LTC3446 Monolithic Buck Regulator with Dual VLDO Regulators Fea T Descrip T n High Efficiency Triple Step-Down Outputs from a The LTC 3446 combines a synchronous buck DC/DC con- Single Input Supply verter with two very low dropout (VLDO) linear regulators n 1A Synchronous Buck Regulator Provides Main to provide up to three stepped-down output voltages from Step-Down Output and Powers Two 300mA VLDO a single input voltage. The input voltage range is ideally Linear Regulators suited for Li-Ion battery-powered applications, as well n Output Voltages as Low as 400mV (VLDO Outputs) as powering low voltage logic from 5V or 3.3V rails. The n Power Good Output output voltage range extends down to 0.4V for the VLDO n Input Voltage Range: 2.7V to 5.5V regulators and 0.8V for the buck. n Independent Enable Pin for Each Supply The 1A synchronous buck converter provides the main n Low (140A Typ) No-Load Quiescent Current with output with high efficiency, typically 85%. The two 300mA All Outputs Enabled VLDO regulators can run off the main output to provide n Constant Frequency Current Mode Operation two additional lower voltage outputs. A built-in supply n 2.25MHz Switching Frequency Uses Small Inductors monitor provides a power good indication. n Defeatable Automatic Burst Mode Operation for The buck converter switches at 2.25MHz, allowing the use High Efficiency at Light Loads n of small surface mount inductors and capacitors. Constant 1.5% Reference Accuracy n frequency current mode operation produces controlled Overtemperature Protection n output spectrum and fast transient response. A mode- Thermally Enhanced 4mm 3mm 14-Pin DFN select pin allows automatic Burst Mode operation to be Package enabled for higher efficiency at light load, or disabled for lower noise operation down to very light loads. The two a T VLDO regulators are stable with ceramic output capacitors n Low Power Handheld Devices as small as 1F. n Low Voltage and Multivoltage Power for Digital L, LT, LTC, LTM and Burst Mode are registered trademarks and VLDO, Hot Swap, PowerPath and Bat-Track are trademarks of Linear Technology Corporation. All other trademarks are the Logic, I/O, FPGAs, CPLDs, ASICs and CPUs property of their respective owners. Protected by U.S. Patents including 5481178, 6611131, 6304066, 6498466, 6580258. Typical a T L1 1.8H V OUT V IN Buck Efficiency vs Buck Load Current V SW 1.8V IN 2.9V TO 5.5V 22F 22F 400mA MAX 59k 100 X7R X7R PWM BUCKFB Burst Mode MODE OPERATION 47.5k 90 LTC3446 LV IN 80 V OUT PGOOD LV 1.5V OUT1 2.2F MODESEL 300mA MAX DIGITAL 110k 70 X7R ENBUCK CONTROL LV ENLDO1 FB1 ENLDO2 60 40.2k 3.3k V V = 2.7V OUT 50 IN I LV 1.2V TH OUT2 V = 3.6V IN 2.2F 300mA MAX 1000pF V = 4.2V IN 80.6k X7R 40 LV 1 10 100 1000 FB2 LOAD CURRENT (mA) GND 40.2k 3446 TA01 3446 TA01b L1: TOKO A960AW-1R8M 3446ff 1 EFFICIENCY (%) ion pplica ions pplica ion uresLTC3446 a Te Maxi Mu M r a T p in c F T (Note 1) TOP VIEW V , LV to GND ......................................... 0.3V to 6V IN IN MODESEL 1 14 SW MODESEL, ENBUCK, ENLDO1, V 2 13 ENBUCK IN ENLDO2 to GND .......................................... 0.3V to 6V I 3 12 BUCKFB TH BUCKFB to GND .......................................... 0.3V to 6V PGOOD 4 15 11 ENLDO1 LV , LV to GND .................................... 0.3V to 6V LV 5 10 LV FB1 FB2 OUT1 FB1 LV 6 9 LV IN FB2 I to GND ..... 0.3V to the Lesser of (V + 0.3V) or 3V TH IN LV 7 8 ENLDO2 OUT2 SW to GND ......0.3V to the Lesser of (V + 0.3V) or 6V IN LV , LV DE PACKAGE OUT1 OUT2 14-LEAD (4mm 3mm) PLASTIC DFN to GND .......... 0.3V to the Lesser of (LV + 0.3V) or 6V IN T = 125C, = 43C/W JMAX JA EXPOSED PAD (PIN 15) IS GND, MUST BE SOLDERED TO PCB PGOOD to GND ............................................ 0.3V to 6V LV , LV Short-Circuit OUT1 OUT2 to GND Duration ............................................... Indefinite Operating Junction Temperature Range (Note 2) .................................................. 40C to 125C Storage Temperature Range .................. 65C to 150C Der in F Ma T LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC3446EDE PBF LTC3446EDE TRPBF 3446 14-Lead (4mm 3mm) Plastic DFN 40C to 125C LTC3446IDE PBF LTC3446IDE TRPBF 3446 14-Lead (4mm 3mm) Plastic DFN 40C to 125C 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 non-standard lead based finish parts. For more information on lead free part marking, go to: