LTC3528BEDDB-2#TRPBF

LTC3528B-2 1A, 2MHz Synchronous Step-Up DC/DC Converter in 2mm × 3mm DFN FEATURES DESCRIPTION Delivers 3.3V at 200mA from a Single Alkaline/ NiMH Cell or 3.3V at 400mA from Two Cells n V Start-Up Voltage: 700mV IN n 0.50V to 5.5V Input Range n 1.6V to 5.25V V OUT Range n Up to 94% Efficiency n Output Disconnect n 2MHz Fixed Frequency Operation n V > V IN OUT Operation n Integrated Soft-Start n Current Mode Control with Internal Compensation n Low Noise PWM Operation n Internal Synchronous Rectifier n Logic Controlled Shutdown: (VCNTRL/(VIN + 0.4) – 1) MΩ ZETEX ZC2811E VCNTRL 1M Figure 1. Recommended Shutdown Circuits when Driving SHDN Above VIN 3528b2fa 8 LTC3528B-2 OPERATION (Refer to Block Diagram) Error Amplifier Synchronous Rectifier The error amplifier is a transconductance type. The noninverting input is internally connected to the 1.20V reference and the inverting input is connected to FB. Clamps limit the minimum and maximum error amp output voltage for improved large-signal transient response. Power converter control loop compensation is provided internally. A voltage divider from VOUT to ground programs the output voltage via FB from 1.6V to 5.25V. To control inrush current and to prevent the inductor current from running away when VOUT is close to VIN, the P-channel MOSFET synchronous rectifier is only enabled when VOUT > (VIN + 0.24V). Anti-Ringing Control  R2 VOUT = 1.20V • 1+   R1 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. Current Sensing Output Disconnect Lossless current sensing converts the peak current signal of the N-channel MOSFET switch into a voltage which is summed with the internal slope compensation. The summed signal is compared to the error amplifier output to provide a peak current control command for the PWM. Current Limit The current limit comparator shuts off the N-channel MOSFET switch once its threshold is reached. The current limit comparator delay to output is typically 60ns. Peak switch current is limited to approximately 1.5A, independent of input or output voltage, unless VOUT falls below 0.7V, in which case the current limit is cut in half. Zero Current Comparator The zero current comparator monitors the inductor current to the output and shuts off the synchronous rectifier when this current reduces to approximately 20mA. This prevents the inductor current from reversing in polarity, improving efficiency at light loads. 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. 3528b2fa 9 LTC3528B-2 APPLICATIONS INFORMATION VIN > VOUT OPERATION soldered will help to lower the chip temperature. A multilayer board with a separate ground plane is ideal, but not absolutely necessary. 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. 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. 