LTC3539EDCB-2#TRMPBF

LTC3539/LTC3539-2 2A, 1MHz/2MHz Synchronous Step-Up DC/DC Converters FEATURES DESCRIPTION Delivers 3.3V at 900mA From 2 Alkaline/NiMH Cells Delivers 5V at 900mA From a Lithium-Polymer Battery n V Start-Up Voltage: 700mV IN n 1.5V to 5.25V V OUT Range n Up to 94% Efficiency n V > V IN OUT Operation n ±1.5% Feedback Voltage Tolerance n 1MHz (LTC3539) or 2MHz (LTC3539-2) Fixed Frequency Operation n Output Disconnect n Selectable Burst Mode® or PWM Operation n 10µA Quiescent Current n 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. LTC3539 SW 1 PGND 2 GND 3 VIN + VIN 4 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. 8 VOUT 7 MODE 6 FB MINIMIZE TRACE ON FB AND SW 5 SHDN MULTIPLE VIAS TO GROUND PLANE L> VIN(MIN) • (VOUT(MAX) − VIN(MIN) ) Ripple • VOUT(MAX) • f Where: f = 1 for the LTC3539 or 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 accommodate 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 3539 F01 Figure 1. Recommended Component Placement for Single Layer Board 35392fc For more information www.linear.com/3539/3539-2 9 LTC3539/LTC3539-2 APPLICATIONS INFORMATION 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. Table 1. Representative Inductors VENDOR PART/STYLE Coilcraft (847) 639-6400 www.coilcraft.com MSS5131 LPS4018-222 MSS6132 MOS6020 Murata www.murata.com LQH55D LQH66S Sumida (847) 956-0666 www.sumida.com CDRH4D22 CDRH4D28C CDRH5D28 CDR6D23 TDK (847) 803-6100 www.component.tdk.com VLF5014ST Toko (408) 432-8282 www.tokoam.com D53LC D63LCB Würth (201) 785-8800 www.we-online.com WE-TPC Type LH, X WE-PD Type XS 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 33pF will generally suffice. Output and Input Capacitor Selection The internal loop compensation of the LTC3539 is designed to be stable with output capacitor values of 22µF 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. 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 PHONE WEBSITE AVX (803) 448-9411 www.avxcorp.com Murata (714) 852-2001 www.murata.com Taiyo-Yuden (408) 573-4150 www.t-yuden.com TDK (847) 803-6100 www.component.tdk.com 35392fc 10 For more information www.linear.com/3539/3539-2 LTC3539/LTC3539-2 TYPICAL APPLICATIONS 1 Cell to 1.8V 2.2µH VIN 1V TO 1.6V 2.2µF SW VIN LTC3539 PWM BURST MODE VOUT 1M OFF ON SHDN 33pF FB GND PGND 22µF* ×2 1.91M *AT HIGH LOAD CURRENTS, A TANTALUM CAPACITOR WILL IMPROVE PERFORMANCE. VOUT 1.8V 500mA 3539 TA02 1 Cell to 3.3V 2.2µH VIN 0.9V TO 1.6V 2.2µF VIN SW LTC3539 PWM BURST MODE VOUT 1M OFF ON SHDN 33pF FB GND PGND VOUT 3.3V 350mA 22µF ×2 562k 3539 TA03 Li-Ion Cell to 5V 2.2µH VIN 3V TO 4.5V 2.2µF VIN SW LTC3539-2 PWM BURST MODE VOUT 1M OFF ON SHDN 33pF FB GND PGND VOUT 5V 750mA 22µF ×2 309k 3539 TA04 35392fc For more information www.linear.com/3539/3539-2 11 LTC3539/LTC3539-2 PACKAGE DESCRIPTION Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. DCB Package 8-Lead Plastic DFN (2mm × 3mm) (Reference LTC DWG # 05-08-1718 Rev A) 0.70 ±0.05 1.35 ±0.05 3.50 ±0.05 1.65 ±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 R = 0.115 TYP R = 0.05 5 TYP 2.00 ±0.10 (2 SIDES) 0.40 ±0.10 8 1.35 ±0.10 1.65 ±0.10 3.00 ±0.10 (2 SIDES) PIN 1 NOTCH R = 0.20 OR 0.25 × 45° CHAMFER PIN 1 BAR TOP MARK (SEE NOTE 6) (DCB8) DFN 0106 REV A 4 0.200 REF 1 0.23 ±0.05 0.45 BSC 0.75 ±0.05 1.35 REF 0.00 – 0.05 BOTTOM VIEW—EXPOSED PAD 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 35392fc 12 For more information www.linear.com/3539/3539-2 LTC3539/LTC3539-2 REVISION HISTORY (Revision history begins at Rev B) REV DATE DESCRIPTION B 02/13 Improved feedback voltage tolerance spec C 09/14 PAGE NUMBER 1, 2 Clarified Burst Mode operation 8 Corrected Block Diagram schematic 6 35392fc 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. For more information www.linear.com/3539/3539-2 13 LTC3539/LTC3539-2 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC3400/ LTC3400B 600mA ISW, 1.2MHz, Synchronous Step-Up DC/DC Converters 92% Efficiency VIN: 0.85V to 5V, VOUT(MAX) = 5V, IQ = 19µA/300µA, ISD