LTC3523EUD-PBF

LTC3523/LTC3523-2 Synchronous 600mA Step-Up and 400mA Step-Down DC/DC Converters FEATURES n DESCRIPTION The LTC®3523/LTC3523-2 combine a 600mA step-up DC/DC converter with a 400mA synchronous step-down DC/DC converter in a tiny 3mm × 3mm package. The 1.2MHz/2.4MHz switching frequencies minimize the solution footprint while maintaining high efficiency. Both converters feature soft-start and internal compensation, simplifying the design. Both the step-up and step-down converters are current mode controlled and utilize an internal synchronous rectifier for high efficiency. The step-up supports 0% duty cycle operation and the step-down converter supports 100% duty cycle operation to extend battery run time. If the MODE pin is held high, both converters automatically transition between Burst Mode operation and PWM operation improving light load efficiency. Fixed, low noise 1.2MHz/2.4MHz PWM operation is selected when MODE is grounded. The LTC3523/LTC3523-2 provide a sub-3μA shutdown mode, overtemperature shutdown and current limit protection on both converters. The LTC3523/LTC3523-2 are housed in a 16-lead 3mm × 3mm × 0.75mm QFN package. L, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. n n n n n n n n n n Dual High Efficiency DC/DC Converters: Step-Up (VOUT = 1.8V to 5.25V, ISW = 600mA) Step-Down (VOUT = 0.615V to 5.5V, IOUT = 400mA) 1.8V to 5.5V Input Voltage Range Up to 94% Efficiency Pin Selectable Burst Mode® Operation 45μA Quiescent Current in Burst Mode Operation 1.2MHz (LTC3523) or 2.4MHz (LTC3523-2) Switching Frequency Independent Power Good Indicator Outputs Integrated Soft-Start Thermal and Overcurrent Protection VOUT OPERATION The LTC3523/LTC3523-2 step-up converters will maintain voltage regulation when the input voltage is above the output voltage. Since this mode will dissipate more power, the maximum output current is limited in order to maintain an acceptable junction temperature and is given by: IOUT(MAX ) = 250 – TA T 136 • ⎡(VIN + 1.5) – VOUT ⎤ ⎣ ⎦ where TA = ambient temperature. For example, at VIN = 4.5V, VOUT = 3.3V and TA = 85°C, the maximum output current is limited to 449mA. 3523fb 11 LTC3523/LTC3523-2 APPLICATIONS INFORMATION DUAL BUCK-BOOST AND STEP-UP CONVERTER OPERATION The LTC3523/LTC3523-2 can be operated in a cascaded configuration as shown in Figure 2, allowing buck-boost and step-up converter operation. Supply rail sequencing is achieved by feeding the step-up converter PGOOD1 VIN 1.8V TO 5.25V 4.7μF 10μH VIN1 VOUT1 STEP-UP OUTPUT 5V 100mA SW1 VOUT 10μF 768k 243k FB1 PGOOD1 SHDN1 VIN2 VBAT SW2 10pF LTC3523 FB2 MODE PGOOD2 SHDN2 VIN 182k 825k 10μF 4.7μH VOUT2 STEP-DOWN OUTPUT 3.3V 50mA into the step-down’s SHDN2 pin. Note that the overall 3.3V converter efficiency is the product of the individual efficiencies. GND1 GND2 GND3 100k VIN OFF ON 3523 F02a 100 90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 0.1 VIN = 2.4V VOUT1 = 5V VOUT2 = 3.3V fOSC = 1.2MHz BURST ENABLED 10 1 100 OUTPUT CURRENT (mA) 1000 3523 F02b 5V OUTPUT 3.3V OUTPUT Figure 2. Dual Converter Efficiency (Load Applied to Step-Down Output) 3523fb 12 LTC3523/LTC3523-2 TYPICAL APPLICATIONS Power Sequence Operation VIN 1.8V TO 3.2V 2-CELL ALKALINE + 4.7μF 4.7μH VIN1 VIN2 VBAT SW2 10pF VOUT 4.7μF 634k 365k FB1 PGOOD1 SHDN1 LTC3523 FB2 MODE PGOOD2 SHDN2 511k 511k 10μF 4.7μH SW1 VOUT2 STEP-DOWN OUTPUT 1.2V 200mA VOUT1 STEP-UP OUTPUT 3.3V 200mA GND1 GND2 GND3 100k VIN OFF ON 3523 TA02a VOUT1 2V/DIV PGOOD2 VOUT2 1V/DIV SHDN2 500μs/DIV 3523 TA02b 3523fb 13 LTC3523/LTC3523-2 TYPICAL APPLICATIONS Li-Ion to 5V/150mA, 2.5V/200mA VIN 2.5V TO 4.2V Li-Ion + 4.7μF 10μH VIN1 VIN2 VBAT SW2 10pF VOUT 