LTC3772BETS8#TRPBF

LTC3772B Micropower No RSENSE Constant Frequency Step-Down DC/DC Controller U FEATURES DESCRIPTIO ■ The LTC®3772B is a constant frequency current mode step-down DC/DC controller in a low profile 8-lead SOT-23 (ThinSOTTM) and a 3mm × 2mm DFN package. The No RSENSETM architecture eliminates the need for a current sense resistor, improving efficiency and saving board space. ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ No Current Sense Resistor Required High Output Currents Easily Achieved Internal Soft-Start Ramps VOUT Wide VIN Range: 2.75V to 9.8V Low Dropout: 100% Duty Cycle Constant Frequency 550kHz Operation Low Ripple Pulse Skipping Operation at Light Load Output Voltage as Low as 0.8V ±1.5% Voltage Reference Accuracy Current Mode Operation for Excellent Line and Load Transient Response Only 8µA Supply Current in Shutdown Low Profile 8-Lead SOT-23 (1mm) and (3mm × 2mm) DFN (0.75mm) Packages The LTC3772B automatically switches into pulse skipping operation at light loads. It consumes only 200µA of quiescent current under a no-load condition. The LTC3772B incorporates an undervoltage lockout feature that shuts down the device when the input voltage falls below 2V. To maximize the runtime from a battery source, the external P-channel MOSFET is turned on continuously in dropout (100% duty cycle). High switching frequency of 550kHz allows the use of a small inductor and capacitors. An internal soft-start smoothly ramps the output voltage from zero to its regulation point. U APPLICATIO S ■ ■ ■ 1- or 2-Cell Li-Ion Battery-Powered Applications Wireless Devices Portable Computers Distributed Power Systems , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. ThinSOT and No RSENSE are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 5731694, 6127815. U ■ TYPICAL APPLICATIO Efficiency and Power Loss vs Load Current (Figure 5 Circuit) 550kHz Micropower Step-Down DC/DC Converter ITH/RUN VIN 2.75V TO 9.8V VIN LTC3772B SW 47µF VOUT 2.5V 2A 174k 60 0.1 50 40 POWER LOSS 30 3772B TA01 1 EFFICIENCY 70 3.3µH VFB 80 10µF PGATE 82.5k 90 POWER LOSS (W) GND 22pF 10 100 20k EFFICIENCY (%) 680pF 0.01 20 VIN = 3.3V VIN = 5V 10 0 1 10 100 1000 LOAD CURRENT (mA) 0.001 10000 3772B TA01b 3772bfa 1 LTC3772B W W U W ABSOLUTE MAXIMUM RATINGS (Note 1) Input Supply Voltage (VIN)........................ – 0.3V to 10V IPRG Voltage ............................... – 0.3V to (VIN + 0.3V) VFB, ITH/RUN Voltages ............................. – 0.3V to 2.4V SW Voltage ........... – 2V to (VIN + 1V) or 10V Maximum PGATE Peak Output Current (1µF) supply bypass capacitors. The discharged bypass capacitors are effectively put in parallel with COUT, causing a rapid drop in VOUT. No regulator can deliver enough current to prevent this problem if the load switch resistance is low and it is driven quickly. The only solution is to limit the rise time of the switch drive so that the load rise time is limited to approximately (25)(CLOAD). Thus a 10µF capacitor would require a 250µs rise time, limiting the charging current to about 200mA. Minimum On-Time Considerations Minimum on-time, tON(MIN), is the smallest amount of time that the LTC3772B is capable of turning the top MOSFET on and then