LTC3126 42V, 2.5A Synchronous Step-Down Regulator with No-Loss Input PowerPath Fea T Descrip T n Seamless, Automatic Transition Between Two Input The LTC 3126 is a high efficiency synchronous buck Power Sources converter with an internal no-loss PowerPath supporting n Wide Input Voltage Range: 2.4V to 42V seamless operation from two separate input power sources. n Wide Output Voltage Range: 0.818V to V Pin-selectable ideal diode-OR and priority input modes IN n Up to 2.5A Continuous Output Current with user programmable undervoltage lockout thresholds n Pin-Selectable Priority and Ideal Diode-OR Modes provide full control over the transition between the input n Burst Mode Operation, I = 2A power sources. The fast, automatic switchover provided Q n 95% Efficiency at 1A, V = 12V, V = 5V by the internal PowerPath eliminates the need for hold-up IN OUT n 1A Current in Shutdown capacitors and minimizes disturbances on the output rail. n Programmable Input UVLO Thresholds An active input channel indicator and independent input n Input Valid, Priority Channel and PGOOD Indicators and output power good signals provide complete feedback n 200kHz to 2.2MHz Fixed Frequency PWM of the power system status. n Synchronizable to an External Clock A wide 2.4V to 42V input voltage range, 2.5A output cur- n Current Mode Control with 60ns Minimum On-Time rent capability and 2A Burst Mode operation quiescent n Minimal External Components current facilitate use of the LTC3126 with a wide variety n Thermally Enhanced 28-Lead 4mm 5mm QFN and of power sources including supercapacitors, automo- 28-Lead TSSOP Packages tive batteries, unregulated wall adapters and single to multicell stacks of most battery chemistries. Additional a T features include 1A current in shutdown, internal soft- start and thermal protection. The LTC3126 is available n Portable Industrial/Communications Test Equipment in thermally enhanced 28-lead 4mm 5mm QFN and n Battery and Supercapacitor Backup Power 28-lead TSSOP packages. n Automotive Power with Battery Backup L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks n Uninterruptible Power Supplies and PowerPath is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Typical a T 2MHz, 3.3V/2.5A Supply from Automotive and Battery Inputs 0.1F 0.1F AUTOMOTIVE Switchover to Battery Power, 2.5A Load BST2 COM2 BST1 COM1 10V TO 24V V 2.2H IN1 V OUT 42V TRANSIENT 15F PV SW 3.3V IN1 V 5V/DIV IN1 EXTV 47F 2.5A CC V + IN2 V 5V/DIV 10pF 1.13M IN2 4.7F BATTERY PV IN2 + AUTOMOTIVE FB 4.2V TO 24V INPUT UNPLUGGED PV CC LTC3126 374k V CC V 200mV/DIV OUT ENA 4.7F V REF INDUCTOR CURRENT 2A/DIV PRIORITY 499k VALID1 V SET1 VALID2 PRIORITY 5V/DIV PGOOD 249k 3126 TA01b V SET2 50s/DIV 249k PWM/SYNC 16.5k DIODE RT GND PGND 3126 TA01a 3126f 1 For more information www.linear.com/LTC3126 ion pplica ions pplica ion uresLTC3126 a T e Maxi Mu M r a T (Note 1) PV , PV , V , V .............................................42V BST2 Pin Above COM2 ...............................................6V IN1 IN2 IN1 IN2 EXTV .....................................................................42V Operating Junction Temperature Range CC V , PV ....................................................................6V (Notes 2, 4) ............................................ 40C to 150C CC CC V , V , V , FB, RT ..........................................6V Storage Temperature.............................. 65C to 150C REF SET1 SET2 PWM/SYNC, DIODE, ENA ...........................................6V Lead Temperature (Soldering, 10 sec) VALID1, VALID2, PGOOD, PRIORITY ............................6V TSSOP ..............................................................300C BST1 Pin Above COM1 ...............................................6V p c F T TOP VIEW TOP VIEW V 1 28 V IN1 IN2 PWM/SYNC 2 27 PV IN1 VALID1 3 26 DIODE 28 27 26 25 24 23 VALID2 4 25 BST1 VALID2 1 22 BST1 V 5 24 COM1 CC V 2 21 COM1 CC PV 6 23 SW PV 3 20 SW CC CC EXTV 7 22 PGND EXTV 4 19 PGND CC 29 CC 29 PGND PGND V 5 18 PGND V 8 21 PGND SET1 SET1 V 6 17 SW V 9 20 SW SET2 SET2 V 7 16 COM2 REF V 10 19 COM2 REF GND 8 15 BST2 GND 11 18 BST2 9 10 11 12 13 14 FB 12 17 ENA RT 13 16 PV IN2 PGOOD 14 15 PRIORITY UFD PACKAGE FE PACKAGE 28-LEAD (4mm 5mm) PLASTIC QFN 28-LEAD PLASTIC TSSOP T = 150C, = 34C/W JMAX JA T = 150C, = 30C/W JMAX JA EXPOSED PAD (PIN 29) IS PGND, MUST BE SOLDERED TO PCB EXPOSED PAD (PIN 29) IS PGND, MUST BE SOLDERED TO PCB