LTC3539EDCB-2-TRPBF

LTC3539/LTC3539-2 2A, 1MHz/2MHz Synchronous Step-Up DC/DC Converters FEATURES n n n n n n n n n n n n n DESCRIPTION The LTC®3539/LTC3539-2 are synchronous, 2A step-up DC/DC converters with output disconnect. Synchronous rectification enables high efficiency in the low profile 2mm × 3mm DFN package. Battery life is extended with a 700mV start-up voltage and operation down to 500mV once started. A switching frequency of 1MHz (LTC3539) or 2MHz (LTC3539-2) minimizes solution footprint by allowing the use of tiny, low profile inductors and ceramic capacitors. The current mode PWM design is internally compensated, reducing external parts count. The LTC3539/LTC3539-2 feature a pin-enabled automatic Burst Mode operation at light load conditions. Anti-ring circuitry reduces EMI by damping the inductor in discontinuous mode. Additional features include a low shutdown current of under 1μA and thermal overload protection. The LTC3539/LTC3539-2 are offered in a 2mm × 3mm × 0.75mm DFN 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. Delivers 3.3V at 900mA From 2 Alkaline/NiMH Cells Delivers 5V at 900mA From a Lithium-Polymer Battery VIN Start-Up Voltage: 700mV 1.5V to 5.25V VOUT Range Up to 94% Efficiency VIN > VOUT Operation 1MHz (LTC3539) or 2MHz (LTC3539-2) Fixed Frequency Operation Output Disconnect Selectable Burst Mode® or PWM Operation 10μA Quiescent Current Logic Controlled Shutdown: VOUT operation and short circuit protection features. PCB LAYOUT GUIDELINES The high speed operation of the LTC3539 demands careful attention to board layout. A careless layout will result in reduced performance. Figure 1 shows the recommended component placement. A large ground pin copper area will help to lower the die temperature. A multilayer board with a separate ground plane is ideal. L> Where: f = 1 for the LTC3539 or 2.2 for the LTC3539-2 Ripple = allowable inductor current ripple (Amps peak-to-peak) VIN(MIN) = minimum input voltage VOUT(MAX) = maximum output voltage The inductor current ripple is typically set for 20% to 40% of the maximum inductor current. High frequency ferrite core inductor materials improve efficiency by reducing frequency dependent power losses compared to cheaper powdered iron types. The inductor should have low ESR (series resistance of the windings) to reduce the I2R power losses, and must accomodate the peak inductor current without saturating. Molded chokes and some chip inductors usually do not have enough core area to support the peak inductor current of 2.6A seen on the LTC3539. To minimize radiated noise, use a shielded inductor. See Table 1 for suggested suppliers and representative components. *Single cell applications (VIN < 1.6V) should use a 2.2μH inductor for the LTC3539 MULTIPLE VIAS TO GROUND PLANE 3539 F01 COMPONENT SELECTION Inductor Selection The LTC3539 can utilize small surface mount and chip inductors due to the high switching frequency. Inductor values between 3.3μH and 4.7μH for the LTC3539 and between 1.5μH and 2.5μH for the LTC3539-2 are suitable for most applications*. Larger values of inductance will allow slightly greater output current capability (and lower the Burst Mode threshold) by reducing the inductor ripple current. However, increasing the inductance above 10μH will increase size while providing little improvement in output current capability. The minimum inductance value is given by: VIN(MIN) • ( VOUT(MAX ) − VIN(MIN) ) Ripple • VOUT(MAX ) • f LTC3539 SW 1 PGND 2 GND 3 VIN 4 8 VOUT 7 MODE 6 FB 5 SHDN MINIMIZE TRACE ON FB AND SW + VIN Figure 1. Recommended Component Placement for Single Layer Board 3539f 9 LTC3539/LTC3539-2 APPLICATIONS INFORMATION Table 1. Representative Inductors VENDOR Coilcraft (847) 639-6400 www.coilcraft.com Murata www.murata.com Sumida (847) 956-0666 www.sumida.com TDK (847) 803-6100 