.2µH VIN = 2.25V VIN = 3.3V VIN = 5.5V 30 20 10 0 1000 10 100 LOAD CURRENT (mA) 1 FORCED CONTINUOUS MODE 60 50 40 VOUT = 2.5V fOSC = 2MHz L = 2.2µH VIN = 2.7V VIN = 3.3V VIN = 5.5V 30 10 0 10 100 LOAD CURRENT (mA) 1 3374 G21 3A Buck Efficiency vs ILOAD 1000 3374 G22 3A Buck Efficiency vs ILOAD 100 100 90 90 80 80 Burst Mode OPERATION 70 60 FORCED CONTINUOUS MODE 50 40 VOUT = 1.8V fOSC = 2MHz L = 2.2µH VIN = 2.25V VIN = 3.3V VIN = 5.5V 30 20 10 1 10 100 LOAD CURRENT (mA) 1000 EFFICIENCY (%) EFFICIENCY (%) 70 20 1000 3374 G20 0 Burst Mode OPERATION 80 EFFICIENCY (%) EFFICIENCY (%) EFFICIENCY (%) VOUT = 2.5V fOSC = 2MHz L = 2.2µH VIN = 2.7V VIN = 3.3V VIN = 5.5V 30 0 2A Buck Efficiency vs ILOAD Burst Mode OPERATION 80 50 1000 100 90 90 Burst Mode 80 OPERATION 40 10 100 LOAD CURRENT (mA) 1 3374 G19 100 FORCED CONTINUOUS MODE VOUT = 1.8V fOSC = 2MHz L = 2.2µH VIN = 2.25V VIN = 3.3V VIN = 5.5V 30 3374 G18 100 60 50 40 0 25 50 75 100 125 150 TEMPERATURE (°C) 3374 G17 70 FORCED CONTINUOUS MODE 60 10 200 –50 –25 25 50 75 100 125 150 TEMPERATURE (°C) 0 70 20 VIN = 5.5V 250 200 –50 –25 Burst Mode OPERATION 90 EFFICIENCY (%) 550 450 1A Buck Efficiency vs ILOAD NMOS RDS(ON) vs Temperature 600 RDS(ON) (mΩ) RDS(ON) (mΩ) PMOS RDS(ON) vs Temperature 600 Burst Mode OPERATION 70 60 50 40 VOUT = 2.5V fOSC = 2MHz L = 2.2µH VIN = 2.7V VIN = 3.3V VIN = 5.5V 30 20 10 0 FORCED CONTINUOUS MODE 1 3374 G23 10 100 LOAD CURRENT (mA) 1000 3374 G24 3374f 8 For more information www.linear.com/LTC3374 LTC3374 TYPICAL PERFORMANCE CHARACTERISTICS 1A Buck Efficiency vs Frequency (Forced Continuous Mode) 4A Buck Efficiency vs ILOAD 100 100 100 90 90 90 80 80 60 50 VOUT = 1.8V fOSC = 2MHz L = 2.2µH VIN = 2.25V VIN = 3.3V VIN = 5.5V 20 10 0 1 60 FORCED CONTINUOUS MODE 50 40 VOUT = 2.5V fOSC = 2MHz L = 2.2µH VIN = 2.7V VIN = 3.3V VIN = 5.5V 30 20 10 0 10 100 1000 LOAD CURRENT (mA) 3374 G25 70 EFFICIENCY (%) IL = 20mA 60 50 40 VOUT = 1.8V VIN = 3.3V fOSC = 2MHz L = 3.3µH 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 FREQUENCY (MHz) 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 FREQUENCY (MHz) Burst Mode OPERATION 60 50 3374 G27 40 30 10 0 1.812 FORCED CONTINUOUS MODE 1.804 10 100 LOAD CURRENT (mA) 1 VIN = 5.5V 1.808 VOUT = 1.8V VIN = 3.3V fOSC = 1MHz L = 3.3µH fOSC = 2MHz L = 2.2µH fOSC = 3MHz L = 1µH 20 3 3 fOSC = 2MHz 1.816 L = 2.2µH VIN = 3.3V 1.800 1.796 VIN = 2.25V 1.792 1.788 DROPOUT 1.784 1.780 1000 1 10 100 1.820 1.815 1.812 3374 G30 1A Buck Regulator Line Regulation (Forced Continuous Mode) 1.820 fOSC = 2MHz 1.816 L = 2.2µH 1000 IL (mA) 3374 G29 4A Buck Regulator Load Regulation (Forced Continuous Mode) fOSC = 2MHz L = 2.2µH 1.810 VIN = 5.5V 1.805 1.804 VIN = 3.3V 1.800 1.796 1.800 IL = 100mA IL = 500mA 1.795 VIN = 2.25V 1.792 1.790 1.788 DROPOUT 1.784 1.780 1 1.820 3374 G28 1.808 VOUT = 1.8V IL = 100mA fOSC = 2MHz L = 3.3µH 1A Buck Regulator Load Regulation (Forced Continuous Mode) VOUT (V) 0 VOUT (V) EFFICIENCY (%) 80 70 10 0 90 IL = 500mA 20 30 10 100 80 30 40 1A Buck Efficiency vs ILOAD (Across Operating Frequency) IL = 100mA 90 50 3374 G26 1A Buck Efficiency vs Frequency (Forced Continuous Mode) 100 60 20 10 100 1000 LOAD CURRENT (mA) 1 VIN = 3.3V VIN = 5.5V 70 VOUT (V) FORCED CONTINUOUS 40 MODE 30 70 VIN = 2.25V 80 Burst Mode OPERATION EFFICIENCY (%) Burst Mode OPERATION 70 EFFICIENCY (%) EFFICIENCY (%) 4A Buck Efficiency vs ILOAD 1 10 100 1.785 1000 1.780 2.25 2.75 3.25 3.75 4.25 4.75 5.25 VIN (V) IL (mA) 3374 G31 3374 G32 3374f For more information www.linear.com/LTC3374 9 LTC3374 TYPICAL PERFORMANCE CHARACTERISTICS 4A Buck Regulator No-Load Start-Up Transient (Forced Continuous Mode) 1A Buck Regulator No-Load Start-Up Transient (Burst Mode Operation) VOUT 500mV/DIV INDUCTOR CURRENT 500mA/DIV EN 2V/DIV 1A Buck Regulator, Transient Response (Burst Mode Operation) VOUT 500mV/DIV VOUT 100mV/DIV AC-COUPLED INDUCTOR CURRENT 500mA/DIV INDUCTOR CURRENT 200mA/DIV 0mA EN 2V/DIV VIN = 3.3V 200µs/DIV 3374 G33 VIN = 3.3V 1A Buck Regulator, Transient Response (Forced Continuous Mode) VOUT 100mV/DIV AC-COUPLED INDUCTOR CURRENT 200mA/DIV 0mA 50µs/DIV LOAD STEP = 100mA TO 700mA VIN = 3.3V VOUT = 1.8V 3374 G36 200µs/DIV 3374 G34 50µs/DIV LOAD STEP = 100mA TO 700mA VIN = 3.3V VOUT = 1.8V 4A Buck Regulator, Transient Response (Forced Continuous Mode) 4A