LTC3374 8-Channel Parallelable 1A Buck DC/DCs FEATURES DESCRIPTION n 8-Channel Independent Step-Down DC/DCs The LTC®3374 is a high efficiency multioutput power sup- n Master-Slave Configurable for Up to 4A per Output ply IC. The DC/DCs consist of eight synchronous buck Rail with a Single Inductor converters (1A each) all powered from independent 2.25V n Independent V Supplies for Each DC/DC to 5.5V input supplies. IN (2.25V to 5.5V) The DC/DCs may be used independently or in parallel to n All DC/DCs Have 0.8V to V Output Range IN achieve higher currents of up to 4A per output with a shared n Precision Enable Pin Thresholds for Autonomous inductor. The common buck switching frequency may be Sequencing programmed with an external resistor, synchronized to an n 1MHz to 3MHz Programmable/Synchronizable external oscillator, or set to a default internal 2MHz clock. Oscillator Frequency (2MHz Default) The operating mode for all DC/DCs may be programmed n Die Temperature Monitor Output via the MODE pin. n Thermally-Enhanced 38-Lead QFN (5mm × 7mm) and TSSOP Packages To reduce input noise the buck converters are phased in 90° steps. Precision enable pin thresholds provide reli- APPLICATIONS able power-up sequencing. The LTC3374 is available in a compact 38-lead 5mm × 7mm QFN package as well as a n General Purpose Multichannel Power Supplies 38-lead TSSOP package. n Industrial/Automotive/Communications 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 2.7V TO 5.5V VCC BUVCIKN11 2.2µH 0 U.8PV T TOO 1 VAIN1 Buck Efficiency vs I 22µF LOAD 100 MASTER LTC3374 90 BUVCIKN22 2.2µH SLAVE 0.8V TO VIN2 80 UP TO 1A 70 22µF %) Y ( 60 C EN1 EN 50 EN2 MASTER CI 1A BUCK EN3 • FFI 40 2A BUCK EN4 •• E 30 3A BUCK EENN56 BUVCIKN77 2.2µH SLAVE 0U.P8 VT OT O1 AVIN7 20 FORCED CONTINUOU4SA MBUOCDKE EN7 10µF 10 VIN = 3.3V, VOUT = 1.8V EN8 fOSC = 1MHz, L = 3.3µH PGOOD_ALL MASTER 0 TEMP 0 1000 2000 3000 4000 MODE LOAD CURRENT (mA) BUVCIKN88 2.2µH SLAVE 0.8V TO VIN8 3374 TA01b UP TO 1A 10µF SYNC RT 3374 TA01a 3374fc 1 For more information www.linear.com/LTC3374

LTC3374 TABLE OF CONTENTS Features ..................................................... 1 Applications Information ................................17 Applications ................................................ 1 Buck Switching Regulator Output Voltage Typical Application ........................................ 1 and Feedback Network ............................................17 Description.................................................. 1 Buck Regulators .....................................................17 Absolute Maximum Ratings .............................. 3 Combined Buck Regulators.....................................17 Pin Configuration .......................................... 3 Input and Output Decoupling Capacitor Selection...17 Order Information .......................................... 3 PCB Considerations ................................................19 Electrical Characteristics ................................. 4 Package Description .....................................23 Typical Performance Characteristics ................... 6 Revision History ..........................................25 Pin Functions ..............................................11 Typical Application .......................................26 Block Diagram .............................................13 Related Parts ..............................................26 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 3374fc 2 For more information www.linear.com/LTC3374