www.component.tdk.com Toko (408) 432-8282 www.tokoam.com Wurth (201) 785-8800 www.we-online.com PART/STYLE MSS5131 LPS4018-222 MSS6132 MOS6020 LQH55D LQH66S CDRH4D22 CDRH4D28C CDRH5D28 CDR6D23 VLF5014ST An output capacitor of up to 100μF is required at lower output voltages. Even with VOUT greater than 3V, larger values up to 100μF may be used to obtain extremely low output voltage ripple and improve transient response. X5R and X7R dielectric materials are preferred for their ability to maintain capacitance over wide voltage and temperature ranges. Y5V types should not be used. A small ceramic capacitor in parallel with a larger tantalum capacitor may be used in demanding applications which have large load transients. A feedforward capacitor across the top resistor of the feedback divider (from VOUT to FB) is usually required to improve transient response. A typical value of 22pF will generally suffice. Low ESR input capacitors reduce input switching noise and reduce the peak current drawn from the battery. It follows that ceramic capacitors are also a good choice for input decoupling and should be located as close as possible to the device. A 2.2μF input capacitor is sufficient for most applications. Larger values may be used without limitations. Table 2 shows a list of several ceramic capacitor manufacturers. Consult the manufacturers directly for detailed information on their selection of ceramic parts. Table 2. Capacitor Vendor Information SUPPLIER AVX Murata Taiyo-Yuden TDK PHONE (803) 448-9411 (714) 852-2001 (408) 573-4150 (847) 803-6100 WEBSITE www.avxcorp.com www.murata.com www.t-yuden.com www.component.tdk.com D53LC D63LCB WE-TPC Type LH, X WE-PD Type XS Output and Input Capacitor Selection The internal loop compensation of the LTC3539 is designed to be stable with output capacitor values of 10μF or greater. Although ceramic capacitors are recommended, low ESR (equivalent series resistance) tantalum capacitors may be used as well. Low ESR capacitors should be used to minimize the output voltage ripple. Multilayer ceramic capacitors are an excellent choice as they have extremely low ESR and are available in small footprints. A 22μF to 47μF output capacitor is sufficient for output voltages of 3V or greater. TYPICAL APPLICATIONS 1 Cell to 1.8V 2.2μH VIN 1V TO 1.6V 2.2μF VIN SW VOUT 1.8V 500mA 22μF* x5 VIN 0.9V TO 1.6V 2.2μF VIN SW VOUT 3.3V 350mA 22μF x2 1 Cell to 3.3V 2.2μH VIN 3V TO 4.5V 2.2μF Li-Ion Cell to 5V 2.2μH VIN SW VOUT 5V 750mA 22μF 309k 3539 TA04 LTC3539 PWM BURST MODE VOUT 1M OFF ON SHDN FB 1.91M 3539 TA02 LTC3539 PWM BURST MODE VOUT 1M OFF ON SHDN FB 562k 3539 TA03 LTC3539-2 PWM BURST MODE VOUT 1M OFF ON SHDN FB 22pF 22pF 22pF GND PGND *AT HIGH LOAD CURRENTS, A TANTALUM CAPACITOR WILL IMPROVE PERFORMANCE. GND PGND GND PGND 3539f 10 LTC3539/LTC3539-2 PACKAGE DESCRIPTION DCB Package 8-Lead Plastic DFN (2mm × 3mm) (Reference LTC DWG # 05-08-1718 Rev A) 0.70 ± 0.05 1.35 ± 0.05 1.65 ± 0.05 3.50 ± 0.05 2.10 ± 0.05 PACKAGE OUTLINE 0.25 ± 0.05 0.45 BSC 1.35 REF RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 2.00 ± 0.10 (2 SIDES) R = 0.115 TYP R = 0.05 5 TYP 0.40 ± 0.10 8 1.35 ± 0.10 3.00 ± 0.10 (2 SIDES) PIN 1 BAR TOP MARK (SEE NOTE 6) 4 0.200 REF 0.75 ± 0.05 1.35 REF BOTTOM VIEW—EXPOSED PAD 0.00 – 0.05 NOTE: 1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE 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 1 1.65 ± 0.10 PIN 1 NOTCH R = 0.20 OR 0.25 × 45° CHAMFER (DCB8) DFN 0106 REV A 0.23 ± 0.05 0.45 BSC 3539f 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. 11 LTC3539/LTC3539-2 RELATED PARTS PART NUMBER DESCRIPTION LTC3400/ LTC3400B LTC3401 LTC3402 LTC3421 LTC3422 LTC3423/ LTC3424 LTC3426 LTC3428 LTC3429 LTC3458 LTC3458L 600mA ISW, 1.2MHz, Synchronous Step-Up DC/DC Converters COMMENTS 92% Efficiency VIN: 0.85V to 5V, VOUT(MAX) = 5V, IQ = 19μA/300μA, ISD