Buck Regulator, Transient Response (Burst Mode Operation) VOUT 100mV/DIV AC-COUPLED VOUT 100mV/DIV AC-COUPLED INDUCTOR CURRENT 1A/DIV 0mA INDUCTOR CURRENT 1A/DIV 0mA 50µs/DIV LOAD STEP = 400mA TO 2.8A VIN = 3.3V VOUT = 1.8V 3374 G37 3374 G35 50µs/DIV LOAD STEP = 400mA TO 2.8A VIN = 3.3V VOUT = 1.8V 3374 G38 3374f 10 For more information www.linear.com/LTC3374 LTC3374 PIN FUNCTIONS (QFN/TSSOP) FB1 (Pin 1/Pin 4): Buck Regulator 1 Feedback Pin. Receives feedback by a resistor divider connected across the output. VIN1 (Pin 2/Pin 5): Buck Regulator 1 Input Supply. Bypass to GND with a 10µF or larger ceramic capacitor. SW1 (Pin 3/Pin 6): Buck Regulator 1 Switch Node. External inductor connects to this pin. SW2 (Pin 4/Pin 7): Buck Regulator 2 Switch Node. External inductor connects to this pin. VIN2 (Pin 5/Pin 8): Buck Regulator 2 Input Supply. Bypass to GND with a 10µF or larger ceramic capacitor. May be driven by an independent supply or must be shorted to VIN1 when buck regulator 2 is combined with buck regulator 1 for higher current. FB2 (Pin 6/Pin 9): Buck Regulator 2 Feedback Pin. Receives feedback by a resistor divider connected across the output. Connecting FB2 to VIN2 combines buck regulator 2 with buck regulator 1 for higher current. Up to four converters may be combined in this way. FB3 (Pin 7/Pin 10): Buck Regulator 3 Feedback Pin. Receives feedback by a resistor divider connected across the output. Connecting FB3 to VIN3 combines buck regulator 3 with buck regulator 2 for higher current. Up to four converters may be combined in this way. VIN3 (Pin 8/Pin 11): Buck Regulator 3 Input Supply. Bypass to GND with a 10µF or larger ceramic capacitor. May be driven by an independent supply or must be shorted to VIN2 when buck regulator 3 is combined with buck regulator 2 for higher current. SW3 (Pin 9/Pin 12): Buck Regulator 3 Switch Node. External inductor connects to this pin. SW4 (Pin 10/Pin 13): Buck Regulator 4 Switch Node. External inductor connects to this pin. VIN4 (Pin 11/Pin 14): Buck Regulator 4 Input Supply. Bypass to GND with a 10µF or larger ceramic capacitor. May be driven by an independent supply or must be shorted to VIN3 when buck regulator 4 is combined with buck regulator 3 for higher current. FB4 (Pin 12/Pin 15): Buck Regulator 4 Feedback Pin. Receives feedback by a resistor divider connected across the output. Connecting FB4 to VIN4 combines buck regulator 4 with buck regulator 3 for higher current. Up to four converters may be combined in this way. EN4 (Pin 13/Pin 16): Buck Regulator 4 Enable Input. Active high. EN3 (Pin 14/Pin 17): Buck Regulator 3 Enable Input. Active high. PGOOD_ALL (Pin 15/Pin 18): PGOOD Status Pin. Opendrain output. When the regulated output voltage of any enabled switching regulator is more than 7.5% below its programmed level, this pin is driven LOW. When all buck regulators are disabled PGOOD_ALL is driven LOW. SYNC (Pin 16/Pin 19): Oscillator Synchronization Pin. Driving SYNC with an external clock signal will synchronize all switchers to the applied frequency. The slope compensation is automatically adapted to the external clock frequency. The absence of an external clock signal will enable the frequency programmed by the RT pin. SYNC should be held at ground if not used. Do not float. RT (Pin 17/Pin 20): Oscillator Frequency Pin. This pin provides two modes of setting the switching frequency. Connecting a resistor from RT to ground will set the switching frequency based on the resistor value. If RT is tied to VCC the internal 2MHz oscillator will be used. Do not float. EN6 (Pin 18/Pin 21): Buck Regulator 6 Enable Input. Active high. EN5 (Pin 19/Pin 22): Buck Regulator 5 Enable Input. Active high. FB5 (Pin 20/Pin 23): Buck Regulator 5 Feedback Pin. Receives feedback by a resistor divider connected across the output. Connecting FB5 to VIN5 combines buck regulator 5 with buck regulator 4 for higher current. Up to four converters may be combined in this way. 3374f For more information www.linear.com/LTC3374 11 LTC3374 PIN FUNCTIONS (QFN/TSSOP) VIN5 (Pin 21/Pin 24): Buck Regulator 5 Input Supply. Bypass to GND with a 10µF or larger ceramic capacitor. May be driven by an independent supply or must be shorted to VIN4 when buck regulator 5 is combined with buck regulator 4 for higher current. VIN8 (Pin 30/Pin 33): Buck Regulator 8 Input Supply. Bypass to GND with a 10µF or larger ceramic capacitor. May be driven by an independent supply or must be shorted to VIN7 when buck regulator 8 is combined with buck regulator 7 for higher current. SW5 (Pin 22/Pin 25): Buck Regulator 5 Switch Node. External inductor connects to this pin. FB8 (Pin 31/Pin 34): Buck Regulator 8 Feedback Pin. Receives feedback by a resistor divider connected across the output. Connecting FB8 to VIN8 combines buck regulator 8 with buck regulator 7 for higher current. Up to four converters may be combined in this way. SW6 (Pin 23/Pin 26): Buck Regulator 6 Switch Node. External inductor connects to this pin. VIN6 (Pin 24/Pin 27): Buck Regulator 6 Input Supply. Bypass to GND with a 10µF or larger ceramic capacitor. May be driven by an independent supply or must be shorted to VIN5 when buck regulator 6 is combined with buck regulator 5 for higher current. EN8 (Pin 32/Pin 35): Buck Regulator 8 Enable Input. Active high. EN7 (Pin 33/Pin 36): Buck Regulator 7 Enable Input. Active high. FB6 (Pin 25/Pin 28): Buck Regulator 6 Feedback Pin. Receives feedback by a resistor divider connected across the output. Connecting FB6 to VIN6 combines buck regulator 6 with buck regulator 5 for higher current. Up to four converters may be combined in this way. MODE (Pin 34/Pin 37): Logic Input. MODE enables Burst Mode functionality for all the buck switching regulators when the pin is set low. When the pin is set high, all the buck switching regulators will operate in forced continuous mode. FB7 (Pin 26/Pin 29): Buck Regulator 7 Feedback Pin. Receives feedback by a resistor divider connected across the output. Connecting FB7 to VIN7 combines buck regulator 7 with buck regulator 6 for higher current. Up to four converters may be combined in this way. VCC (Pin 35/Pin 38): Internal Bias Supply. Bypass to GND with a 10µF or larger ceramic capacitor. VIN7 (Pin 27/Pin 30): Buck Regulator 7 Input Supply. Bypass to GND with a 10µF or larger ceramic capacitor. May be driven by an independent supply or must be shorted to VIN6 when buck regulator 7 is combined with buck regulator 6 for higher current. SW7 (Pin 28/Pin 31): Buck Regulator 7 Switch Node. External inductor connects to this pin. SW8 (Pin 29/Pin 32): Buck Regulator 8 Switch Node. External inductor connects to this pin. TEMP (Pin 36/Pin 1): Temperature Indication Pin. TEMP outputs a voltage of 150mV (typical) at room temperature. The TEMP voltage will change by 6.75mV/°C (typical) giving an external indication of the LTC3374 internal die temperature. EN2 (Pin 37/Pin 2): Buck Regulator 2 Enable Input. Active high. EN1 (Pin 38/Pin 3): Buck Regulator 1 Enable Input. Active high. GND (Exposed Pad Pin 39/Exposed Pad Pin 39): Ground. The exposed pad must be connected to a continuous ground plane on the printed circuit board directly under the LTC3374 for electrical contact and rated thermal performance. 3374f 12 For more information www.linear.com/LTC3374 LTC3374 BLOCK DIAGRAM (Pin numbers reflect QFN package) TOP LOGIC VCC 35 15 PGOOD_ALL SYNC 16 REF, CLK RT 17 8 PGOOD TEMP 36 BANDGAP, OSCILLATOR, UV, OT TEMP MONITOR 34 MODE 30 VIN8 VIN1 2 SW1 3 FB1 1 BUCK REGULATOR 1 1A BUCK REGULATOR 8 1A MASTER/SLAVE LINES MASTER/SLAVE LINES 27 VIN7 VIN2 5 FB2 6 BUCK REGULATOR 2 1A BUCK REGULATOR 7 1A MASTER/SLAVE LINES 24 VIN6 BUCK REGULATOR 3 1A BUCK REGULATOR 6 1A MASTER/SLAVE LINES 25 FB6 MASTER/SLAVE LINES 21 VIN5 VIN4 11 FB4 12 23 SW6 18 EN6 EN3 14 SW4 10 26 FB7 MASTER/SLAVE LINES VIN3 8 FB3 7 28 SW7 33 EN7 EN2 37 SW3 9 31 FB8 32 EN8 EN1 38 SW2 4 29 SW8 BUCK REGULATOR 4 1A BUCK REGULATOR 5 1A EN4 13 22 SW5 20 FB5 19 EN5 MASTER/SLAVE LINES GND (EXPOSED PAD) 39 3374 BD 3374f For more information www.linear.com/LTC3374 13 LTC3374 OPERATION Buck Switching Regulators The LTC3374 contains eight monolithic 1A synchronous buck switching regulators. All of the switching regulators are internally compensated and need only external feedback resistors to set the output voltage. The switching regulators offer two operating modes: Burst Mode operation (when the MODE pin is set low) for higher efficiency at light loads and forced continuous PWM mode (when the MODE pin is set high) for lower noise at light loads. The MODE pin collectively sets