off. It is determined by internal timing delays and the gate charge required to turn on the top MOSFET. The minimum on-time for the LTC3772B is about 250ns. Low duty cycle and high frequency applications may approach this minimum on-time limit and care should be taken to ensure that: tON(MIN) < VOUT f • VIN If the duty cycle falls below what can be accommodated by the minimum on-time, the LTC3772B will begin to skip cycles. The output voltage will continue to be regulated, but the ripple current and ripple voltage will increase. 3772bfa 14 LTC3772B U TYPICAL APPLICATIO S 550kHz Micropower, 1A, 2-Cell Li-Ion to 3.3VOUT Step-Down DC/DC Converter 100pF 15k ITH/RUN VIN CIN 22µF LTC3772B GND 56.2k Si2341DS PGATE IPRG L1 4.7µH VFB SW UPS120 22pF VIN 5V TO 8.4V COUT 47µF VOUT 3.3V 1A 174k 3772B TA02a L1: SUMIDA CR43-4R7 CIN: MURATA GRM32ER61C226KA65B COUT: MURATA GRM32ER60J476ME20B Efficiency vs Load Current 100 VIN = 5.5V 90 EFFICIENCY (%) VIN = 7.2V 80 VIN = 8.4V 70 60 50 40 1 10 100 1000 LOAD CURRENT (mA) 10000 3772B TA02b Start-Up Load Step VOUT 2V/DIV VOUT 100mV/DIV (AC) ITH/RUN 1V/DIV IL 500mA/DIV IL 1A/DIV ILOAD 500mA/DIV VIN = 5.5V VOUT = 3.3V RLOAD = 3Ω 400µs/DIV 3772B TA02c 20µs/DIV VIN = 5.5V VOUT = 3.3V ILOAD = 40mA TO 500mA 3772B TA02d 3772bfa 15 LTC3772B U TYPICAL APPLICATIO S 550kHz Micropower 3A Step-Down DC/DC Converter 220pF 34.8k ITH/RUN VIN CIN 22µF LTC3772B GND PGATE IPRG 82.5k VFB NTMS5PO2R2 L1 2.2µH SW COUT 100µF ×2 B320A 22pF VIN 2.75V TO 9.8V 174k VOUT 2.5V 3A 3772B TA03a L1: VISHAY IHLP-2525CZ-01 CIN: GRM32ER61A220KA65B COUT: TAIYO YUDEN LDK375BJ107MM Efficiency vs Load Current 100 90 EFFICIENCY (%) VIN = 3.3V 80 VIN = 5V 70 60 50 40 1 100 1000 10 LOAD CURRENT (mA) 10000 3772B TA03b Start-Up Load Step VOUT 2V/DIV VOUT 100mV/DIV (AC) ITH/RUN 1V/DIV IL 2A/DIV IL 2A/DIV ILOAD 2A/DIV CITH = 220pF RITH = 34.8k RLOAD = 1.5Ω 400µs/DIV 3772B TA03c VIN = 5V 20µs/DIV VOUT = 2.5V ILOAD = 15OmA TO 2A 3772B TA03d 3772bfa 16 LTC3772B U TYPICAL APPLICATIO S 550kHz Micropower 5VIN to 1.8VOUT at 8A DC/DC Converter 470pF 15k ITH/RUN VIN CIN 22µF LTC3772B GND 140k VIN PGATE IPRG VFB Si9433DBY ×2 L1 1µH SW CSHD10-45L 22pF 174k VIN 5V COUT 100µF ×2 VOUT 1.8V 8A 3772B TA04a L1: TOKO FDV0630-1R0 CIN: MURATA GRM32ER61C226K COUT: MURATA GRM32ER60J107K Efficiency vs Load Current 100 EFFICIENCY (%) 90 80 70 60 50 40 100 1000 LOAD CURRENT (mA) 10000 3772B TA04b Start-Up Load Step VOUT 1V/DIV VOUT 200mV/DIV AC COUPLED ITH/RUN 1V/DIV IL 10A/DIV IL 5A/DIV ILOAD 10A/DIV VIN = 5V VOUT = 1.8V RLOAD = 0.25Ω 500µs/DIV 3772B TA04c VIN = 5V 20µs/DIV VOUT = 1.8V ILOAD = 800mA TO 8A 3772B TA04d 3772bfa 17 LTC3772B U PACKAGE DESCRIPTIO DDB Package 8-Lead Plastic DFN (3mm × 2mm) (Reference LTC DWG # 05-08-1702) 0.61 ±0.05 (2 SIDES) 3.00 ±0.10 (2 SIDES) R = 0.115 TYP 5 R = 0.05 TYP 0.40 ± 0.10 8 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) PIN 1 BAR TOP MARK (SEE NOTE 6) 0.200 REF RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 2.00 ±0.10 (2 SIDES) 0.56 ± 0.05 (2 SIDES) 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 3772bfa 18 LTC3772B U PACKAGE DESCRIPTIO TS8 Package 8-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1637) 0.52 MAX 2.90 BSC (NOTE 4) 0.65 REF 1.22 REF 