LTC3544EUD#TRPBF

LTC3544 Quad Synchronous Step-Down Regulator: 2.25MHz, 300mA, 200mA, 200mA, 100mA FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ High Efficiency: Up to 95% Four Independent Regulators Provide Up to 300mA, 200mA, 200mA and 100mA Output Current 2.25V to 5.5V Input Voltage Range 2.25MHz Constant-Frequency Operation No Schottky Diodes Required Extremely Low Channel-to-Channel Transient Crosstalk Low Ripple (20mVP-P) Burst Mode Operation: IQ = 70μA (All Channels On) 0.8V Reference Allows Low Output Voltages Shutdown Mode Draws 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 charging to 3.3V would require a 250μs rise time, limiting the charging current to about 130mA. 3544fa 12 LTC3544 APPLICATIONS INFORMATION PC Board Layout Checklist 3. Keep C8 and C9 as close to the part as possible. When laying out the printed circuit board, the following checklist should be used to ensure proper operation of the LTC3544. These items are also illustrated graphically in Figures 3 and 4. Check the following in your layout: 4. Keep the switching nodes (SWx) away from the sensitive VFBx nodes. 5. Keep the ground connected plates of the input and output capacitors as close as possible. 1. The power traces, consisting of the PGND trace, the GNDA trace, the SW traces, the PVIN trace and the VCC trace should be kept short, direct and wide. 6. Care should be taken to provide enough space between unshielded inductors in order to minimize any transformer coupling. 2. Does each of the VFBx pins connect directly to the respective feedback resistors? The resistive dividers must be connected between the (+) plate of the corresponding output filter capacitor (e.g., C13) and GNDA. If the circuit being powered is at such a distance from the part where voltage drops along circuit traces are large, consider a Kelvin connection from the powered circuit back to the resistive dividers. VCC 2.25V TO 5.5V L4 Design Example As a design example, consider using the LTC3544 as a portable application with a Li-Ion battery. The battery provides VIN ranging from 2.8V to 4.2V. The demand at 2.5V is 250mA necessitating the use of the 300mA output for this requirement. GNDA C8 VOUT1 R15 C15 R16 RUN100 C13 SW1000 VCC GNDA VFB100 C1 VFB200A RUN100 VFB300 VFB100 C4 GND VFB200B VFB300 L1 L4 LTC3544 RUN200A L2 VOUT3 R5 RUN200A SW200A SW200A SW200B C6 SW200B C4 RUN300 RUN200B PGND PVIN RUN300 C9 SW300 C9 L2 L1 VFB200A R8 R2 PGND VOUT2 C3 C2 C3 C1 PVIN 2.25V TO 5.5V C12 L3 VOUT4 R6 L3 C10 VCC RUN200B SW300 PGND R3 VFB200B C10 3544 F04 3544 F03 R11 Figure 3. LTC3544 Layout Diagram Figure 4. LTC3544 Suggested Layout 3544fa 13 LTC3544 APPLICATIONS INFORMATION Beginning with this channel, first calculate the inductor value for about 35% ripple current (100mA in this example) at maximum VIN. Using a form of Equation 1: L4 = 200k are a good compromise between efficiency and immunity to any adverse effects of PCB parasitic capacitance on the feedback pins. Choosing 10μA with 0.8V feedback voltage makes R7 = 80k. A close standard 1% resistor is 76.8k. Using: 2.5V ⎛ 2.5V ⎞ 1– = 4.5µH 2.25MHz • 100mA ⎜⎝ 4.2V ⎟⎠ ⎛V ⎞ R8 = ⎜ OUT – 1⎟ • R7 = 163.2k ⎝ 0.8 ⎠ For the inductor, use the closest standard value of 4.7μH. A 4.7μF capacitor should be sufficient for the output capacitor. A larger output capacitor will attenuate the load transient response, but increase the settling time. A value for CIN = 4.7μF should suffice as the source impedance of a Li-Ion battery is very low. The closest standard 1% resistor is 162k. An optional 20pF feedback capacitor may be used to improve transient response. The component values for the other channels are chosen in a similar fashion. The feedback resistors program the output voltage. Minimizing the current in these resistors will maximize efficiency at very light loads, but totals on the order of Figure 5 shows the complete schematic for this example, along with the efficiency curve and transient response for the 300mA channel. VSUPPLY 3.6V C10 4.7μF C9 4.7μF 15 L2 4.7μH VOUT2 1.5V C2 4.7μF VOUT3 0.8V R3 93.1k 16 4 C6 20pF 1 7 PVIN SW200B RUN100 SW100 VFB200B R4 107k VFB100 12 13 L1 10μH C5 20pF 11 3 5 R6 100k 2 RUN200A RUN300 SW200A SW300 VFB200A