the operating mode for all enabled buck switching regulators. In Burst Mode operation at light loads, the output capacitor is charged to a voltage slightly higher than its regulation point. The regulator then goes into sleep mode, during which time the output capacitor provides the load current. In sleep most of the regulator’s circuitry is powered down, helping conserve input power. When the output capacitor droops below its programmed value, the circuitry is powered on and another burst cycle begins. The sleep time decreases as load current increases. In Burst Mode operation, the regulator will burst at light loads whereas at higher loads it will operate at constant frequency PWM mode operation. In forced continuous mode, the oscillator runs continuously and the buck switch currents are allowed to reverse under very light load conditions to maintain regulation. This mode allows the buck to run at a fixed frequency with minimal output ripple. Each buck switching regulator has its own VIN, SW, FB and EN pins to maximize flexibility. The enable pins have two different enable threshold voltages that depend on the operating state of the LTC3374. With all regulators disabled, the enable pin threshold is set to 730mV (typical). Once any regulator is enabled, the enable pin thresholds of the remaining regulators are set to a bandgap-based 400mV and the EN pins are each monitored by a precision comparator. This precision EN threshold may be used to provide event-based sequencing via feedback from other previously enabled regulators. All buck regulators have forward and reverse-current limiting, soft-start to limit inrush current during start-up, and short-circuit protection. The buck switching regulators are phased in 90° steps to reduce noise and input ripple. The phase step determines the fixed edge of the switching sequence, which is when the PMOS turns on. The PMOS off (NMOS on) phase is subject to the duty cycle demanded by the regulator. Bucks 1 and 2 are set to 0°, bucks 3 and 4 are set to 90°, bucks 5 and 6 are set to 180°, and bucks 7 and 8 are set to 270°. In shutdown all SW nodes are high impedance. The buck regulator enable pins may be tied to VOUT voltages, through a resistor divider, to program power-up sequencing. Buck Regulators with Combined Power Stages Up to four adjacent buck regulators may be combined in a master-slave configuration by connecting their SW pins together, connecting their VIN pins together, and connecting the higher numbered bucks’ FB pin(s) to the input supply. The lowest numbered buck is always the master. In Figure 1, buck regulator 1 is the master. The feedback network connected to the FB1 pin programs the output voltage to 1.2V. The FB2 pin is tied to VIN1-2, which configures buck regulator 2 as the slave. The SW1 and SW2 pins must be tied together, as must the VIN1 and VIN2 pins. The slave buck control circuitry draws no current. The enable of the master buck (EN1) controls the VIN L1 VIN1 SW1 COUT BUCK REGULATOR 1 (MASTER) EN1 VOUT 1.2V 2A 400k FB1 800k VIN VIN2 SW2 BUCK REGULATOR 2 (SLAVE) FB2 EN2 VIN 3374 F01 Figure 1. Buck Regulators Configured as Master-Slave 3374f 14 For more information www.linear.com/LTC3374 LTC3374 OPERATION operation of the combined bucks; the enable of the slave regulator (EN2) must be tied to ground. Any combination of 2, 3, or 4 adjacent buck regulators may be combined to provide either 2A, 3A, or 4A of average output load current. For example, buck regulator 1 and buck regulator 2 may run independently, while buck regulators 3 and 4 may be combined to provide 2A, while buck regulators 5 through 8 may be combined to provide 4A. Buck regulator 1 is never a slave, and buck regulator 8 is never a master. 