LTC3374 ABSOLUTE MAXIMUM RATINGS (Note 1) V , FB1-8, EN1-8, V , PGOOD_ALL, Operating Junction Temperature Range IN1-8 CC SYNC, RT, MODE .........................................–0.3V to 6V (Notes 2, 3) ............................................–40°C to 150°C TEMP ..................–0.3V to Lesser of (V + 0.3V) or 6V Storage Temperature Range ..................–65°C to 150°C CC I ...............................................................5mA PGOOD_ALL PIN CONFIGURATION TOP VIEW TOP VIEW TEMP 1 38 VCC EN1 EN2 TEMP VCC MODE EN7 EN8 EN2 2 37 MODE 38 37 36 35 34 33 32 EN1 3 36 EN7 FB1 1 31 FB8 FB1 4 35 EN8 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 39 26 FB7 FB2 9 30 VIN7 FB3 7 GND 25 FB6 FB3 10 39 29 FB7 VIN3 8 24 VIN6 VIN3 11 GND 28 FB6 SW3 9 23 SW6 SW3 12 27 VIN6 SW4 10 22 SW5 SW4 13 26 SW6 VIN4 11 21 VIN5 FB4 12 20 FB5 VIN4 14 25 SW5 13 14 15 16 17 18 19 FB4 15 24 VIN5 4 3 L C T 6 5 EN4 16 23 FB5 N N L N R N N E E D_A SY E E EN3 17 22 EN5 O O PGOOD_ALL 18 21 EN6 G P SYNC 19 20 RT UHF PACKAGE 38-LEAD (5mm × 7mm) PLASTIC QFN FE PACKAGE EXPOSED PAD (PTIJNM A3X9 )= I 1S5 G0N°CD,, θMJAU =S T3 4B°EC S/WOL DERED TO PCB 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 LTC3374FE 38-Lead Plastic TSSOP –40°C to 125°C LTC3374IFE #PBF LTC3374IFE#TRPBF LTC3374FE 38-Lead Plastic TSSOP –40°C to 125°C LTC3374HFE #PBF LTC3374HFE#TRPBF LTC3374FE 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. 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/. Some packages are available in 500 unit reels through designated sales channels with #TRMPBF suffix. 3374fc 3 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 T = 25°C (Note 2). V = V = 3.3V, unless otherwise specified. A CC IN1-8 SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS V V Voltage Range l 2.7 5.5 V VCC CC V Undervoltage Threshold on V V Voltage Falling l 2.35 2.45 2.55 V VCC_UVLO CC CC V Voltage Rising l 2.45 2.55 2.65 V CC I V Input Supply Current All Switching Regulators in Shutdown 8 18 µA VCC_ALLOFF CC I V Input Supply Current At Least 1 Buck Active VCC CC SYNC = 0V, R = 400k, V = 0.85V 45 75 µA T FB_BUCK SYNC = 2MHz 200 275 µA f Internal Oscillator Frequency V = V , SYNC = 0V 1.8 2 2.2 MHz OSC RT CC V = V , SYNC = 0V l 1.75 2 2.25 MHz RT CC R = 400k, SYNC = 0V l 1.8 2 2.2 MHz RT f Synchronization Frequency t , t > 40ns 1 3 MHz SYNC LOW HIGH V SYNC Level High l 1.2 V SYNC SYNC Level Low l 0.4 V V RT Servo Voltage R = 400k l 780 800 820 mV RT RT Temperature Monitor V TEMP Voltage at 25°C 150 mV TEMP(ROOM) ∆V /°C V Slope 6.75 mV/°C TEMP TEMP OT Overtemperature Shutdown Temperature Rising 165 °C OT Hyst Overtemperature Hysteresis 10 °C 1A Buck Regulators V Buck Input Voltage Range l 2.25 5.5 V BUCK V Buck Output Voltage Range V V V OUT FB IN V Undervoltage Threshold on V V Voltage Falling l 1.95 2.05 2.15 V IN_UVLO IN IN V Voltage Rising l 2.05 2.15 2.25 V IN I Burst Mode® Operation V = 0.85V (Note 4) 18 50 µA VIN_BUCK FB_BUCK Forced Continuous Mode Operation I = 0µA, V = 0V 400 550 µA SW_BUCK FB_BUCK Shutdown Input Current All Switching Regulators in Shutdown 0 1 µA Shutdown Input Current At Least One Other Buck Active 1 2 µA I PMOS Current Limit (Note 5) 2.0 2.3 2.7 A FWD V Feedback Regulation Voltage l 780 800 820 mV FB I Feedback Leakage Current V = 0.85V –50 50 nA FB FB_BUCK DMAX Maximum Duty Cycle V = 0V l 100 % FB_BUCK R PMOS On-Resistance I = 100mA 300 mΩ PMOS SW_BUCK R NMOS On-Resistance I = 100mA 300 mΩ NMOS SW_BUCK I PMOS Leakage Current EN_BUCK = 0 –2 2 µA LEAKP I NMOS Leakage Current EN_BUCK = 0 –2 2 µA LEAKN t Soft-Start Time (Note 6) l 0.25 1 3 ms SS V Falling PGOOD Threshold Voltage % of Regulated V 92.5 % PGOOD(FALL) FB V PGOOD Hysteresis % of Regulated V 1 % PGOOD(HYS) FB Buck Regulators Combined I PMOS Current Limit 2 Buck Converters Combined (Note 5) 4.6 A FWD2 I PMOS Current Limit 3 Buck Converters Combined (Note 5) 6.9 A FWD3 I PMOS Current Limit 4 Buck Converters Combined (Note 5) 9.2 A FWD4 3374fc 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 T = 25°C (Note 2). V = V = 3.3V, unless otherwise specified. A CC IN1-8 SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Interface Logic Pins (PGOOD_ALL, MODE) I Output High Leakage Current PGOOD_ALL 5.5V at Pin –1 1 µA OH V Output Low Voltage PGOOD_ALL 3mA into Pin 0.1 0.4 V OL V Input High Threshold MODE l 1.2 V IH V Input Low Threshold MODE l 0.4 V IL Interface Logic Pins (EN1, EN2, EN3, EN4, EN5, EN6, EN7, EN8) V Enable Rising Threshold All Regulators Disabled l 400 730 1200 mV HI_ALLOFF V Enable Falling Hysteresis 60 mV EN_HYS V Enable Rising Threshold At Least One Regulator Enabled l 380 400 420 mV HI I Enable Pin Leakage Current EN = V = V = 5.5V –1 1 µA EN CC IN Note 1: Stresses beyond those listed under Absolute Maximum Ratings Note 3: The LTC3374 includes overtemperature protection which protects may cause permanent damage to the device. Exposure to any Absolute the device during momentary overload conditions. Junction temperatures Maximum Rating condition for extended periods may affect device will exceed 150°C when overtemperature protection is active. Continuous reliability and lifetime. operation above the specified maximum operating junction temperature Note 2: The LTC3374 is tested under pulsed load conditions such that may impair device reliability. T ≈ T . The LTC3374E is guaranteed to meet specifications from Note 4: Static current, switches not switching. Actual current may be J A 0°C to 85°C junction temperature. Specifications over the –40°C to higher due to gate charge losses at the switching frequency. 125°C operating junction temperature range are assured by design, Note 5: The current limit features of this part are intended to protect the characterization and correlation with statistical process controls. The IC from short term or intermittent fault conditions. Continuous operation LTC3374I is guaranteed over the –40°C to 125°C operating junction above the maximum specified pin current rating may result in device temperature range and the LTC3374H is guaranteed over the –40°C to degradation over time. 150°C operating junction temperature range. High junction temperatures Note 6: The soft-start is the time from the first top switch turn on, after an degrade operating lifetimes; operating lifetime is derated for junction enable rising, until the feedback has reached 90% of its nominal regulation temperatures greater than 125°C. Note that the maximum ambient voltage. 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 (T in °C) is calculated from ambient temperature (T in °C) J A and power dissipation (P in Watts) according to the formula: D T = T + (P • θ ) J A D JA where θ (in °C/W) is the package thermal impedance. JA 3374fc 5 For more information www.linear.com/LTC3374

LTC3374 TYPICAL PERFORMANCE CHARACTERISTICS V Undervoltage Threshold Buck V Undervoltage Threshold V Supply Current CC IN CC vs Temperature vs Temperature vs Temperature 2.70 2.30 60 ALL REGULATORS 55 2.65 2.25 IN SHUTDOWN 50 2.60 2.20 45 D (V)2.55 VCC RISING D (V)2.15 VIN RISING µA) 40 UV THRESHOL22..5405 VCC FALLING UV THRESHOL22..1005 VIN FALLING I (VCC_ALLOFF 32235500 2.40 2.00 15 VCC = 3.3V VCC = 5.5V 10 2.35 1.95 5 VCC = 2.7V 2.30 1.90 0 –50 –25 0 25 50 75 100 125 150 –50 –25 0 25 50 75 100 125 150 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) TEMPERATURE (°C) TEMPERATURE (°C) 3374 G01 3374 G02 3374 G03 V Supply Current V Supply Current RT Programmed Oscillator CC CC vs Temperature vs Temperature Frequency vs Temperature 125 400 2.20 AT LEAST ONE BUCK ENABLED AT LEAST ONE BUCK ENABLED RRT = 402k SYNC = 0V 360 SYNC = 2MHz 2.15 FB = 850mV 100 320 2.10 280 VCC = 5.5V I (µA)VCC 7550 VCC = 3.3V VCC = 5.5V I (µA)VCC221406000 VVCCCC == 32..37VV f (MHz)OSC122...900505 VCC = 2.7V 120 1.90 25 80 VCC = 5.5V 40 1.85 VCC = 3.3V VCC = 2.7V 0 0 1.80 –50 –25 0 25 50 75 100 125 150 –50 –25 0 25 50 75 100 125 150 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) TEMPERATURE (°C) TEMPERATURE (°C) 3374 G04 3374 G05 3374 G06 Default Oscillator Frequency vs Temperature Oscillator Frequency vs V CC 2.20 2.20 VRT = VCC 2.15 2.15 2.10 2.10 Hz)2.05 Hz)2.05 VRT = VCC M M (SC2.00 (SC2.00 RRT = 402k O O f1.95 f1.95 1.90 1.90 VCC = 5.5V 1.85 VCC = 3.3V 1.85 VCC = 2.7V 1.80 1.80 –50 –25 0 25 50 75 100 125 150 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 TEMPERATURE (°C) VCC (V) 3374 G07 3374 G08 3374fc 6 For more information www.linear.com/LTC3374

LTC3374 TYPICAL PERFORMANCE CHARACTERISTICS Oscillator Frequency vs R V vs Temperature Enable Threshold vs Temperature T TEMP 4.0 1400 900 VCC = 3.3V ALL REGULATORS DISABLED 3.5 1200 850 VCC = 3.3V 800 3.0 1000 V) 750 m EN RISING Hz) 2.5 mV) 800 LD ( 700 f (MOSC 12..50 V (TEMP 640000 ACTUAL VTEMP THRESHO 660500 EN FALLING N 550 1.0 200 E 500 0.5 0 IDEAL VTEMP 450 0 –200 400 250300350400450500550600650700750800 0 20 40 60 80 100 120 140 –50 –25 0 25 50 75 100 125 150 RRT (kΩ) TEMPERATURE (°C) TEMPERATURE (°C) 3374 G09 3374 G10 3374 G11 Enable Pin Precision Threshold Buck V Supply Current Buck V Supply Current IN IN vs Temperature vs Temperature vs Temperature 420 50 550 Burst Mode OPERATION FORCED CONTINUOUS MODE FB = 850mV 500 FB = 0V 415 40 A) 450 VIN = 5.5V N THRESHOLD (mV) 344491005005 EENN FRAILSLININGG I (µA)VIN_BURST 2300 VIN = 5.5V VIN = 2.25V (µORCED_CONTINUOUS223340505000000 VVIINN == 23..235VV E 390 10 VIN = 3.3V IVIN_F110500 385 50 380 0 0 –50 –25 0 25 50 75 100 125 150 –50 –25 0 25 50 75 100 125 150 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) TEMPERATURE (°C) TEMPERATURE (°C) 3374 G12 3374 G13 3374 G14 PMOS Current Limit VOUT vs Temperature vs Temperature 1.88 2.6 FORCED CONTINUOUS MODE VIN = 3.3V 1.86 ILOAD = 0mA 2.5 1.84 2.4 1.82 V (V)OUT1.80 VIN = 5.5VVIN = 2.25V I (A)FWD 2.3 1.78 VIN = 3.3V 2.2 1.76 2.1 1.74 1.72 2.0 –50 –25 0 25 50 75 100 125 150 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) TEMPERATURE (°C) 3374 G15 3374 G16 3374fc 7 For more information www.linear.com/LTC3374

LTC3374 TYPICAL PERFORMANCE CHARACTERISTICS 1A Buck Efficiency vs I , LOAD PMOS RDS(ON) vs Temperature NMOS RDS(ON) vs Temperature VOUT = 1.8V 550 550 100 VIN = 2.25V VIN = 2.25V Burst Mode OPERATION 500 VIN = 3.3V 500 VIN = 3.3V 90 VIN = 5.5V VIN = 5.5V 80 450 450 70 R (mΩ)DS(ON) 334050000 R (mΩ)DS(ON) 334050000 FFICIENCY (%) 645000 FCMOOORNDVCTEOEINUDTU =O U1S.8V E 30 fOSC = 2MHz 250 250 L = 2.2µH 20 VIN = 2.25V 200 200 10 VIN = 3.3V VIN = 5.5V 150 150 0 –50 –25 0 25 50 75 100 125 150 –50 –25 0 25 50 75 100 125 150 1 10 100 1000 TEMPERATURE (°C) TEMPERATURE (°C) LOAD CURRENT (mA) 3374 G17 3374 G18 3374 G19 1A Buck Efficiency vs I , 2A Buck Efficiency vs I , 2A Buck Efficiency vs I , LOAD LOAD LOAD V  = 2.5V V  = 1.8V V  = 2.5V OUT OUT OUT 100 100 100 90 90 90 Burst Mode Burst Mode Burst Mode 80 OPERATION 80 OPERATION 80 OPERATION 70 70 70 %) FORCED %) FORCED %) FORCED NCY ( 6500 CMOONDTEINUOUS NCY ( 6500 CMOONDTEINUOUS NCY ( 6500 CMOONDTEINUOUS EFFICIE 4300 VfOOSUCT = = 2 2M.5HVz EFFICIE 4300 VfOOSUCT = = 2 1M.8HVz EFFICIE 4300 VfOOSUCT = = 2 2M.5HVz L = 2.2µH L = 2.2µH L = 2.2µH 20 VIN = 2.7V 20 VIN = 2.25V 20 VIN = 2.7V 10 VIN = 3.3V 10 VIN = 3.3V 10 VIN = 3.3V VIN = 5.5V VIN = 5.5V VIN = 5.5V 0 0 0 1 10 100 1000 1 10 100 1000 1 10 100 1000 LOAD CURRENT (mA) LOAD CURRENT (mA) LOAD CURRENT (mA) 3374 G20 3374 G21 3374 G22 3A Buck Efficiency vs I , 3A Buck Efficiency vs I , LOAD LOAD V  = 1.8V V  = 2.5V OUT OUT 100 100 90 90 80 80 Burst Mode EFFICIENCY (%) 6743500000 OBPuErsRt AMToIOdNe FCMOVfOOOORNSDUCCTET EI= ND= U2 1MO.8UHVSz EFFICIENCY (%) 6743500000 OPERATION FCMOOOVfRONODSCTUECEIT ND= =U 2 O2M.U5HSVz L = 2.2µH L = 2.2µH 20 VIN = 2.25V 20 VIN = 2.7V 10 VIN = 3.3V 10 VIN = 3.3V VIN = 5.5V VIN = 5.5V 0 0 1 10 100 1000 1 10 100 1000 LOAD CURRENT (mA) LOAD CURRENT (mA) 3374 G23 3374 G24 3374fc 8 For more information www.linear.com/LTC3374

LTC3374 TYPICAL PERFORMANCE CHARACTERISTICS 4A Buck Efficiency vs I , 4A Buck Efficiency vs I , 1A Buck Efficiency vs Frequency LOAD LOAD V  = 1.8V V  = 2.5V (Forced Continuous Mode) OUT OUT 100 100 100 90 90 90 VIN = 2.25V VIN = 3.3V 80 80 80 Burst Mode Burst Mode 70 OPERATION 70 OPERATION 70 VIN = 5.5V %) %) %) Y ( 60 Y ( 60 FORCED Y ( 60 C C CONTINUOUS C N 50 FORCED N 50 N 50 E E MODE E CI CONTINUOUS CI CI EFFI 4300 MODE VfOOSUCT = = 2 1M.8HVz EFFI 4300 VfOOSUCT = = 2 2M.5HVz EFFI 4300 L = 2.2µH L = 2.2µH 20 VIN = 2.25V 20 VIN = 2.7V 20 VOUT = 1.8V 10 VIN = 3.3V 10 VIN = 3.3V 10 ILOAD = 100mA VIN = 5.5V VIN = 5.5V L = 3.3µH 0 0 0 1 10 100 1000 1 10 100 1000 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 LOAD CURRENT (mA) LOAD CURRENT (mA) FREQUENCY (MHz) 3374 G25 3374 G26 3374 G27 1A Buck Efficiency vs Frequency 1A Buck Efficiency vs I 1A Buck Regulator Load Regulation LOAD (Forced Continuous Mode) (Across Operating Frequency) (Forced Continuous Mode) 100 100 1.820 ILOAD = 100mA fOSC = 2MHz 90 90 1.816 L = 2.2µH 80 ILOAD = 500mA 80 Burst Mode 1.812 70 ILOAD = 20mA 70 OPERATION FORCED 1.808 VIN = 5.5V %) %) CONTINUOUS EFFICIENCY ( 645000 EFFICIENCY ( 645000 MODE fVVOOISNUC =T = =3 1 .13M.V8HVz V (V)OUT111...788900640 VVIINN == 32..32V5V 30 30 L = 3.3µH 1.792 20 VOUT = 1.8V 20 fLO =S C2 .=2 µ2HMHz 1.788 DROPOUT 10 VIN = 3.3V 10 fOSC = 3MHz 1.784 L = 3.3µH L = 1µH 0 0 1.780 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 1 10 100 1000 1 10 100 1000 FREQUENCY (MHz) LOAD CURRENT (mA) LOAD CURRENT (mA) 3374 G28 3374 G29 3374 G30 4A Buck Regulator Load Regulation 1A Buck Regulator Line Regulation (Forced Continuous Mode) (Forced Continuous Mode) 1.820 1.820 fOSC = 2MHz fOSC = 2MHz 1.816 L = 2.2µH L = 2.2µH 1.815 1.812 1.810 1.808 VIN = 5.5V 1.805 (V)UT11..880004 VIN = 3.3V (V)UT1.800 ILOAD = 100mA VO VO ILOAD = 500mA 1.796 VIN = 2.25V 1.795 1.792 1.790 1.788 DROPOUT 1.785 1.784 1.780 1.780 1 10 100 1000 2.25 2.75 3.25 3.75 4.25 4.75 5.25 LOAD CURRENT (mA) VIN (V) 3374 G31 3374 G32 3374fc 9 For more information www.linear.com/LTC3374