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 The minimum inductance value is given by: 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. L> ( VIN(MIN) • VOUT(MAX) – VIN(MIN) 2 • Ripple • VOUT(MAX) ) µH where: PCB LAYOUT GUIDELINES Ripple = Allowable inductor current ripple (amps peakpeak) The high speed operation of the LTC3528B-2 demands careful attention to board layout. A careless layout will not produce the advertised performance. Figure 2 shows the recommended component placement. A large ground copper area with the package backside metal pad properly VIN(MIN) = Minimum input voltage VOUT(MAX) = Maximum output voltage VIN + SHDN 1 CIN 8 VIN 7 SGND FB 2 LTC3528B-2 PGOOD 3 VOUT 4 COUT 6 PGND 5 SW 35282 F02 MULTIPLE VIAS TO GROUND PLANE Figure 2. Recommended Component Placement for Single Layer Board 3528b2fa 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 PART/STYLE Coilcraft (847) 639-6400 www.coilcraft.com DO1606T, MSS5131, MSS5121 MSS6122, MOS6020 ME3220, DO1608C 1812PS Coiltronics SD12, SD14, SD20 SD25, SD52 Sumida (847) 956-0666 www.sumida.com CD43 CDC5D23B CDRH5D18 TDK VLP, VLF VLCF, SLF, VLS Toko (408) 432-8282 www.tokoam.com D53, D62, D63 D73, D75 Wurth (201) 785-8800 www.we-online.com WE-TPC type M, MH 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. 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 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 3528b2fa 11 LTC3528B-2 TYPICAL APPLICATIONS 1 Cell to 1.8V Efficiency 100 90 2.2µH 80 SW VIN 4.7µF 68pF 499k LTC3528B-2 PGOOD OFF ON VOUT 1.8V 250mA VOUT EFFICIENCY (%) VIN 0.88V TO 1.6V 10µF FB SHDN 1M GND 70 60 50 40 30 VIN = 0.9V VIN = 1.2V VIN = 1.5V 20 35282 TA02a 10 0.1 1 10 100 LOAD CURRENT (mA) 1000 35282 TA02b Dual 1 Cell to 1.8V, 3V Sequenced Supply 2.2µH SW VIN 0.88V TO 1.6V VOUT VIN 4.7µF 475k LTC3528B-2 68pF SHDN VOUT2 1M GND VOUT1 VIN PGOOD1 0.5V/DIV 2.2µH SW VIN 4.7µF Output Voltage Sequencing 10µF FB PGOOD OFF ON 499k VOUT1 1.8V 250mA VOUT LTC3528B-2 PGOOD SHDN GND 499k 68pF VOUT2 3V 200mA 200µs/DIV 35282 TA03b 10µF FB 324k 3528 TA03a 3528b2fa 12 LTC3528B-2 TYPICAL APPLICATIONS 1 Cell to 3.3V Efficiency 90 2.2µH 80 VIN 4.7µF VOUT LTC3528B-2 68pF 10µF FB PGOOD OFF ON 499k SHDN VOUT 3.3V 200mA 70 EFFICIENCY (%) SW VIN 0.88V TO 1.6V 287k GND 60 50 40 30 VIN = 0.9V VIN = 1.2V VIN = 1.5V 20 35282 TA04a 10 1 10 100 LOAD CURRENT (mA) 1000 36282 TA04b 2 Cell to 3.3V Efficiency 100 2.2µH 90 VIN 4.7µF VOUT LTC3528B-2 PGOOD OFF ON SHDN GND 499k 68pF VOUT 3.3V 400mA 10µF FB 287k 80 EFFICIENCY (%) SW VIN 1.8V TO 3.2V 70 60 50 40 30 35282 TA05a VIN = 1.8V VIN = 2.4V VIN = 3V 20 10 0.1 1 10 100 LOAD CURRENT (mA) 1000 35282 TA05b 3528b2fa 13 LTC3528B-2 TYPICAL APPLICATIONS 2 Cell to 5V 2.2µH SW VIN 1.8V TO 3.2V VIN 4.7µF VOUT LTC3528B-2 PGOOD OFF ON 1M 22µF FB SHDN VOUT 5V 300mA 316k GND 35282 TA06a Efficiency 100 90 EFFICIENCY (%) 80 70 60 50 40 30 VIN = 1.8V VIN = 2.4V VIN = 3V 20 10 0.1 1 10 100 LOAD CURRENT (mA) 1000 35282 TA06b 3528b2fa 14 LTC3528B-2 TYPICAL APPLICATIONS Li-Ion to 5V 2.2µH SW VIN 2.7V TO 4.2V VIN 4.7µF LTC3528B-2 PGOOD OFF ON VOUT 5V 400mA VOUT 1M 22µF FB SHDN 316k GND 35282 TA07a Efficiency 100 90 EFFICIENCY (%) 80 70 60 50 40 30 VIN = 2.8V VIN = 3.6V VIN = 4.2V 20 10 0.1 1 10 100 LOAD CURRENT (mA) 1000 35282 TA07b 3528b2fa 15 