LTC3528BEDDB-2-PBF

LTC3528B-2 1A, 2MHz Synchronous Step-Up DC/DC Converter in 2mm × 3mm DFN FEATURES n n n n n n n n n n n n n n n DESCRIPTION The LTC®3528B-2 is a synchronous, fixed frequency step-up DC/DC converter with output disconnect. High efficiency synchronous rectification, in addition to a 700mV start-up voltage and operation down to 500mV once started, provides longer run-time for single or multiple cell battery-powered products. A switching frequency of 2MHz minimizes solution footprint by allowing the use of tiny, low profile inductors and ceramic capacitors. The current mode PWM is internally compensated, simplifying the design process. The LTC3528B-2 features continuous switching at light loads. Anti-ringing circuitry reduces EMI by damping the inductor in discontinuous mode. Additional features include a low shutdown current, open-drain power good output, shortcircuit protection and thermal overload protection. The LTC3528B-2 is offered in an 8-lead 2mm × 3mm × 0.75mm DFN package. L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Delivers 3.3V at 200mA from a Single Alkaline/ NiMH Cell or 3.3V at 400mA from Two Cells VIN Start-Up Voltage: 700mV 0.50V to 5.5V Input Range 1.6V to 5.25V VOUT Range Up to 94% Efficiency Output Disconnect 2MHz Fixed Frequency Operation VIN > VOUT Operation Integrated Soft-Start Current Mode Control with Internal Compensation Low Noise PWM Operation Internal Synchronous Rectifier Logic Controlled Shutdown: (VIN + 0.24V). (Refer to Block Diagram) Anti-Ringing Control The anti-ringing control connects a resistor across the inductor to prevent high frequency ringing on the SW pin during discontinuous current mode operation. The ringing of the resonant circuit formed by L and CSW (capacitance on SW pin) is low energy, but can cause EMI radiation. Output Disconnect The LTC3528B-2 is designed to allow true output disconnect by eliminating body diode conduction of the internal P-channel MOSFET rectifier. This allows for VOUT to go to zero volts during shutdown, drawing no current from the input source. It also enables inrush current limiting at turnon, minimizing surge currents seen by the input supply. Note that to obtain the advantages of output disconnect, a Schottky diode cannot be connected between SW and VOUT. The output disconnect feature also allows VOUT to be forced above the programmed regulation voltage, without any reverse current into a battery on VIN. Thermal Shutdown If the die temperature exceeds 160°C, the LTC3528B-2 enters thermal shutdown. All switches will be turned off and the soft-start capacitor will be discharged. The device will be enabled again when the die temperature drops by approximately 15°C. 3528b2f 9 LTC3528B-2 APPLICATIONS INFORMATION VIN > VOUT OPERATION The LTC3528B-2 maintains voltage regulation even when the input voltage is above the desired output voltage. Note that the efficiency is much lower in this mode, and the maximum output current capability will be less. Refer to the Typical Performance Characteristics. SHORT-CIRCUIT PROTECTION