LTC3374 TYPICAL PERFORMANCE CHARACTERISTICS 1A Buck Regulator No-Load 4A Buck Regulator No-Load Start-Up Transient (Burst Mode Start-Up Transient (Forced 1A Buck Regulator, Transient Operation) Continuous Mode) Response (Burst Mode Operation) VOUT VOUT 100mVV/ODUIVT 500mV/DIV 500mV/DIV AC-COUPLED INDUCTOR INDUCTOR CURRENT INDUCTOR CURRENT 200mA/DIV CURRENT 500mA/DIV 0mA 500mA/DIV EN 2V/DIV EN 2V/DIV VIN = 3.3V 200µs/DIV 3374 G33 VIN = 3.3V 200µs/DIV 3374 G34 50µs/DIV 3374 G35 LOAD STEP = 100mA TO 700mA VIN = 3.3V VOUT = 1.8V 1A Buck Regulator, Transient 4A Buck Regulator, Transient Response (Forced Continuous 4A Buck Regulator, Transient Response (Forced Continuous Mode) Response (Burst Mode Operation) Mode) VOUT AC1-0C0OmUVP/LDEIDV 100mVV/ODUIVT 100mVV/ODUIVT AC-COUPLED AC-COUPLED INDUCTOR CURRENT INDUCTOR INDUCTOR 200mA/DIV CURRENT CURRENT 1A/DIV 1A/DIV 0mA 0mA 0mA 50µs/DIV 3374 G36 50µs/DIV 3374 G37 50µs/DIV 3374 G38 LOAD STEP = 100mA TO 700mA LOAD STEP = 400mA TO 2.8A LOAD STEP = 400mA TO 2.8A VIN = 3.3V VIN = 3.3V VIN = 3.3V VOUT = 1.8V VOUT = 1.8V VOUT = 1.8V 3374fc 10 For more information www.linear.com/LTC3374

LTC3374 PIN FUNCTIONS (QFN/TSSOP) FB1 (Pin 1/Pin 4): Buck Regulator 1 Feedback Pin. Receives FB4 (Pin 12/Pin 15): Buck Regulator 4 Feedback Pin. feedback by a resistor divider connected across the output. Receives feedback by a resistor divider connected across the output. Connecting FB4 to V combines buck regula- V (Pin 2/Pin 5): Buck Regulator 1 Input Supply. Bypass IN4 IN1 tor 4 with buck regulator 3 for higher current. Up to four to GND with a 10µF or larger ceramic capacitor. converters may be combined in this way. SW1 (Pin 3/Pin 6): Buck Regulator 1 Switch Node. External EN4 (Pin 13/Pin 16): Buck Regulator 4 Enable Input. inductor connects to this pin. Active high. SW2 (Pin 4/Pin 7): Buck Regulator 2 Switch Node. External EN3 (Pin 14/Pin 17): Buck Regulator 3 Enable Input. inductor connects to this pin. Active high. V (Pin 5/Pin 8): Buck Regulator 2 Input Supply. Bypass IN2 PGOOD_ALL (Pin 15/Pin 18): PGOOD Status Pin. Open- to GND with a 10µF or larger ceramic capacitor. May be drain output. When the regulated output voltage of any driven by an independent supply or must be shorted to V IN1 enabled switching regulator is more than 7.5% below its when buck regulator 2 is combined with buck regulator 1 programmed level, this pin is driven LOW. When all buck for higher current. regulators are disabled PGOOD_ALL is driven LOW. FB2 (Pin 6/Pin 9): Buck Regulator 2 Feedback Pin. Receives SYNC (Pin 16/Pin 19): Oscillator Synchronization Pin. Driv- feedback by a resistor divider connected across the output. ing SYNC with an external clock signal will synchronize all Connecting FB2 to V combines buck regulator 2 with IN2 switchers to the applied frequency. The slope compensation buck regulator 1 for higher current. Up to four converters is automatically adapted to the external clock frequency. may be combined in this way. The absence of an external clock signal will enable the FB3 (Pin 7/Pin 10): Buck Regulator 3 Feedback Pin. frequency programmed by the RT pin. SYNC should be Receives feedback by a resistor divider connected across held at ground if not used. Do not float. the output. Connecting FB3 to V combines buck regula- IN3 RT (Pin 17/Pin 20): Oscillator Frequency Pin. This pin tor 3 with buck regulator 2 for higher current. Up to four provides two modes of setting the switching frequency. converters may be combined in this way. Connecting a resistor from RT to ground will set the switch- VIN3 (Pin 8/Pin 11): Buck Regulator 3 Input Supply. Bypass ing frequency based on the resistor value. If RT is tied to to GND with a 10µF or larger ceramic capacitor. May be V the internal 2MHz oscillator will be used. Do not float. CC driven by an independent supply or must be shorted to V IN2 EN6 (Pin 18/Pin 21): Buck Regulator 6 Enable Input. when buck regulator 3 is combined with buck regulator 2 Active high. for higher current. EN5 (Pin 19/Pin 22): Buck Regulator 5 Enable Input. SW3 (Pin 9/Pin 12): Buck Regulator 3 Switch Node. Active high. External inductor connects to this pin. FB5 (Pin 20/Pin 23): Buck Regulator 5 Feedback Pin. SW4 (Pin 10/Pin 13): Buck Regulator 4 Switch Node. Receives feedback by a resistor divider connected across External inductor connects to this pin. the output. Connecting FB5 to V combines buck regula- IN5 VIN4 (Pin 11/Pin 14): Buck Regulator 4 Input Supply. tor 5 with buck regulator 4 for higher current. Up to four Bypass to GND with a 10µF or larger ceramic capacitor. converters may be combined in this way. May be driven by an independent supply or must be shorted to V when buck regulator 4 is combined with IN3 buck regulator 3 for higher current. 3374fc 11 For more information www.linear.com/LTC3374