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 3.00 ±0.10 (2 SIDES) R = 0.115 TYP 5 R = 0.05 TYP 0.40 ± 0.10 8 2.00 ±0.10 (2 SIDES) PIN 1 BAR TOP MARK (SEE NOTE 6) 0.56 ± 0.05 (2 SIDES) 0.200 REF 0.75 ±0.05 0 – 0.05 4 0.25 ± 0.05 1 PIN 1 R = 0.20 OR 0.25 × 45° CHAMFER (DDB8) DFN 0905 REV B 0.50 BSC 2.15 ±0.05 (2 SIDES) 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 3528b2fa 16 LTC3528B-2 REVISION HISTORY REV DATE DESCRIPTION A 01/11 Change to Operating Temperature Range PAGE NUMBER Update to Note 2 reflected in Electrical Characteristics 2 2, 3 Replaced graphs G14, G15, G16 and G17 5 Operations section update Pin 9 to read GND 6 Operations section update to Shutdown 8 3528b2fa 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. 17 LTC3528B-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 < 1µA, ThinSOTTM Package LTC3421 3A (ISW), 3MHz, Synchronous Step-Up DC/DC Converter with Output Disconnect 94% Efficiency VIN: 0.85V to 4.5V, VOUT(MAX) = 5.25V, IQ = 12µA, ISD < 1µA, 4mm × 4mm QFN24 Package LTC3422 1.5A (ISW), 3MHz Synchronous Step-Up DC/DC Converter with Output Disconnect 94% Efficiency VIN: 0.85V to 4.5V, VOUT(MAX) = 5.25V, IQ = 25µA, ISD < 1µA, 3mm × 3mm DFN10 Package LTC3426 2A (ISW), 1.5MHz, Step-Up DC/DC Converter 92% Efficiency VIN: 1.6V to 5.5V, VOUT(MAX) = 5V, IQ = 600µA, ISD < 1µA, ThinSOT Package LTC3427 500mA (ISW), 1.25MHz, Synchronous Step-Up DC/DC Converter with Output Disconnect 94% Efficiency VIN: 1.8V to 5V, VOUT(MAX) = 5.25V, IQ = 350µA ISD < 1µA, 2mm × 2mm DFN6 Package LTC3429/LTC3429B 600mA (ISW), 550kHz, Synchronous Step-Up DC/DC Converter with Output Disconnect and Soft-Start 96% Efficiency VIN: 0.85V to 4.3V, VOUT(MAX) = 5V, IQ = 20µA, ISD < 1µA, ThinSOT Package LTC3458/LTC3458L 1.4A/1.7A (ISW), 1.5MHz, Synchronous Step-Up DC/DC Converter 94% Efficiency VIN: 0.85V to 6V, VOUT(MAX) = 7.5V/6V, IQ = 15µA, ISD < 1µA, 3mm × 4mm DFN12 Package LTC3459 80mA (ISW), Synchronous Step-Up DC/DC Converter 92% Efficiency VIN: 1.5V to 5.5V, VOUT(MAX) = 10V, IQ = 10µA, ISD < 1µA, ThinSOT Package LT®3494/LT3494A 180mA/350mA (ISW), High Efficiency Step-Up DC/DC Converter with Output Disconnect 85% Efficiency VIN: 2.3V to 16V, VOUT(MAX) = 38V, IQ = 65µA, ISD < 1µA, 2mm × 3mm DFN6, ThinSOT Packages LTC3523/LTC3523-2 600mA (ISW), Step-Up and 400mA Synchronous Step-Down 1.2MHz/2.4MHz DC/DC Converters with Output Disconnect 94% Efficiency VIN: 1.8V to 5.5V, VOUT(MAX) = 5.25V, IQ = 45µA, ISD < 1µA, 3mm × 3mm QFN16 LTC3526/LTC3526L LTC3526B 500mA (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, 2mm × 2mm DFN6 Package LTC3527/LTC3527-1 Dual 800mA/400mA (ISW), 2.2MHz, Synchronous Step-Up DC/DC Converter with Output Disconnect 94% Efficiency, VIN: 0.7V to 5V, VOUT(MAX) = 5.25V, IQ = 12µA, ISD < 1µA, 3mm × 3mm QFN16 Package LTC3528/LTC3528B 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 LTC3537 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 3528b2fa 18 Linear Technology Corporation LT 0111 REV A • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com  LINEAR TECHNOLOGY CORPORATION 2008