LTC3544BEUD#PBF

LTC3544B Quad Synchronous Step-Down Regulator: 2.25MHz, 300mA, 200mA, 200mA, 100mA Features Description 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 ■ Low Dropout Operation: 100% Duty Cycle ■ Pulse Skipping at Low Load for Minimum Ripple ■ 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. 3. Keep C8 and C9 as close to the part as possible. 4. Keep the switching nodes (SWx) away from the sensitive VFBx nodes. PC Board Layout Checklist 5. Keep the ground connected plates of the input and output capacitors as close as possible. When laying out the printed circuit board, the following checklist should be used to ensure proper operation of the LTC3544B. These items are also illustrated graphically in Figures 3 and 4. Check the following in your layout: 6. Care should be taken to provide enough space between unshielded inductors in order to minimize any transformer coupling. 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. VCC 2.25V TO 5.5V L4 VOUT1 R15 C15 R16 RUN100 C13 SW1000 RUN200A VOUT3 R5 VFB100 SW200B R6 R8 C10 LTC3544B VFB300 VFB300 RUN300 RUN200B PGND PVIN RUN300 RUN200B SW300 C9 SW300 L1 VOUT4 VFB200A L3 VOUT2 VFB200A VFB200B SW200A SW200B C6 GNDA RUN200A SW200A C4 VCC RUN100 VFB100 L2 GNDA C8 C12 R2 PGND C3 C1 PVIN 2.25V TO 5.5V R3 VFB200B 3544B F03 R11 Figure 3. LTC3544B Layout Diagram 3544bfb 13 LTC3544B Applications information C1 C4 GND L1 L4 C10 VCC C9 L2 L3 C2 C3 PGND 3544B F04 Figure 4 Design Example As a design example, consider using the LTC3544B 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. 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: L4 = 2.5V  2.5V  1– = 4.5µH 2.25MHz • 100mA  4.2V  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 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 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: V  R8 =  OUT – 1 • R7 = 163.2k  0.8  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. Figure 5 shows the complete schematic for this example, along with the efficiency curve and transient response for the 300mA channel. 3544bfb 14 LTC3544B Applications information VSUPPLY 3.6V C10 4.7µF C9 4.7µF L2 4.7µH VOUT2 1.5V C2 4.7µF R3 93.1k C6 20pF C3 4.7µF 4 1 R4 107k R5 0Ω RUN200B 15 7 VCC PVIN RUN100 SW200B SW100 VFB200B VFB100 12 13 L1 10µH C5 20pF 11 C7 20pF 3 5 2 R6 100k RUN200A RUN300 SW200A SW300 VFB200A GNDA GNDA 17 14 PGND VFB300 R1 59k R2 118k LTC3544B L3 4.7µH VOUT3 0.8V 16 9 8 10 L4 4.7µH C8 20pF R7 162k R8 76.8k 6 VOUT1 1.2V C1 4.7µF VOUT2 2.5V C4 4.7µF 3544B F05a Figure 5 Efficiency vs Output Current—300mA Channel, All Other Channels Off Transient Response 100 VOUT = 2.5V 90 TA = 25°C VOUT300 100mV/DIV AC-COUPLED EFFICIENCY (%) 80 70 IL 250mA/DIV 60 50 40 ILOAD 250mA/DIV 30 20 10 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 3544bfb 15 LTC3544B Package Description UD Package 16-Lead Plastic QFN (3mm × 3mm) (Reference LTC DWG # 05-08-1691) 0.70 p0.05 3.50 p 0.05 1.45 p 0.05 2.10 p 0.05 (4 SIDES) PACKAGE OUTLINE 0.25 p0.05 0.50 BSC RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 3.00 p 0.10 (4 SIDES) BOTTOM VIEW—EXPOSED PAD PIN 1 NOTCH R = 0.20 TYP OR 0.25 s 45o CHAMFER R = 0.115 TYP 0.75 p 0.05 15 PIN 1 TOP MARK (NOTE 6) 16 0.40 p 0.10 1 1.45 p 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 p 0.05 0.50 BSC 3544bfb 16 LTC3544B Revision History (Revision history begins at Rev B) REV DATE DESCRIPTION PAGE NUMBER B 5/10 Changes to Order Information Section 2 Pin 14 and Pin 17 Paragraphs Combined in Pin Functions 7 Updates to Functional Diagrams 8 Updated Related Parts 18 3544bfb 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 LTC3544B Related Parts PART NUMBER DESCRIPTION COMMENTS LTC3544 Quad 100mA/200mA/200mA/300mA, 2.25MHz Synchronous Step-Down DC/DC Converter 95% Efficiency, VIN(MIN): 2.3V to 5.5V, VOUT(MIN) = 0.8V, IQ = 70µA, ISD < 1µA, 3mm × 3mm QFN-16 Package LTC3545/ LTC3545-1 Triple, 800mA ×3, 2.25MHz Synchronous Step-Down DC/DC Converter 95% Efficiency, VIN(MIN): 2.3V to 5.5V, VOUT(MIN) = 0.6V, IQ = 58µA, ISD < 1µA, 3mm × 3mm QFN-16 Package LTC3562 Quad, I2C Interface, 600mA/600mA/400mA/400mA, 2.25MHz Synchronous Step-Down DC/DC Converter 95% Efficiency, VIN(MIN): 2.9V to 5.5V, VOUT(MIN) = 0.425V, IQ = 100µA, ISD < 1µA, 3mm × 3mm QFN-20 Package LTC3547/ LTC3547B Dual 300mA, 2.25MHz, Synchronous Step-Down DC/DC Converter 95% Efficiency, VIN(MIN): 2.5V to 5.5V, VOUT(MIN) = 0.6V, IQ = 40µA, ISD < 1µA, DFN-8 Package LTC3417A-2 Dual 1.5A/1A, 4MHz, Synchronous Step-Down DC/DC Converter 95% Efficiency, VIN(MIN): 2.3V to 5.5V, VOUT(MIN) = 0.8V, IQ = 125µA, ISD < 1µA, TSSOP-16E, 3mm × 5mm DFN-16 Packages LTC3407A/ LTC3407A-2 Dual 600mA/600mA 1.5MHz, Synchronous Step-Down DC/DC Converter 95% Efficiency, VIN(MIN): 2.5V to 5.5V, VOUT(MIN) = 0.6V, IQ = 40µA, ISD < 1µA, MS10E, 3mm × 3mm DFN-10 Packages LTC3419/ LTC3419-1 Dual 600mA/600mA 2.25MHz, Synchronous Step-Down DC/DC Converter 95% Efficiency, VIN(MIN): 2.5V to 5.5V, VOUT(MIN) = 0.6V, IQ = 35µA, ISD < 1µA, MS10, 3mm × 3mm DFN-10 Packages LTC3548/ LTC3548-1/ LTC3548-2 Dual 400mA and 800mA IOUT, 2.25MHz, Synchronous StepDown DC/DC Converter 95% Efficiency, VIN(MIN): 2.5V to 5.5V, VOUT(MIN) = 0.6V, IQ = 40µA, ISD < 1µA, MS10E, 3mm × 3mm DFN-10 Packages 3544bfb 18 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com LT 0510 REV B • PRINTED IN USA  LINEAR TECHNOLOGY CORPORATION 2007