1.4 MIN 3.85 MAX 2.62 REF 2.80 BSC 1.50 – 1.75 (NOTE 4) PIN ONE ID RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 0.22 – 0.36 8 PLCS (NOTE 3) 0.65 BSC 0.80 – 0.90 0.20 BSC 0.01 – 0.10 1.00 MAX DATUM ‘A’ 0.30 – 0.50 REF 0.09 – 0.20 (NOTE 3) 1.95 BSC TS8 TSOT-23 0802 NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3. DIMENSIONS ARE INCLUSIVE OF PLATING 4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR 5. MOLD FLASH SHALL NOT EXCEED 0.254mm 6. JEDEC PACKAGE REFERENCE IS MO-193 3772bfa 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. 19 LTC3772B U TYPICAL APPLICATIO 220pF 15k VIN ITH/RUN CIN 22µF LTC3772B GND 82.5k PGATE IPRG VFB FDC638P L1 3.3µH SW B220A 22pF VIN 3V TO 8V COUT 47µF VOUT 2.5V 2A 174k 3772B F05 L1: TOKO D53LC #A915AY-3R3M CIN: TAIYO YUDEN LMK316BJ226ML COUT: TAIYO YUDEN JMK325BJ476MM Figure 5. 550kHz Micropower Step-Down DC/DC Converter RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC1624 High Efficiency SO-8 N-Channel Switching Regulator Controller N-Channel Drive, 3.5V ≤ VIN ≤ 36V TM LTC1625 No RSENSE Synchronous Step-Down Regulator 97% Efficiency, No Sense Resistor LTC1772/LTC1772B 550kHz ThinSOT Step-Down DC/DC Controllers 2.5V ≤ VIN ≤ 9.8V, VOUT ≥ 0.8V, IOUT ≤ 6A LTC1778/LTC1778-1 No RSENSE Current Mode Synchronous Step-Down Controllers 4V ≤ VIN ≤ 36V, 0.8V ≤ VOUT ≤ (0.9)(VIN), IOUT Up to 20A LTC1872/LTC1872B 550kHz ThinSOT Step-Up DC/DC Controllers 2.5V ≤ VIN ≤ 9.8V; 90% Efficiency LTC3411/LTC3412 1.25A/2.5A, 4MHz Monolithic Synchronous Step-Down Converter 95% Efficiency, 2.5V ≤ VIN ≤ 5.5V, VOUT ≥ 0.8V, TSSOP16 Exposed Pad Package LTC3414 4A, 4MHz Monolithic Synchronous Step-Down Converter 95% Efficiency, 2.5V ≤ VIN ≤ 5.5V, VOUT ≥ 0.8V, TSSOP20 Exposed Pad Package LTC3418 8A, 4MHz Monolithic Synchronous Step-Down Converter 95% Efficiency, 2.5V ≤ VIN ≤ 5.5V, VOUT ≥ 0.8V, TSSOP20 Exposed Pad Package LTC3440 600mA (IOUT), 2MHz Synchronous Buck-Boost DC/DC Converter 2.5V ≤ VIN ≤ 5.5V, Single Inductor LTC3736/LTC3736-2 Dual, 2-Phase, No RSENSE Synchronous Controller with Output Tracking VIN: 2.75V to 9.8V, IOUT Up to 5A, 4mm × 4mm QFN Package LTC3736-1 Dual, 2-Phase, No RSENSE Synchronous Controller with Spread Spectrum VIN: 2.75V to 9.8V, Spread Spectrum Operation, Output Voltage Tracking, 4mm × 4mm QFN Package LTC3737 Dual, 2-Phase, No RSENSE Controller with Output Tracking VIN: 2.75V to 9.8V, IOUT Up to 5A, 4mm × 4mm QFN Package LTC3772 Micropower No RSENSE Constant Frequency Controller VIN: 2.75V to 9.8V, IOUT Up to 5A, ThinSOT, 3mm × 2mm DFN Package LTC3776 Dual, 2-Phase, No RSENSE Synchronous Controller for DDR/QDR Memory Termination Provides VDDQ and VTT with one IC, 2.75V ≤ VIN ≤ 9.8V, Adjustable Constant Frequency with PLL Up to 850kHz, Spread Spectrum Operation, 4mm × 4mm QFN and 16-Lead SSOP Packages LTC3808 No RSENSE, Low EMI, Synchronous Step-Down Controller with Output Tracking 2.75V ≤ VIN ≤ 9.8V, Spread Spectrum Operation, 3mm × 4mm DFN and 16-Lead SSOP Packages LTC3809/LTC3809-1 No RSENSE, Synchronous Step-Down Controller 2.75V ≤ VIN ≤ 9.8V, 3mm × 4mm DFN and 10-Lead MSOP Packages 3772bfa 20 Linear Technology Corporation LT 0606 REV A • PRINTED IN THE USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2005