15 unique output power stage configurations are possible to maximize application flexibility. Power Failure Reporting Via PGOOD_ALL Pin Power failure conditions are reported back via the PGOOD_ALL pin. All buck switching regulators have an internal power good (PGOOD) signal. When the regulated output voltage of an enabled switcher rises above 93.5% of its programmed value, the PGOOD signal will transition high. When the regulated output voltage falls below 92.5% of its programmed value, the PGOOD signal is pulled low. If any internal PGOOD signal stays low for greater than 100µs, then the PGOOD_ALL pin is pulled low, indicating to a microprocessor that a power failure fault has occurred. The 100µs filter time prevents the pin from being pulled low due to a transient. An error condition that pulls the PGOOD_ALL pin low is not latched. When the error condition goes away, the PGOOD_ALL pin is released and is pulled high if no other error condition exists. If no buck switching regulators are enabled, then PGOOD_ALL will be pulled low. Temperature Monitoring and Overtemperature Protection To prevent thermal damage to the LTC3374 and its surrounding components, the LTC3374 incorporates an overtemperature (OT) function. When the LTC3374 die temperature reaches 165°C (typical) all enabled buck switching regulators are shut down and remain in shutdown until the die temperature falls to 155°C (typical). The temperature may be read back by the user by sampling the TEMP pin analog voltage. The temperature, T, indicated by the TEMP pin voltage is given by: T= VTEMP +19mV •1°C 6.75mV (1) If temperature monitoring functionality is not desired, then the user may shut down the temperature monitor in order to lower quiescent current (15µA typical) by tying TEMP to VCC. In this case all enabled buck switching regulators are still shut down when the die temperature reaches 165°C (typical) and remain in shutdown until the die temperature falls to 155°C (typical). If none of the buck switching regulators are enabled, then the temperature monitor is also shut down to further reduce quiescent current. Programming the Operating Frequency Selection of the operating frequency is a trade-off between efficiency and component size. High frequency operation allows the use of smaller inductor and capacitor values. Operation at lower frequencies improves efficiency by reducing internal gate charge losses but requires larger inductance values and/or capacitance to maintain low output voltage ripple. The operating frequency for all of the LTC3374 regulators is determined by an external resistor that is connected between the RT pin and ground. The operating frequency can be calculated by using the following equation: 8 •1011 • ΩHz fOSC = RT (2) While the LTC3374 is designed to function with operating frequencies between 1MHz and 3MHz, it has safety clamps that will prevent the oscillator from running faster than 4MHz (typical) or slower than 250kHz (typical). Tying the RT pin to VCC sets the oscillator to the default internal operating frequency of 2MHz (typical). 3374f For more information www.linear.com/LTC3374 15 LTC3374 OPERATION The LTC3374’s internal oscillator can be synchronized through an internal PLL circuit, to an external frequency by applying a square wave clock signal to the SYNC pin. During synchronization, the top MOSFET/turn-on of buck switching regulators 1 and 2 are locked to the rising edge of the external frequency source. All other buck switching regulators are locked to the appropriate phase of the external frequency source (see Buck Switching Regulators). The synchronization frequency range is 1MHz to 3MHz. After detecting an external clock on the first rising edge of the SYNC pin, the PLL starts up at the current frequency being programmed by the RT pin. The internal PLL then requires a certain number of periods to gradually settle until the frequency at SW matches the frequency and phase of SYNC. When the external clock is removed the LTC3374 needs approximately 5µs to detect the absence of the external clock. During this time, the PLL will continue to provide clock cycles before it recognizes the lack of a SYNC input. Once the external clock removal has been identified, the oscillator will gradually adjust its operating frequency to match the desired frequency programmed at the RT pin. SYNC should be connected to ground if not used. 3374f 16 For more information www.linear.com/LTC3374 LTC3374 APPLICATIONS INFORMATION Buck Switching Regulator Output Voltage and Feedback Network The output voltage of the buck switching regulators is programmed by a resistor divider connected from the switching regulator’s output to its feedback pin and is given by VOUT = VFB(1 + R2/R1) as shown in Figure 2. Typical values for R1 range from 40k to 1M. The buck regulator transient response may improve with optional