LTC3374 PIN FUNCTIONS (QFN/TSSOP) V (Pin 21/Pin 24): Buck Regulator 5 Input Supply. V (Pin 30/Pin 33): Buck Regulator 8 Input Supply. IN5 IN8 Bypass to GND with a 10µF or larger ceramic capacitor. Bypass to GND with a 10µF or larger ceramic capacitor. May be driven by an independent supply or must be May be driven by an independent supply or must be shorted to V when buck regulator 5 is combined with shorted to V when buck regulator 8 is combined with IN4 IN7 buck regulator 4 for higher current. buck regulator 7 for higher current. SW5 (Pin 22/Pin 25): Buck Regulator 5 Switch Node. FB8 (Pin 31/Pin 34): Buck Regulator 8 Feedback Pin. External inductor connects to this pin. Receives feedback by a resistor divider connected across the output. Connecting FB8 to V combines buck regula- SW6 (Pin 23/Pin 26): Buck Regulator 6 Switch Node. IN8 tor 8 with buck regulator 7 for higher current. Up to four External inductor connects to this pin. converters may be combined in this way. V (Pin 24/Pin 27): Buck Regulator 6 Input Supply. IN6 EN8 (Pin 32/Pin 35): Buck Regulator 8 Enable Input. Bypass to GND with a 10µF or larger ceramic capacitor. Active high. May be driven by an independent supply or must be shorted to V when buck regulator 6 is combined with EN7 (Pin 33/Pin 36): Buck Regulator 7 Enable Input. IN5 buck regulator 5 for higher current. Active high. FB6 (Pin 25/Pin 28): Buck Regulator 6 Feedback Pin. MODE (Pin 34/Pin 37): Logic Input. MODE enables Burst Receives feedback by a resistor divider connected across Mode functionality for all the buck switching regulators the output. Connecting FB6 to V combines buck regula- when the pin is set low. When the pin is set high, all the IN6 tor 6 with buck regulator 5 for higher current. Up to four buck switching regulators will operate in forced continu- converters may be combined in this way. ous mode. FB7 (Pin 26/Pin 29): Buck Regulator 7 Feedback Pin. V (Pin 35/Pin 38): Internal Bias Supply. Bypass to GND CC Receives feedback by a resistor divider connected across with a 10µF or larger ceramic capacitor. the output. Connecting FB7 to V combines buck regula- IN7 TEMP (Pin 36/Pin 1): Temperature Indication Pin. TEMP tor 7 with buck regulator 6 for higher current. Up to four outputs a voltage of 150mV (typical) at room tempera- converters may be combined in this way. ture. The TEMP voltage will change by 6.75mV/°C (typical) V (Pin 27/Pin 30): Buck Regulator 7 Input Supply. giving an external indication of the LTC3374 internal die IN7 Bypass to GND with a 10µF or larger ceramic capacitor. temperature. May be driven by an independent supply or must be EN2 (Pin 37/Pin 2): Buck Regulator 2 Enable Input. shorted to V when buck regulator 7 is combined with IN6 Active high. buck regulator 6 for higher current. EN1 (Pin 38/Pin 3): Buck Regulator 1 Enable Input. SW7 (Pin 28/Pin 31): Buck Regulator 7 Switch Node. Active high. External inductor connects to this pin. GND (Exposed Pad Pin 39/Exposed Pad Pin 39): Ground. SW8 (Pin 29/Pin 32): Buck Regulator 8 Switch Node. The exposed pad must be connected to a continuous External inductor connects to this pin. ground plane on the printed circuit board directly under the LTC3374 for electrical contact and rated thermal performance. 3374fc 12 For more information www.linear.com/LTC3374

LTC3374 BLOCK DIAGRAM (Pin numbers reflect QFN package) VCC 35 TOP LOGIC 15 PGOOD_ALL SYNC 16 REF, CLK RT 17 8 PGOOD BANDGAP, OSCILLATOR, TEMP 36 UV, OT TEMP MONITOR 34 MODE VIN1 2 30 VIN8 SW1 3 29 SW8 BUCK REGULATOR 1 BUCK REGULATOR 8 FB1 1 1A 1A 31 FB8 EN1 38 32 EN8 MASTER/SLAVE LINES MASTER/SLAVE LINES VIN2 5 27 VIN7 SW2 4 28 SW7 BUCK REGULATOR 2 BUCK REGULATOR 7 FB2 6 1A 1A 26 FB7 EN2 37 33 EN7 MASTER/SLAVE LINES MASTER/SLAVE LINES VIN3 8 24 VIN6 SW3 9 23 SW6 BUCK REGULATOR 3 BUCK REGULATOR 6 FB3 7 1A 1A 25 FB6 EN3 14 18 EN6 MASTER/SLAVE LINES MASTER/SLAVE LINES VIN4 11 21 VIN5 SW4 10 22 SW5 BUCK REGULATOR 4 BUCK REGULATOR 5 FB4 12 1A 1A 20 FB5 EN4 13 19 EN5 MASTER/SLAVE LINES GND (EXPOSED PAD) 39 3374 BD 3374fc 13 For more information www.linear.com/LTC3374

LTC3374 OPERATION Buck Switching Regulators The buck switching regulators are phased in 90° steps to reduce noise and input ripple. The phase step determines The LTC3374 contains eight monolithic 1A synchronous the fixed edge of the switching sequence, which is when buck switching regulators. All of the switching regula- the PMOS turns on. The PMOS off (NMOS on) phase tors are internally compensated and need only external is subject to the duty cycle demanded by the regulator. feedback resistors to set the output voltage. The switch- Bucks 1 and 2 are set to 0°, bucks 3 and 4 are set to 90°, ing regulators offer two operating modes: Burst Mode bucks 5 and 6 are set to 180°, and bucks 7 and 8 are set operation (when the MODE pin is set low) for higher to 270°. In shutdown all SW nodes are high impedance. efficiency at light loads and forced continuous PWM mode The buck regulator enable pins may be tied to V volt- (when the MODE pin is set high) for lower noise at light OUT ages, through a resistor divider, to program power-up loads. The MODE pin collectively sets the operating mode sequencing. for all enabled buck switching regulators. In Burst Mode operation at light loads, the output capacitor is charged Buck Regulators with Combined Power Stages to a voltage slightly higher than its regulation point. The regulator then goes into sleep mode, during which time Up to four adjacent buck regulators may be combined the output capacitor provides the load current. In sleep in a master-slave configuration by connecting their SW most of the regulator’s circuitry is powered down, helping pins together, connecting their VIN pins together, and conserve input power. When the output capacitor droops connecting the higher numbered bucks’ FB pin(s) to the below its programmed value, the circuitry is powered on input supply. The lowest numbered buck is always the and another burst cycle begins. The sleep time decreases master. In Figure 1, buck regulator 1 is the master. The as load current increases. In Burst Mode operation, the feedback network connected to the FB1 pin programs regulator will burst at light loads whereas at higher loads the output voltage to 1.2V. The FB2 pin is tied to VIN1-2, it will operate at constant frequency PWM mode operation. which configures buck regulator 2 as the slave. The SW1 In forced continuous mode, the oscillator runs continu- and SW2 pins must be tied together, as must the VIN1 ously and the buck switch currents are allowed to reverse and VIN2 pins. The slave buck control circuitry draws no under very light load conditions to maintain regulation. current. The enable of the master buck (EN1) controls the This mode allows the buck to run at a fixed frequency with minimal output ripple. VIN L1 VOUT Each buck switching regulator has its own V , SW, FB VIN1 SW1 1.2V and EN pins to maximize flexibility. The enableIN pins have BUCK REGULATOR 1 COUT 2A (MASTER) 400k two different enable threshold voltages that depend on EN1 FB1 the operating state of the LTC3374. With all regulators 800k disabled, the enable pin threshold is set to 730mV (typical). Once any regulator is enabled, the enable pin thresholds VIN of the remaining regulators are set to a bandgap-based VIN2 SW2 400mV and the EN pins are each monitored by a precision comparator. This precision EN threshold may be used to BUCK (RSELGAUVLEA)TOR 2 VIN provide event-based sequencing via feedback from other EN2 FB2 previously enabled regulators. All buck regulators have 3374 F01 forward and reverse-current limiting, soft-start to limit inrush current during start-up, and short-circuit protection. Figure 1. Buck Regulators Configured as Master-Slave 3374fc 14 For more information www.linear.com/LTC3374