The LTC3528B-2 output disconnect feature allows an output short circuit while maintaining a maximum internally set current limit. To reduce power dissipation under shortcircuit conditions, the peak switch current limit is reduced to 750mA (typical). SCHOTTKY DIODE Although not required, adding a Schottky diode from SW to VOUT will improve efficiency by about 2%. Note that this defeats the output disconnect and short-circuit protection features. PCB LAYOUT GUIDELINES The high speed operation of the LTC3528B-2 demands careful attention to board layout. A careless layout will not produce the advertised performance. Figure 1 shows the recommended component placement. A large ground copper area with the package backside metal pad properly + VIN CIN soldered will help to lower the chip temperature. A multilayer board with a separate ground plane is ideal, but not absolutely necessary. COMPONENT SELECTION Inductor Selection The LTC3528B-2 can utilize small surface mount chip inductors due to their fast 2MHz switching frequency. Inductor values between 1.5μH and 3.3μH are suitable for most applications. Larger values of inductance will allow slightly greater output current capability by reducing the inductor ripple current. Increasing the inductance above 10μH will increase size while providing little improvement in output current capability. The minimum inductance value is given by: L> where: Ripple = Allowable inductor current ripple (amps peakpeak) VIN(MIN) = Minimum input voltage VOUT(MAX) = Maximum output voltage VIN(MIN) • VOUT(MAX) – VIN(MIN) 2 • Ripple • VOUT(MAX) ( ) µH SHDN 1 8 VIN FB 2 LTC3528B-2 PGOOD 3 7 SGND 6 PGND VOUT 4 COUT 5 SW 35282 F01 MULTIPLE VIAS TO GROUND PLANE Figure 1. Recommended Component Placement for Single Layer Board 3528b2f 10 LTC3528B-2 APPLICATIONS INFORMATION The inductor current ripple is typically set for 20% to 40% of the maximum inductor current. High frequency ferrite core inductor materials reduce frequency dependent power losses compared to cheaper powdered iron types, improving efficiency. The inductor should have low ESR (series resistance of the windings) to reduce the I2R power losses, and must be able to handle the peak inductor current without saturating. Molded chokes and some chip inductors usually do not have enough core area to support the peak inductor currents of 1.5A seen on the LTC3528B-2. To minimize radiated noise, use a shielded inductor. See Table 1 for suggested components and suppliers. Table 1. Recommended Inductors VENDOR Coilcraft (847) 639-6400 www.coilcraft.com Coiltronics Sumida (847) 956-0666 www.sumida.com TDK Toko (408) 432-8282 www.tokoam.com Wurth (201) 785-8800 www.we-online.com PART/STYLE DO1606T, MSS5131, MSS5121 MSS6122, MOS6020 ME3220, DO1608C 1812PS SD12, SD14, SD20 SD25, SD52 CD43 CDC5D23B CDRH5D18 VLP VLF , VLCF SLF VLS ,, D53, D62, D63 D73, D75 WE-TPC type M, MH A 10μF to 22μF output capacitor is sufficient for most applications. Values larger than 22μF 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. The internal loop compensation of the LTC3528B-2 is designed to be stable with output capacitor values of 10μF or greater. Although ceramic capacitors are recommended, low ESR tantalum capacitors may be used as well. A small ceramic capacitor in parallel with a larger tantalum capacitor may be used in demanding applications which have large load transients. Another method of improving the transient response is to add a small feed-forward capacitor across the top resistor of the feedback divider (from VOUT to FB). A typical value of 33pF 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 10μF 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 Output and Input Capacitor Selection Low ESR (equivalent series resistance) 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. 3528b2f 11 LTC3528B-2 TYPICAL APPLICATIONS 1 Cell to 1.8V 100 2.2μH 90 80 VIN 0.88V TO 1.6V 4.7μF VIN VOUT 499k 68pF EFFICIENCY (%) SW VOUT 1.8V 250mA 10μF 1M 35282 TA02a Efficiency 70 60 50 40 30 20 10 0.1 1 VIN = 0.9V VIN = 1.2V VIN = 1.5V 10 100 LOAD CURRENT (mA) 1000 35282 TA02b LTC3528B-2 PGOOD FB OFF ON SHDN GND Dual 1 Cell to 1.8V, 3V Sequenced Supply 2.2μH SW VIN 0.88V TO 1.6V 4.7μF 475k VIN VOUT 499k 68pF VOUT1 1.8V 250mA 10μF LTC3528B-2 PGOOD FB Output Voltage Sequencing VOUT2 OFF ON SHDN GND 1M 2.2μH 0.5V/DIV VOUT1 VIN PGOOD1 SW VIN 4.7μF VOUT 499k 68pF VOUT2 3V 200mA 200μs/DIV 10μF 35282 TA03b LTC3528B-2 PGOOD SHDN GND FB 324k 3528 TA03a 3528b2f 12 LTC3528B-2 TYPICAL APPLICATIONS 1 Cell to 3.3V 90 2.2μH 80 SW VIN 0.88V TO 1.6V 4.7μF VIN VOUT 499k 68pF VOUT 3.3V 200mA 10μF 287k 35282 TA04a Efficiency 70 EFFICIENCY (%) 60 50 40 30 20 10 1 10 100 LOAD CURRENT (mA) VIN = 0.9V VIN = 1.2V VIN = 1.5V 1000 36282 TA04b LTC3528B-2 PGOOD FB OFF ON SHDN GND 2 Cell to 3.3V 100 2.2μH 90 SW VIN 1.8V TO 3.2V 4.7μF VIN VOUT 499k 68pF 80 EFFICIENCY (%) VOUT 3.3V 400mA 10μF 287k 35282 TA05a Efficiency 70 60 50 40 30 20 10 0.1 1 VIN = 1.8V VIN = 2.4V VIN = 3V 10 100 LOAD CURRENT (mA) 1000 35282 TA05b LTC3528B-2 PGOOD FB OFF ON SHDN GND 3528b2f 13 LTC3528B-2 TYPICAL APPLICATIONS 2 Cell to 5V 100 2.2μH 90 80 VIN 1.8V TO 3.2V 4.7μF VIN VOUT 1M 22μF 316k 35282 TA06a Efficiency EFFICIENCY (%) SW VOUT 5V 300mA 70 60 50 40 30 20 10 0.1 1 VIN = 1.8V VIN = 2.4V VIN = 3V 10 100 LOAD CURRENT (mA) 1000 35282 TA06b LTC3528B-2 PGOOD FB OFF ON SHDN GND Li-Ion to 5V 100 2.2μH 90 80 VIN 2.7V TO 4.2V 4.7μF VIN VOUT 1M 22μF 316k 35282 TA07a Efficiency EFFICIENCY (%) SW VOUT 5V 400mA 70 60 50 40 30 20 10 0.1 1 VIN = 2.8V VIN = 3.6V VIN = 4.2V 10 100 LOAD CURRENT (mA) 1000 35282 TA07b LTC3528B-2 PGOOD FB OFF ON SHDN GND 3528b2f 14 LTC3528B-2 PACKAGE DESCRIPTION DDB Package 8-Lead Plastic DFN (3mm × 2mm) (Reference LTC DWG # 05-08-1702 Rev B) 0.61 ± 0.05 (2 SIDES) 0.70 ± 0.05 2.55 ± 0.05 1.15 ± 0.05 PACKAGE OUTLINE 0.25 ± 0.05 0.50 BSC 2.20 ± 0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS R = 0.115 TYP 5 0.40 ± 0.10 8 3.00 ± 0.10 (2 SIDES) R = 0.05 TYP PIN 1 BAR TOP MARK (SEE NOTE 6) 2.00 ± 0.10 (2 SIDES) 0.56 ± 0.05 (2 SIDES) 0.75 ± 0.05 0.200 REF 4 0.25 ± 0.05 2.15 ± 0.05 (2 SIDES) 1 0.50 BSC PIN 