768k 243k 10μF FB2 MODE PGOOD2 SHDN2 VIN 4.7μH SW1 VOUT1 STEP-UP OUTPUT 5V 150mA VOUT2 STEP-DOWN OUTPUT 2.5V 200mA 10μF 768k 243k FB1 PGOOD1 SHDN1 LTC3523 GND1 GND2 GND3 OFF ON OFF ON 3523 TA03 Efficiency and Power Loss vs Load Current 100 90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 0 P0WER LOSS VIN = 3.6V VOUT1 = 5V VOUT2 = 2.5V fOSC = 1.2MHz STEP-UP STEP-DOWN 10 1 100 LOAD CURRENT (mA) 0 1000 3523 TA03b 1000 EFFICIENCY 100 POWER LOSS (mW) 3523fb 10 1 14 LTC3523/LTC3523-2 PACKAGE DESCRIPTION UD Package 16-Lead Plastic QFN (3mm × 3mm) (Reference LTC DWG # 05-08-1691) 0.70 0.05 3.50 0.05 2.10 1.45 0.05 0.05 (4 SIDES) PACKAGE OUTLINE 0.25 0.05 0.50 BSC RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 0.75 0.05 BOTTOM VIEW—EXPOSED PAD R = 0.115 TYP 15 16 0.40 1 1.45 0.10 (4-SIDES) 2 0.10 PIN 1 NOTCH R = 0.20 TYP OR 0.25 45 CHAMFER 3.00 0.10 (4 SIDES) PIN 1 TOP MARK (NOTE 6) (UD16) QFN 0904 0.200 REF 0.00 – 0.05 NOTE: 1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WEED-2) 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 0.15mm 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 0.25 0.05 0.50 BSC 3523fb 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. 15 LTC3523/LTC3523-2 RELATED PARTS PART NUMBER LTC3400/LTC3400B LTC3401 LTC3402 LTC3421 LTC3422 LTC3426 LTC3427 LTC3429/LTC3429B LTC3459 LTC3525-3 LTC3525-3.3 LTC3525-5 LTC3526/LTC3526L LTC3526B LTC3528/LTC3528B DESCRIPTION 600mA (ISW), 1.2MHz, Synchronous Step-Up DC/DC Converters 1A (ISW), 3MHz, Synchronous Step-Up DC/DC Converter 2A (ISW), 3MHz, Synchronous Step-Up DC/DC Converter 3A (ISW), 3MHz, Synchronous Step-Up DC/DC Converter with Output Disconnect Converter 1.5A (ISW), 3MHz, Synchronous Step-Up DC/DC with Output Disconnect Converter 2A (ISW), 1.5MHz, Step-Up DC/DC Converter 500mA (ISW), 1.25MHz, Synchronous Step-Up DC/DC with Output Disconnect Converter 600mA (ISW), 550kHz, Synchronous Step-Up DC/DC Converters Soft-Start/Output Disconnect 80mA (ISW), Synchronous Step-Up DC/DC Converter COMMENTS 92% Efficiency, VIN: 0.85V to 5V, VOUT(MAX) = 5V, IQ = 19μA/300μA, ISD < 1μA, ThinSOTTM Package 97% Efficiency, VIN: 0.85V to 5V, VOUT(MAX) = 5.5V, IQ = 38μA, ISD < 1μA, 10-Pin MS Package 97% Efficiency, VIN: 0.85V to 5V, VOUT(MAX) = 5.5V, IQ = 38μA, ISD < 1μA, 10-Pin MS Package 94% Efficiency, VIN: 0.85V to 4.5V, VOUT(MAX) = 5.25V, IQ = 12μA, ISD < 1μA, 24-Pin (4mm × 4mm) QFN Package 94% Efficiency, VIN: 0.85V to 4.5V, VOUT(MAX) = 5.25V, IQ = 25μA, ISD < 1μA, 10-Pin (3mm × 3mm) DFN Package 92% Efficiency, VIN: 1.6V to 5.5V, VOUT(MAX) = 5V, IQ = 600μA, ISD < 1μA, ThinSOT Package 94% Efficiency, VIN: 1.8V to 5V, VOUT(MAX) = 5.25V, IQ = 350μA, ISD < 1μA, 6-Pin (2mm × 2mm) DFN Package 96% Efficiency, VIN: 0.85V to 4.3V, VOUT(MAX) = 5V, IQ = 20μA, ISD < 1μA, ThinSOT Package 92% Efficiency, VIN: 1.5V to 5.5V, VOUT(MAX) = 10V, IQ = 10μA, ISD < 1μA, ThinSOT Package 400mA (ISW), Synchronous Step-Up DC/DC Converters with Output 94% Efficiency, VIN: 0.85V to 4V, VOUT(MAX) = 5V, Disconnect IQ = 7μA, ISD < 1μA, SC-70 Package 500mA (ISW), 1MHz Synchronous Step-Up DC/DC Converters with Output Disconnect 1A (ISW), 1MHz Synchronous Step-Up DC/DC Converters with Output Disconnect 94% Efficiency, VIN: 0.85V to 5V, VOUT(MAX) = 5.25V, IQ = 9μA, ISD < 1μA, 6-Pin (2mm × 2mm) DFN Package 94% Efficiency, VIN: 0.85V to 5V, VOUT(MAX) = 5.25V, IQ = 10μA, ISD < 1μA, 8-Pin (2mm × 3mm) DFN Package ThinSOT is a trademark of Linear Technology Corporation. 3523fb 16 Linear Technology Corporation (408) 432-1900 ● FAX: (408) 434-0507 ● LT 1108 REV B • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 www.linear.com © LINEAR TECHNOLOGY CORPORATION 2008