LTC3374 OPERATION operation of the combined bucks; the enable of the slave The temperature may be read back by the user by sampling regulator (EN2) must be tied to ground. the TEMP pin analog voltage. The temperature, T, indicated by the TEMP pin voltage is given by: Any combination of 2, 3, or 4 adjacent buck regulators may be combined to provide either 2A, 3A, or 4A of aver- V +19mV T= TEMP •1°C (1) age output load current. For example, buck regulator 1 6.75mV and buck regulator 2 may run independently, while buck regulators 3 and 4 may be combined to provide 2A, while If none of the buck switching regulators are enabled, then buck regulators 5 through 8 may be combined to provide the temperature monitor is shut down to further reduce 4A. Buck regulator 1 is never a slave, and buck regulator quiescent current. 8 is never a master. 15 unique output power stage con- Programming the Operating Frequency figurations are possible to maximize application flexibility. Selection of the operating frequency is a trade-off between Power Failure Reporting Via PGOOD_ALL Pin efficiency and component size. High frequency operation Power failure conditions are reported back via the allows the use of smaller inductor and capacitor values. PGOOD_ALL pin. All buck switching regulators have an Operation at lower frequencies improves efficiency by internal power good (PGOOD) signal. When the regulated reducing internal gate charge losses but requires larger output voltage of an enabled switcher rises above 93.5% inductance values and/or capacitance to maintain low of its programmed value, the PGOOD signal will transition output voltage ripple. high. When the regulated output voltage falls below The operating frequency for all of the LTC3374 regulators 92.5% of its programmed value, the PGOOD signal is is determined by an external resistor that is connected pulled low. If any internal PGOOD signal stays low for between the RT pin and ground. The operating frequency greater than 100µs, then the PGOOD_ALL pin is pulled can be calculated by using the following equation: low, indicating to a microprocessor that a power failure 11 fault has occurred. The 100µs filter time prevents the pin 8•10 •ΩHz f = (2) from being pulled low due to a transient. OSC R T An error condition that pulls the PGOOD_ALL pin low While the LTC3374 is designed to function with operat- is not latched. When the error condition goes away, the ing frequencies between 1MHz and 3MHz, it has safety PGOOD_ALL pin is released and is pulled high if no other clamps that will prevent the oscillator from running faster error condition exists. If no buck switching regulators are than 4MHz (typical) or slower than 250kHz (typical). Tying enabled, then PGOOD_ALL will be pulled low. the RT pin to V sets the oscillator to the default internal CC operating frequency of 2MHz (typical). Temperature Monitoring and Overtemperature Protection The LTC3374’s internal oscillator can be synchronized through an internal PLL circuit, to an external frequency To prevent thermal damage to the LTC3374 and its sur- by applying a square wave clock signal to the SYNC pin. rounding components, the LTC3374 incorporates an During synchronization, the top MOSFET turn-on of buck overtemperature (OT) function. When the LTC3374 die switching regulators 1 and 2 are locked to the rising edge temperature reaches 165°C (typical) all enabled buck of the external frequency source. All other buck switching switching regulators are shut down and remain in shutdown until the die temperature falls to 155°C (typical). 3374fc 15 For more information www.linear.com/LTC3374

LTC3374 OPERATION regulators are locked to the appropriate phase of the ex- When the external clock is removed the LTC3374 needs ternal frequency source (see Buck Switching Regulators). approximately 5µs to detect the absence of the external The synchronization frequency range is 1MHz to 3MHz. clock. During this time, the PLL will continue to provide clock cycles before it recognizes the lack of a SYNC input. After detecting an external clock on the first rising edge of Once the external clock removal has been identified, the the SYNC pin, the PLL starts up at the current frequency oscillator will gradually adjust its operating frequency to being programmed by the RT pin. The internal PLL then match the desired frequency programmed at the RT pin. requires a certain number of periods to gradually settle SYNC should be connected to ground if not used. until the frequency at SW matches the frequency and phase of SYNC. 3374fc 16 For more information www.linear.com/LTC3374

LTC3374 APPLICATIONS INFORMATION Buck Switching Regulator Output Voltage Combined Buck Regulators and Feedback Network A single 2A buck regulator is available by combining two The output voltage of the buck switching regulators is adjacent 1A buck regulators together. Likewise a 3A or 4A programmed by a resistor divider connected from the buck regulator is available by combining any three or four switching regulator’s output to its feedback pin and is adjacent buck regulators respectively. Tables 2, 3, and 4 given by V = V (1 + R2/R1) as shown in Figure 2. show recommended inductors for these configurations. OUT FB Typical values for R1 range from 40k to 1M. The buck The input supply needs to be decoupled with a 22µF capaci- regulator transient response may improve with optional tor while the output needs to be decoupled with a 47µF capacitor C that helps cancel the pole created by the FF capacitor for a 2A combined buck regulator. Likewise for feedback resistors and the input capacitance of the FB 3A and 4A configurations the input and output capacitance pin. Experimentation with capacitor values between 2pF must be scaled up to account for the increased load. Refer and 22pF may improve transient response. to the Capacitor Selection section for details on selecting a proper capacitor. VOUT In many cases, any extra unused buck converters may be + BUCK SWITCHING R2 CFF COUT used to increase the efficiency of the active regulators. REGULATOR In general the efficiency will improve for any regulators FB (OPTIONAL) running close to their rated load currents. If there are R1 unused regulators, the user should look at their specific applications and current requirements to decide whether 3374 F02 to add extra stages. Figure 2. Feedback Components Input and Output Decoupling Capacitor Selection Buck Regulators The LTC3374 has individual input supply pins for each All eight buck regulators are designed to be used with buck switching regulator and a separate V pin that CC inductors ranging from 1µH to 3.3µH depending on the supplies power to all top level control and logic. Each of lowest switching frequency that the buck regulator must these pins must be decoupled with low ESR capacitors operate at. To operate at 1MHz a 3.3µH inductor should to GND. These capacitors must be placed as close to be used, while to operate at 3MHz a 1µH inductor may be the pins as possible. Ceramic dielectric capacitors are a used. Table 1 shows some recommended inductors for good compromise between high dielectric constant and the buck regulators. stability versus temperature and DC bias. Note that the capacitance of a capacitor deteriorates at higher DC bias. The input supply needs to be decoupled with a 10µF It is important to consult manufacturer data sheets and capacitor while the output needs to be decoupled with a obtain the true capacitance of a capacitor at the DC bias 22µF capacitor. Refer to the Capacitor Selection section voltage it will be operated at. For this reason, avoid the for details on selecting a proper capacitor. use of Y5V dielectric capacitors. The X5R/X7R dielectric capacitors offer good overall performance. 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. 3374fc 17 For more information www.linear.com/LTC3374