capacitor CFF that helps cancel the pole created by the feedback resistors and the input capacitance of the FB pin. Experimentation with capacitor values between 2pF and 22pF may improve transient response. VOUT BUCK SWITCHING REGULATOR R2 FB CFF + COUT (OPTIONAL) R1 3374 F02 Figure 2. Feedback Components Buck Regulators All eight buck regulators are designed to be used with inductors ranging from 1µH to 3.3µH depending on the lowest switching frequency that the buck regulator must operate at. To operate at 1MHz a 3.3µH inductor should be used, while to operate at 3MHz a 1µH inductor may be used. Table 1 shows some recommended inductors for the buck regulators. The input supply needs to be decoupled with a 22µF capacitor while the output needs to be decoupled with a 47µF capacitor for a 2A combined buck regulator. Likewise for 3A and 4A configurations the input and output capacitance must be scaled up to account for the increased load. Refer to the Capacitor Selection section for details on selecting a proper capacitor. In many cases, any extra unused buck converters may be used to increase the efficiency of the active regulators. In general the efficiency will improve for any regulators running close to their rated load currents. If there are unused regulators, the user should look at their specific applications and current requirements to decide whether to add extra stages. Input and Output Decoupling Capacitor Selection The LTC3374 has individual input supply pins for each buck switching regulator and a separate VCC pin that supplies power to all top level control and logic. Each of these pins must be decoupled with low ESR capacitors to GND. These capacitors must be placed as close to the pins as possible. Ceramic dielectric capacitors are a good compromise between high dielectric constant and stability versus temperature and DC bias. Note that the capacitance of a capacitor deteriorates at higher DC bias. It is important to consult manufacturer data sheets and obtain the true capacitance of a capacitor at the DC bias voltage it will be operated at. For this reason, avoid the use of Y5V dielectric capacitors. The X5R/X7R dielectric capacitors offer good overall performance. The input supply needs to be decoupled with a 10µF capacitor while the output needs to be decoupled with a 22µF capacitor. Refer to the Capacitor Selection section for details on selecting a proper capacitor. The input supply voltage Pins 2/5, 5/8, 8/11, 11/14, 21/24, 24/27, 27/30, 30/33, and 35/38 (QFN/TSSOP packages) all need to be decoupled with at least 10µF capacitors. Combined Buck Regulators When laying out the printed circuit board, the following list should be followed to ensure proper operation of the LTC3374: A single 2A buck regulator is available by combining two adjacent 1A buck regulators together. Likewise a 3A or 4A buck regulator is available by combining any three or four adjacent buck regulators respectively. Tables 2, 3, and 4 show recommended inductors for these configurations. PCB Considerations 1.The exposed pad of the package (Pin 39) should connect directly to a large ground plane to minimize thermal and electrical impedance. 3374f For more information www.linear.com/LTC3374 17 LTC3374 APPLICATIONS INFORMATION Table 1. Recommended Inductors for 1A Buck Regulators PART NUMBER L (µH) MAX IDC (A) MAX DCR (mΩ) SIZE IN mm (L × W × H) 1.0 3 38 3 × 3.6 × 1.2 1239AS-H-1R0N 1 2.5 65 2.5 × 2.0 × 1.2 XFL4020-222ME 2.2 3.5 23.5 4 × 4 × 2.1 1277AS-H-2R2N 2.2 2.6 84 3.2 × 2.5 × 1.2 IHLP1212BZER2R2M-11 2.2 3 46 3 × 3.6 × 1.2 XFL4020-332ME 3.3 2.8 38.3 4 × 4 × 2.1 IHLP1212BZER3R3M-11 3.3 2.7 61 3 × 3.6 × 1.2 SIZE IN mm (L × W × H) IHLP1212ABER1R0M-11 MANUFACTURER Vishay Toko CoilCraft Toko Vishay CoilCraft Vishay Table 2. Recommended Inductors for 2A Buck Regulators PART NUMBER L (µH) MAX IDC (A) MAX DCR (mΩ) XFL4020-102ME 1.0 5.1 11.9 4 × 4 × 2.1 1 9 27 4.45 × 4.06 × 1.8 XAL4020-222ME 2.2 5.6 38.7 4 × 4 × 2.1 FDV0530-2R2M 2.2 5.3 15.5 6.2 × 5.8 × 3 IHLP2020BZER2R2M-11 2.2 5 37.7 5.49 × 5.18 × 2 XAL4030-332ME 3.3 5.5 28.6 4 × 4 × 3.1 FDV0530-3R3M 3.3 4.1 34.1 6.2 × 5.8 × 3 SIZE IN mm (L × W × H) 74437324010 MANUFACTURER CoilCraft Wurth Elektronik CoilCraft Toko Vishay CoilCraft Toko Table 3. Recommended Inductors for 3A Buck Regulators PART NUMBER L (µH) MAX IDC (A) MAX DCR (mΩ) MANUFACTURER XAL4020-102ME 1.0 8.7 14.6 4 × 4 × 2.1 FDV0530-1R0M 1 8.4 11.2 6.2 × 5.8 × 3 XAL5030-222ME 2.2 9.2 14.5 5.28 × 5.48 × 3.1 IHLP2525CZER2R2M-01 2.2 8 20 6.86 × 6.47 × 3 Vishay 74437346022 2.2 6.5 20 7.3 × 6.6 × 2.8 Wurth Elektonik XAL5030-332ME 3.3 8.7 23.3 5.28 × 5.48 × 3.1 SPM6530T-3R3M 3.3 7.3 27 7.1 × 6.5 × 3 CoilCraft Toko CoilCraft CoilCraft TDK Table 4. Recommended Inductors for 4A Buck Regulators PART NUMBER XAL5030-122ME SPM6530T-1R0M120 XAL5030-222ME L (µH) MAX IDC (A) MAX DCR (mΩ) SIZE IN mm (L × W × H) 1.2 12.5 9.4 5.28 × 5.48 × 3.1 1 14.1 7.81 7.1 × 6.5 × 3 2.2 9.2 14.5 5.28 × 5.48 × 3.1 SPM6530T-2R2M 2.2 8.4 19 7.1 × 6.5 × 3 IHLP2525EZER2R2M-01 2.2 13.6 20.9 6.86 × 6.47 × 5 XAL6030-332ME 3.3 8 20.81 6.36 × 6.56 × 3.1 FDVE1040-3R3M 3.3 9.8 10.1 11.2 × 10 × 4 MANUFACTURER CoilCraft TDK CoilCraft TDK Vishay CoilCraft Toko 3374f 18 For more information www.linear.com/LTC3374 LTC3374 APPLICATIONS INFORMATION 2.All the input supply pins should each have a decoupling capacitor. 3.The connections to the switching regulator input supply pins and their respective decoupling capacitors should be kept as short as possible. The GND side of these capacitors should connect directly to the ground plane of the part. These capacitors provide the AC current to the internal power MOSFETs and their drivers. It is important to minimize inductance from these capacitors to the VIN pins of the LTC3374. 4.The switching power traces connecting SW1, SW2, SW3, SW4, SW5, SW6, SW7, and SW8 to their respective inductors should be minimized to reduce radiated EMI 3.3V TO 5.5V 10µF 3.3V 1A 2.2µH 22µF and parasitic coupling. Due to the large voltage swing of the switching nodes, high input impedance sensitive nodes, such as the feedback nodes, should be kept far away or shielded from the switching nodes or poor performance could result. 5.The GND side of the switching regulator output capacitors should connect directly to the thermal ground plane of the part. Minimize the trace length from the output capacitor to the inductor(s)/pin(s). 6.In a combined buck regulator application the trace length of switch nodes to the inductor must be kept equal to ensure proper operation. VIN1 VIN8 SW1 SW8 FB1 FB8 1.02M 806k 324k 3.0V TO 5.5V 10µF 3.0V 1A 2.2µH 22µF 2.25V TO 5.5V 2.2µH 22µF 1.8V 1A 10µF 1.5V 1A 10µF 1.2V 1A 10µF 1.0V 1A 10µF 649k VIN2 VIN7 SW2 SW7 FB2 FB7 2.25V TO 5.5V 2.2µH 1.0M 715k 365k 22µF 806k LTC3374 2.5V TO 5.5V 10µF 2.5V 1A 2.2µH 22µF VIN3 VIN6 SW3 SW6 FB3 FB6 1.02M 232k 475k 2.25V TO 5.5V 10µF 2.0V 1A 2.2µH 22µF VIN4 VIN5 SW4 SW5 FB4 FB5 2.25V TO 5.5V 2.2µH 255k 665k 22µF 1.02M EN1 EN2 EN3 EN4 EN5 EN6 EN7 EN8 SYNC MODE RT 402k 22µF 464k 1.0M MICROPROCESSOR CONTROL 2.25V TO 5.5V 2.2µH VCC 2.7V TO 5.5V 10µF PGOOD_ALL TEMP EXPOSED PAD MICROPROCESSOR CONTROL 3374 F03 Figure 3. Detailed Front Page Application For more information www.linear.com/LTC3374 3374f 19 LTC3374 APPLICATIONS INFORMATION VIN 5.5V TO 36V CIN 22µF 100k INTVCC VIN INTVCC 2.2µF PGOOD PLLIN/MODE LTC2955TS8-1 VIN EN KILL INT PB MICROPROCESSOR CONTROL ILIM PGND 470pF FREQ 34.8k 0.1µF 1M ITH SENSE+ – TRACK/SS SENSE EXTVCC SGND VFB 22µF 2.5V 1A 22µF 5V 6A 100k MTOP, MBOT: Si7850DP L1 COILCRAFT SER1360-802KL COUT: SANYO 10TPE330M D1: DFLS1100 19.1k VIN8 SW1 SW8 FB1 FB8 10µF 2.2µH 324k 2.2µH COUT 330µF 1nF 324k 649k 10µF RSENSE 7mΩ MBOT BG VIN1 2.2µH L1 8µH SW SGND 10µF MTOP 0.1µF LTC3891 RUN BOOST TMR GND ON 1.2V 1A D1 TG 22µF 1.2V 1A 649k VIN2 VIN7 SW2 SW7 10µF 2.2µH 665k 665k FB2 2.5V 1A 22µF FB7 309k 309k LTC3374 10µF 1.8V 1A 2.2µH 22µF VIN3 VIN6 SW3 SW6 10µF 2.2µH 590k 590k FB3 FB6 475k 1.6V 1A 475k VIN4 10µF 2.2µH 22µF VIN5 SW4 SW5 10µF 2.2µH 511k 511k FB4 511k MODE SYNC EN1 EN2 EN3 EN4 EN5 EN6 EN7 EN8 RT 402k 1.6V 1A 22µF FB5 511k MICROPROCESSOR CONTROL 1.8V 1A 22µF VCC PGOOD_ALL TEMP 10µF MICROPROCESSOR CONTROL EXPOSED PAD 3374 F04 Figure 4. Buck Regulators with Sequenced Start-Up Driven from a High Voltage Upstream Buck Converter 3374f 20 For more information www.linear.com/LTC3374 LTC3374 APPLICATIONS INFORMATION 2.7V TO 5.5V 10µF 2.5V 4A 2.2µH 100µF 665k VIN1 VIN6 SW1 SW2 SW3 SW4 FB1 SW8 SW7 SW6 2.2µH 10µF FB6 309k 10µF 68µF 324k 1.2V 3A 649k VIN2 VIN7 FB2 FB7 10µF LTC3374 10µF 10µF VIN3 VIN8 FB3 FB8 VIN4 VIN5 SW5 10µF 2.2µH 