VFB300 GNDA 14 VOUT1 1.2V R1 59k C1 4.7μF R2 118k LTC3544 L3 4.7μH C3 4.7μF RUN200B VCC 9 8 10 PGND L4 4.7μH C8 20pF VOUT2 2.5V R7 162k C4 10μF R8 76.8k 6 3544 F05a Figure 5. Design Example Efficiency vs Output Current—300mA Channel, All Other Channels Off Transient Response 100 90 VOUT300 50mV/DIV AC COUPLED 80 EFFICIENCY (%) 70 60 IL 250mA/DIV 50 40 ILOAD 250mA/DIV 30 20 10 VOUT = 2.5V TA = 25°C 0 0.0001 VIN = 2.7V VIN = 3.6V VIN = 4.2V 0.001 0.01 0.1 LOAD CURRENT (A) 1 VIN = 3.6V 20μs/DIV VOUT = 2.5V TA = 25°C LOAD STEP = 300μA TO 300mA 3544B F05c 3544B F05b 3544fa 14 LTC3544 PACKAGE DESCRIPTION UD Package 16-Lead Plastic QFN (3mm × 3mm) (Reference LTC DWG # 05-08-1691) 0.70 ±0.05 3.50 ± 0.05 1.45 ± 0.05 2.10 ± 0.05 (4 SIDES) PACKAGE OUTLINE 0.25 ±0.05 0.50 BSC RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 3.00 ± 0.10 (4 SIDES) BOTTOM VIEW—EXPOSED PAD PIN 1 NOTCH R = 0.20 TYP OR 0.25 × 45° CHAMFER R = 0.115 TYP 0.75 ± 0.05 15 16 PIN 1 TOP MARK (NOTE 6) 0.40 ± 0.10 1 1.45 ± 0.10 (4-SIDES) 2 (UD16) QFN 0904 0.200 REF 0.00 – 0.05 NOTE: 1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WEED-2) 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 0.25 ± 0.05 0.50 BSC 3544fa 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 LTC3544 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC3405/LTC3405A 300mA IOUT, 1.5MHz, Synchronous Step-Down DC/DC Converters 95% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN) = 0.8V, IQ = 20μA, ISD < 1μA, ThinSOTTM Package LTC3406/LTC3406B 600mA IOUT, 1.5MHz, Synchronous Step-Down DC/DC Converters 96% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN) = 0.6V, IQ = 20μA, ISD < 1μA, ThinSOT Package LTC3407/LTC3407-2 Dual 600mA/800mA IOUT, 1.5MHz/2.25MHz, Synchronous Step-Down DC/DC Converters 95% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN) = 0.6V, IQ = 40μA, ISD < 1μA, 10-Lead MSE, DFN Packages LTC3409 600mA IOUT, 1.7MHz/2.6MHz, Synchronous Step-Down DC/DC Converter 96% Efficiency, VIN: 1.6V to 5.5V, VOUT(MIN) = 0.6V, IQ = 65μA, ISD < 1μA, DFN Package LTC3410/LTC3410B 300mA IOUT, 2.25MHz, Synchronous Step-Down DC/DC Converters 95% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN) = 0.8V, IQ = 26μA, ISD < 1μA, SC70 Package LTC3411 1.25A IOUT, 4MHz, Synchronous Step-Down DC/DC Converter 95% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN) = 0.8V, IQ = 60μA, ISD < 1μA, 10-Lead MSE, DFN Packages LTC3412 2.5A IOUT, 4MHz, Synchronous Step-Down DC/DC Converter 95% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN) = 0.8V, IQ = 60μA, ISD < 1μA, 16-Lead TSSOPE Package LTC3441/LTC3442 LTC3443 1.2A IOUT, 2MHz, Synchronous Buck-Boost DC/DC Converters 95% Efficiency, VIN: 2.4V to 5.5V, VOUT(MIN): 2.4V to 5.25V, IQ = 50μA, ISD < 1μA, DFN Package LTC3446 Monolithic Synchronous Buck Regulator with Dual VLDOTM Requlators 92% Efficiency, VIN: 2.7V to 5.5V, VOUT(MIN) = 0.4V, IQ = 140μA, ISD < 1μA, 3mm × 4mm DFN Package LTC3531/LTC3531-3 LTC3531-3.3 200mA IOUT, 1.5MHz, Synchronous Buck-Boost DC/DC Converters 95% Efficiency, VIN: 1.8V to 5.5V, VOUT(MIN): 2V to 5V, IQ = 16μA, ISD < 1μA, ThinSOT, DFN Packages LTC3532 500mA IOUT, 2MHz, Synchronous Buck-Boost DC/DC Converter 95% Efficiency, VIN: 2.4V to 5.5V, VOUT(MIN): 2.4V to 5.25V, IQ = 35μA, ISD < 1μA, 10-Lead MSE, DFN Packages LTC3544B 300mA, 2 × 200mA, 100mA Quad 2.25MHz Synchronous Buck DC/DC Converter 95% Efficiency, VIN: 2.25V to 5.5V, VOUT(MIN) = 0.8V, IQ = 825μA, ISD < 1mA, 3mm × 3mm QFN Package LTC3547/LTC3547B Dual 300mA IOUT, 2.25MHz, Synchronous Step-Down DC/DC Converter 95% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN) = 0.6V, IQ = 40μA, ISD < 1μA, 8-Lead DFN Package LTC3548/LTC3548-1 LTC3548-2 Dual 400mA/800mA IOUT, 2.25MHz, Synchronous Step-Down DC/DC Converters 95% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN) = 0.6V, IQ = 40μA, ISD < 1μA, 10-Lead MSE, DFN Packages LTC3561 1.25A IOUT, 4MHz, Synchronous Step-Down DC/DC Converter 95% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN) = 0.8V, IQ = 240μA, ISD < 1μA, DFN Package ThinSOT and VLDO are trademarks of Linear Technology Corporation 3544fa 16 Linear Technology Corporation LT 0308 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 2007