LTC3374 APPLICATIONS INFORMATION Table 1. Recommended Inductors for 1A Buck Regulators PART NUMBER L (µH) MAX I (A) MAX DCR (mΩ) SIZE IN mm (L × W × H) MANUFACTURER DC IHLP1212ABER1R0M-11 1.0 3 38 3 × 3.6 × 1.2 Vishay 1239AS-H-1R0N 1 2.5 65 2.5 × 2.0 × 1.2 Toko XFL4020-222ME 2.2 3.5 23.5 4 × 4 × 2.1 CoilCraft 1277AS-H-2R2N 2.2 2.6 84 3.2 × 2.5 × 1.2 Toko IHLP1212BZER2R2M-11 2.2 3 46 3 × 3.6 × 1.2 Vishay XFL4020-332ME 3.3 2.8 38.3 4 × 4 × 2.1 CoilCraft IHLP1212BZER3R3M-11 3.3 2.7 61 3 × 3.6 × 1.2 Vishay Table 2. Recommended Inductors for 2A Buck Regulators PART NUMBER L (µH) MAX I (A) MAX DCR (mΩ) SIZE IN mm (L × W × H) MANUFACTURER DC XFL4020-102ME 1.0 5.1 11.9 4 × 4 × 2.1 CoilCraft 74437324010 1 5 27 4.45 × 4.06 × 1.8 Wurth Elektronik XAL4020-222ME 2.2 5.6 38.7 4 × 4 × 2.1 CoilCraft FDV0530-2R2M 2.2 5.3 15.5 6.2 × 5.8 × 3 Toko IHLP2020BZER2R2M-11 2.2 5 37.7 5.49 × 5.18 × 2 Vishay XAL4030-332ME 3.3 5.5 28.6 4 × 4 × 3.1 CoilCraft FDV0530-3R3M 3.3 4.1 34.1 6.2 × 5.8 × 3 Toko Table 3. Recommended Inductors for 3A Buck Regulators PART NUMBER L (µH) MAX I (A) MAX DCR (mΩ) SIZE IN mm (L × W × H) MANUFACTURER DC XAL4020-102ME 1.0 8.7 14.6 4 × 4 × 2.1 CoilCraft FDV0530-1R0M 1 8.4 11.2 6.2 × 5.8 × 3 Toko XAL5030-222ME 2.2 9.2 14.5 5.28 × 5.48 × 3.1 CoilCraft 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 CoilCraft SPM6530T-3R3M 3.3 7.3 27 7.1 × 6.5 × 3 TDK Table 4. Recommended Inductors for 4A Buck Regulators PART NUMBER L (µH) MAX I (A) MAX DCR (mΩ) SIZE IN mm (L × W × H) MANUFACTURER DC XAL5030-122ME 1.2 12.5 9.4 5.28 × 5.48 × 3.1 CoilCraft SPM6530T-1R0M120 1 14.1 7.81 7.1 × 6.5 × 3 TDK XAL5030-222ME 2.2 9.2 14.5 5.28 × 5.48 × 3.1 CoilCraft SPM6530T-2R2M 2.2 8.4 19 7.1 × 6.5 × 3 TDK IHLP2525EZER2R2M-01 2.2 13.6 20.9 6.86 × 6.47 × 5 Vishay XAL6030-332ME 3.3 8 20.81 6.36 × 6.56 × 3.1 CoilCraft FDVE1040-3R3M 3.3 9.8 10.1 11.2 × 10 × 4 Toko 3374fc 18 For more information www.linear.com/LTC3374

LTC3374 APPLICATIONS INFORMATION PCB Considerations 4. The switching power traces connecting SW1, SW2, SW3, SW4, SW5, SW6, SW7, and SW8 to their respective When laying out the printed circuit board, the following inductors should be minimized to reduce radiated EMI list should be followed to ensure proper operation of the and parasitic coupling. Due to the large voltage swing LTC3374: of the switching nodes, high input impedance sensitive 1. The exposed pad of the package (Pin 39) should connect nodes, such as the feedback nodes, should be kept far directly to a large ground plane to minimize thermal and away or shielded from the switching nodes or poor electrical impedance. performance could result. 2. All the input supply pins should each have a decoupling 5. The GND side of the switching regulator output capaci- capacitor. tors should connect directly to the thermal ground plane of the part. Minimize the trace length from the output 3. The connections to the switching regulator input supply capacitor to the inductor(s)/pin(s). pins and their respective decoupling capacitors should be kept as short as possible. The GND side of these 6. In a combined buck regulator application the trace length capacitors should connect directly to the ground plane of switch nodes to the inductor must be kept equal to of the part. These capacitors provide the AC current ensure proper operation. to the internal power MOSFETs and their drivers. It is important to minimize inductance from these capacitors to the V pins of the LTC3374. IN 3374fc 19 For more information www.linear.com/LTC3374

LTC3374 APPLICATIONS INFORMATION 3.3V TO 5.5V VIN1 VIN8 2.25V TO 5.5V 2.2µH 2.2µH 10µF 3.3V SW1 SW8 1.8V 10µF 1A 1A 22µF 1.02M 806k 22µF FB1 FB8 324k 649k 3.0V TO 5.5V VIN2 VIN7 2.25V TO 5.5V 2.2µH 2.2µH 10µF 3.0V SW2 SW7 1.5V 10µF 1A 1A 22µF 1.0M 715k 22µF FB2 FB7 365k 806k LTC3374 2.5V TO 5.5V VIN3 VIN6 2.25V TO 5.5V 2.2µH 2.2µH 10µF 2.5V SW3 SW6 1.2V 10µF 1A 1A 22µF 1.02M 232k 22µF FB3 FB6 475k 464k 2.25V TO 5.5V VIN4 VIN5 2.25V TO 5.5V 2.2µH 2.2µH 10µF 2.0V SW4 SW5 1.0V 10µF 1A 1A 22µF 1.0M 255k 22µF FB4 FB5 665k 1.02M EN1 EN2 VCC 2.7V TO 5.5V EN3 10µF EN4 MICROPROCESSOR EN5 CONTROL EN6 EN7 EN8 SYNC MODE PGOOD_ALL MICROPROCESSOR RT TEMP CONTROL 402k EXPOSED PAD 3374 F03 Figure 3. Detailed Front Page Application 3374fc 20 For more information www.linear.com/LTC3374

LTC3374 APPLICATIONS INFORMATION VIN 5.5V TO 36V CIN 22µF VIN INTVCC 100k 2.2µF INTVCC PGOOD PGND PLLIN/MODE D1 LTC2955TS8-1 ILIM LTC3891 TG 0.1µF MTOP VIN EN RUN BOOST 8Lµ1H R7SmENΩSE MICROPROCOCENSTSROORL KIPNIBLTL 470pF34.8k FREQ SBWG MBOT C33O0UµTF 56VA ITH TMR GND ON SENSE+ 0.1µF 1nF TRACK/SS SENSE– EXTVCC 100k 1M SGND VFB MTOP, MBOT: Si7850DP SGND L1 COILCRAFT SER1360-802KL 19.1k COUT: SANYO 10TPE330M D1: DFLS1100 VIN1 VIN8 10µF 10µF 2.2µH 2.2µH 1.2V SW1 SW8 1.2V 1A 1A 22µF 324k 324k 22µF FB1 FB8 649k 649k VIN2 VIN7 10µF 10µF 2.2µH 2.2µH 2.5V SW2 SW7 2.5V 1A 1A 22µF 665k 665k 22µF FB2 FB7 309k 309k LTC3374 VIN3 VIN6 10µF 10µF 2.2µH 2.2µH 1.8V 1.8V SW3 SW6 1A 1A 22µF 590k 590k 22µF FB3 FB6 475k 475k VIN4 VIN5 10µF 10µF 2.2µH 2.2µH 1.6V SW4 SW5 1.6V 1A 1A 22µF 511k 511k 22µF FB4 FB5 511k 511k MICROPROCESSOR MODE CONTROL SYNC VCC 10µF EN1 EN2 EN3 EN4 EN5 EN6 EN7 EN8 PGOOD_ALL MICROPROCESSOR RT TEMP CONTROL 402k EXPOSED PAD 3374 F04 Figure 4. Buck Regulators with Sequenced Start-Up Driven from a High Voltage Upstream Buck Converter 3374fc 21 For more information www.linear.com/LTC3374