1 R = 0.20 OR 0.25 × 45° CHAMFER (DDB8) DFN 0905 REV B 0 – 0.05 BOTTOM VIEW—EXPOSED PAD NOTE: 1. DRAWING CONFORMS TO VERSION (WECD-1) IN JEDEC PACKAGE OUTLINE M0-229 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 3528b2f 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 LTC3528B-2 RELATED PARTS PART NUMBER LTC3400/LTC3400B LTC3421 LTC3422 LTC3426 LTC3427 LTC3429/LTC3429B LTC3458/LTC3458L LTC3459 LT®3494/LT3494A LTC3523/LTC3523-2 DESCRIPTION 600mA (ISW), 1.2MHz, Synchronous Step-Up DC/DC Converters 3A (ISW), 3MHz, Synchronous Step-Up DC/DC Converter with Output Disconnect 1.5A (ISW), 3MHz Synchronous Step-Up DC/DC Converter with Output Disconnect 2A (ISW), 1.5MHz, Step-Up DC/DC Converter 500mA (ISW), 1.25MHz, Synchronous Step-Up DC/DC Converter with Output Disconnect 600mA (ISW), 550kHz, Synchronous Step-Up DC/DC Converter with Output Disconnect and Soft-Start 1.4A/1.7A (ISW), 1.5MHz, Synchronous Step-Up DC/DC Converter 80mA (ISW), Synchronous Step-Up DC/DC Converter 180mA/350mA (ISW), High Efficiency Step-Up DC/DC Converter with Output Disconnect 600mA (ISW), Step-Up and 400mA Synchronous Step-Down 1.2MHz/2.4MHz DC/DC Converters with Output Disconnect 500mA (ISW), 1MHz Synchronous Step-Up DC/DC Converters with Output Disconnect Dual 800mA/400mA (ISW), 2.2MHz, Synchronous Step-Up DC/DC Converter with Output Disconnect COMMENTS 92% Efficiency VIN: 0.85V to 5V, VOUT(MAX) = 5V, IQ = 19μA/300μA, ISD < 1μA, ThinSOTTM Package 94% Efficiency VIN: 0.85V to 4.5V, VOUT(MAX) = 5.25V, IQ = 12μA, ISD < 1μA, 4mm × 4mm QFN24 Package 94% Efficiency VIN: 0.85V to 4.5V, VOUT(MAX) = 5.25V, IQ = 25µA, ISD < 1µA, 3mm × 3mm DFN10 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, 2mm × 2mm DFN6 Package 96% Efficiency VIN: 0.85V to 4.3V, VOUT(MAX) = 5V, IQ = 20μA, ISD < 1μA, ThinSOT Package 94% Efficiency VIN: 0.85V to 6V, VOUT(MAX) = 7.5V/6V, IQ = 15μA, ISD < 1μA, 3mm × 4mm DFN12 Package 92% Efficiency VIN: 1.5V to 5.5V, VOUT(MAX) = 10V, IQ = 10μA, ISD < 1μA, ThinSOT Package 85% Efficiency VIN: 2.3V to 16V, VOUT(MAX) = 38V, IQ = 65μA, ISD < 1μA, 2mm × 3mm DFN6, ThinSOT Packages 94% Efficiency VIN: 1.8V to 5.5V, VOUT(MAX) = 5.25V, IQ = 45μA, ISD < 1μA, 3mm × 3mm QFN16 94% Efficiency, VIN: 0.85V to 5V, VOUT(MAX) = 5.25V, IQ = 9μA, ISD < 1μA, 2mm × 2mm DFN6 Package 94% Efficiency, VIN: 0.7V to 5V, VOUT(MAX) = 5.25V, IQ = 12μA, ISD < 1μA, 3mm × 3mm QFN16 Package LTC3526/LTC3526L LTC3526B LTC3527/LTC3527-1 LTC3528/LTC3528B LTC3537 1A (ISW), 1MHz Synchronous Step-Up DC/DC Converters 94% Efficiency, VIN: 0.7V to 5.5V, VOUT(MAX) = 5.25V, IQ = 12μA, ISD < 1μA, 3mm × 2mm DFN8 Package with Output Disconnect 600mA, 2.2MHz Synchronous Step-Up DC/DC Converter with Output Disconnect and 100mA LDO 94% Efficiency, VIN: 0.7V to 5V, VOUT(MAX) = 5.25V, IQ = 30μA, ISD < 1μA, 3mm × 3mm QFN16 Package ThinSOT is a trademark of Linear Technology Corporation. 3528b2f 16 Linear Technology Corporation (408) 432-1900 ● FAX: (408) 434-0507 ● LT 0708 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 www.linear.com © LINEAR TECHNOLOGY CORPORATION 2008