511k FB4 EN1 EN5 EN6 SYNC MODE 10µF FB5 511k EN2 EN3 EN4 EN7 EN8 MICROPROCESSOR CONTROL 22µF 1.6V 1A VCC PGOOD_ALL TEMP 10µF MICROPROCESSOR CONTROL RT 402k EXPOSED PAD 3374 F05 Figure 5. Combined Buck Regulators with Common Input Supply 3374f For more information www.linear.com/LTC3374 21 LTC3374 PACKAGE DESCRIPTION Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. UHF Package 38-Lead Plastic QFN (5mm × 7mm) (Reference LTC DWG # 05-08-1701 Rev C) 0.70 ± 0.05 5.50 ± 0.05 5.15 ± 0.05 4.10 ± 0.05 3.00 REF 3.15 ± 0.05 PACKAGE OUTLINE 0.25 ± 0.05 0.50 BSC 5.5 REF 6.10 ± 0.05 7.50 ± 0.05 RECOMMENDED SOLDER PAD LAYOUT APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 0.75 ± 0.05 5.00 ± 0.10 PIN 1 NOTCH R = 0.30 TYP OR 0.35 × 45° CHAMFER 3.00 REF 37 0.00 – 0.05 38 0.40 ±0.10 PIN 1 TOP MARK (SEE NOTE 6) 1 2 5.15 ± 0.10 5.50 REF 7.00 ± 0.10 3.15 ± 0.10 (UH) QFN REF C 1107 0.200 REF 0.25 ± 0.05 0.50 BSC R = 0.125 TYP R = 0.10 TYP BOTTOM VIEW—EXPOSED PAD NOTE: 1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE M0-220 VARIATION WHKD 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.20mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE 3374f 22 For more information www.linear.com/LTC3374 LTC3374 PACKAGE DESCRIPTION Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. FE Package 38-Lead Plastic TSSOP (4.4mm) (Reference LTC DWG # 05-08-1772 Rev C) Exposed Pad Variation AA 4.75 REF 38 9.60 – 9.80* (.378 – .386) 4.75 REF (.187) 20 6.60 ±0.10 4.50 REF 2.74 REF SEE NOTE 4 6.40 2.74 REF (.252) (.108) BSC 0.315 ±0.05 1.05 ±0.10 0.50 BSC RECOMMENDED SOLDER PAD LAYOUT 4.30 – 4.50* (.169 – .177) 0.50 – 0.75 (.020 – .030) 0.09 – 0.20 (.0035 – .0079) NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS 2. DIMENSIONS ARE IN MILLIMETERS (INCHES) 3. DRAWING NOT TO SCALE 1 0.25 REF 19 1.20 (.047) MAX 0° – 8° 0.50 (.0196) BSC 0.17 – 0.27 (.0067 – .0106) TYP 0.05 – 0.15 (.002 – .006) FE38 (AA) TSSOP REV C 0910 4. RECOMMENDED MINIMUM PCB METAL SIZE FOR EXPOSED PAD ATTACHMENT *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.150mm (.006") PER SIDE 3374f Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. For more information www.linear.com/LTC3374 23 LTC3374 TYPICAL APPLICATION Combined Bucks with 3MHz Switch Frequency and Sequenced Power Up 2.25V TO 5.5V 10µF 10µF 10µF 2V 3A 1µH 68µF 649k VIN1 VIN8 FB8 VIN2 FB2 VIN7 VIN3 FB3 SW7 SW8 SW1 SW2 SW3 FB7 1.2V 1A VIN6 FB6 VIN4 10µF 1µH SW5 SW6 SW4 FB4 1.02M 2.5V 2A 475k VCC PGOOD_ALL MICROPROCESSOR CONTROL 47µF FB5 649k 10µF 3.3V 2A 2.5V TO 5.5V 10µF VIN5 324k 2.7V TO 5.5V 47µF LTC3374 1µH 22µF 1.02M 324k 432k 10µF 10µF 1µH FB1 2.25V TO 5.5V 3.3V TO 5.5V 10µF TEMP SYNC MODE EN1 EN4 EN5 EN7 RT 267k EXPOSED PAD EN2 EN3 EN6 EN8 3374 TA02 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC3589 8-Output Regulator with Sequencing and I2C Triple I2C Adjustable High Efficiency Step-Down DC/DC Converters: 1.6A, 1A, 1A. High Efficiency 1.2A Buck-Boost DC/DC Converter, Triple 250mA LDO Regulators. Pushbutton On/Off Control with System Reset, Flexible Pin-Strap Sequencing Operation. I2C and Independent Enable Control Pins, Dynamic Voltage Scaling and Slew Rate Control. Selectable 2.25MHz or 1.12MHz Switching Frequency, 8µA Standby Current, 40-Pin 6mm × 6mm × 0.75mm QFN. LTC3675 7-Channel Configurable High Power PMIC Four Monolithic Synchronous Buck DC/DCs (1A/1A/500mA/500mA). Buck DC/DCs Can Be Paralleled to Deliver Up to 2× Current with a Single Inductor. Independent 1A Boost and 1A Buck-Boost DC/DCs, Dual String I2C Controlled 40V LED Driver. I2C Programmable Output Voltage, Operating Mode, and Switch Node Slew Rate for All DC/DCs. I2C Read Back of DC/DC, LED Driver, Fault Status, Pushbutton On/Off/Reset, Always-On 25mA LDO. Low Quiescent Current: 16µA (All DC/DCs Off), 4mm × 7mm × 0.75mm 44-Lead QFN Package. LTC3375 8-Channel Programmable Configurable 1A DC/DC 8 × 1A Synchronous Buck Regulators. Can Connect Up to Four Power Stages in Parallel to Make a Single Inductor, High Current Output (4A Maximum), 15 Output Configurations Possible, 7mm × 7mm QFN-48 Package 3374f 24 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 For more information www.linear.com/LTC3374 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com/LTC3374 LT 0513 • PRINTED IN USA LINEAR TECHNOLOGY CORPORATION 2013