LTC3374 APPLICATIONS INFORMATION 2.7V TO 5.5V VIN1 VIN6 10µF 2.2µH SW1 SW8 2.2µH 10µF 2.5V SW2 SW7 1.2V 4A 100µF 665k SSWW34 SW6 324k 68µF3A FB1 FB6 309k 649k VIN2 VIN7 10µF 10µF FB2 FB7 LTC3374 VIN3 VIN8 10µF 10µF FB3 FB8 VIN4 VIN5 10µF 2.2µH 10µF 1.6V SW5 1A 22µF 511k FB4 FB5 EN2 511k EN3 EN4 EN7 EN8 VCC 10µF EN1 PGOOD_ALL MICROPROCESSOR MICROPROCESSOR EN5 TEMP CONTROL CONTROL EN6 SYNC MODE RT EXPOSED PAD 3374 F05 Figure 5. Combined Buck Regulators with Common Input Supply 3374fc 22 For more information www.linear.com/LTC3374

LTC3374 PACKAGE DESCRIPTION Please refer to http://www.linear.com/product/LTC3374#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 PIN 1 NOTCH R = 0.30 TYP OR 0.75 ± 0.05 3.00 REF 0.35 × 45° CHAMFER 5.00 ± 0.10 0.00 – 0.05 37 38 0.40 ±0.10 PIN 1 TOP MARK 1 (SEE NOTE 6) 2 5.15 ± 0.10 7.00 ± 0.10 5.50 REF 3.15 ± 0.10 (UH) QFN REF C 1107 0.200 REF 0.25 ± 0.05 R = 0.125 R = 0.10 TYP TYP 0.50 BSC BOTTOM VIEW—EXPOSED PAD NOTE: 1. DRAWING CONFORMS TO JEDEC PACKAGE 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE OUTLINE M0-220 VARIATION WHKD MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.20mm ON ANY SIDE 2. DRAWING NOT TO SCALE 5. EXPOSED PAD SHALL BE SOLDER PLATED 3. ALL DIMENSIONS ARE IN MILLIMETERS 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE 3374fc 23 For more information www.linear.com/LTC3374

LTC3374 PACKAGE DESCRIPTION Please refer to http://www.linear.com/product/LTC3374#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 9.60 – 9.80* (.378 – .386) 4.75 REF (.187) 38 20 6.60 ±0.10 2.74 REF 4.50 REF SEE NOTE 4 6.40 2.74 0.315 ±0.05 REF(.252) (.108) BSC 1.05 ±0.10 0.50 BSC RECOMMENDED SOLDER PAD LAYOUT 1 19 1.20 4.30 – 4.50* (.047) (.169 – .177) 0.25 MAX REF 0° – 8° 0.50 0.09 – 0.20 0.50 – 0.75 (.0196) 0.05 – 0.15 (.0035 – .0079) (.020 – .030) BSC (.002 – .006) 0.17 – 0.27 (.0067 – .0106) FE38 (AA) TSSOP REV C 0910 TYP NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS 4. RECOMMENDED MINIMUM PCB METAL SIZE 2. DIMENSIONS ARE INMILLIMETERS FOR EXPOSED PAD ATTACHMENT (INCHES) *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH 3. DRAWING NOT TO SCALE SHALL NOT EXCEED 0.150mm (.006") PER SIDE 3374fc 24 For more information www.linear.com/LTC3374

LTC3374 REVISION HISTORY REV DATE DESCRIPTION PAGE NUMBER A 11/13 Modified Figure 5 – removed a resistor. 22 B 06/15 Modified Typical Application circuit 1 Changed part marking on TSSOP package 3 Changed typical specifications: R and R 4 PMOS NMOS Added conditions for V specifications 4 PGOOD Modified various curves 8, 9 Modified Temperature Monitoring section 15 Modified 2A inductor table 18 Added Related Parts 26 C 10/15 Added Note 6 to t specification 4, 5 SS Modified conditions graphs G27, G28 9 3374fc Information furnished by Linear Technology Corporation is believed to be accurate and reliable. 25 However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa- tion that the interconneFcotior nm oof irtse ciinrcfouirtms aast dioensc wribwedw h.leirneeina rw.cilol nmot/ LinTfCrin3g3e7 o4n existing patent rights.

LTC3374 TYPICAL APPLICATION Combined Bucks with 3MHz Switch Frequency and Sequenced Power Up 2.25V TO 5.5V VIN1 VIN8 3.3V TO 5.5V 10µF FB8 10µF VIN2 VIN7 10µF FB2 10µF 1µH 10µF VFBIN33 SSWW78 1.02M 47µF 32.A3V 1µH SW1 FB7 2V 3A SW2 324k 68µF 649k SW3 LTC3374 FB1 VIN6 2.5V TO 5.5V 432k FB6 10µF 2.25V TO 5.5V VIN4 VIN5 10µF 10µF 1µH 1µH 1.2V 2.5V SW4 SW5 1A 2A 22µF 324k SW6 1.02M 47µF FB4 FB5 649k 475k 2.7V TO 5.5V VCC 10µF PGOOD_ALL RT 267k MICROPROCESSOR TEMP CONTROL SYNC MODE EN1 EN2 EN4 EN3 EN5 EN6 EN7 EN8 EXPOSED PAD 3374 TA02 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC3370/ 4-Channel Configurable DC/DC 4 Synchronous Buck Regulators with 8 × 1A Power Stages. Can Connect Up to Four Power Stages LTC3371 with 8 × 1A Power Stages in Parallel to Make a Single Inductor, High Current Output (4A Maximum), 8 Output Configurations Possible, Precision PGOODALL Indication (LTC3370) or Precision RST Monitoring with Windowed Watchdog Timer (CT Programmable, LTC3371), 38-Lead (5mm × 7mm × 0.75mm) QFN and TSSOP Packages (LTC3371) and 32-Lead (5mm × 5mm × 0.75mm) QFN Package (LTC3371). LTC3589 8-Output Regulator with Triple I2C Adjustable High Efficiency Step-Down DC/DC Converters: 1.6A, 1A, 1A. High Efficiency 1.2A Sequencing and I2C 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 Four Monolithic Synchronous Buck DC/DCs (1A/1A/500mA/500mA). Buck DC/DCs Can Be Paralleled Power PMIC 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 8 × 1A Synchronous Buck Regulators. Can Connect Up to Four Power Stages in Parallel to Make Configurable 1A DC/DC a Single Inductor, High Current Output (4A Maximum), 15 Output Configurations Possible, 7mm × 7mm QFN-48 Package 3374fc 26 Linear Technology Corporation LT 1015 REV C • PRINTED IN USA 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  LINEAR TECHNOLOGY CORPORATION 2013