DEMO CIRCUIT 1106 QUICK STARTLT3570 GUIDE LT3570 1.5A Buck Converter, 1.5A Boost Converter, and LDO Controller DESCRIPTION Demonstration circuit 1106 is a 1.5A Buck Converter, 1.5A Boost Converter, and LDO Controller featuring the LT3570. The Buck is designed to convert a 4V to 36V source to 3.3V at 1A. The LDO is powered from the output of the Buck and converts it to 2.5V at 100mA. The Boost converts a 3.3V-10V source to 12V at 275mA. DC1106 was designed to switch at 500KHz. In the DC1106 default setting, the Buck and Boost converters run from separate sources to allow for full input variation for the Buck. To facilitate other input options, there are two placeholders on the back of the board, R1 and R2. Installing a jumper at R1, allows the Boost output to power the Buck. Installing a jumper at R2, allows both, the Boost and the Buck to be powered from the same source. The LT3570 features programmable switching frequency, synchronization, external compensation, independent soft-start for each converter. This circuit is intended for space-conscious applications such as Cable Satellite Settop Boxes, Automotive Systems, Telecom Systems “Dying Gasp” Systems and TFT LCD Displays. The LT3570 datasheet gives a complete description of the part, operation and application information. The datasheet must be read in conjunction with this quick start guide for working on or modifying the demo circuit 1106. Design files for this circuit board are available. Call the LTC factory. L, LTC, LTM, LT are registered trademarks of Linear Technology Corporation. Since the input to the Buck powers the internal oscillator, it needs to be on for the Boost to switch. PERFORMANCE SUMMARY FOR DC1106A Specifications are at TA = 25°C SYMBOL VIN BUCK VIN BOOST VOUT BUCK VOUT BOOST VOUT LDO 3.3V RIPPLE 12V RIPPLE 2.5V RIPPLE EFFICIENCY PARAMETER Input Supply Range Input Supply Range Output Voltage Range Output Voltage Range Output Voltage Range CONDITIONS VIN = 4V-36V, ILOAD = 1A VIN = 3.3V-10V, ILOAD = 275mA ILOAD = 100mA VIN =4V, ILOAD = 1A VIN = 12V, ILOAD = 275mA ILOAD = 100mA Both input sources at 5V, Loads: 3.3V = 1A, 12V = 275mA, 2.5V = 100mA MIN 4 3.3 3.2 11.64 2.425 TYP 3.3 12 2.5 20 150 10 87 MAX 36 10 3.4 12.36 2.575 UNITS V V V V V mV mV mV % 1 LT3570 QUICK START PROCEDURE Demonstration circuit 1106 is easy to set up to evaluate the performance of the LT3570. Refer to Figure 1 for proper measurement equipment setup and follow the procedure below: NOTE. When measuring the input or output voltage ripple, care must be taken to avoid a long ground lead on the oscilloscope probe. Measure the input or output voltage ripple by touching the probe tip directly across the Vin or Vout and GND terminals. See Figure 2 for proper scope probe technique. 1. Place jumpers in the following positions: JP1, JP2, JP3 On 2. With power off, connect the input power supplies to Vin and GND. 3. Turn on the power at the input. Check for the proper output voltages. 3.3V = 3.2 to 3.4, 12Vout = 11.64V to 12.36V, and 2.5V = 2.425V to 2.575V. NOTE. If there is no output, temporarily disconnect the load to make sure that the load is not set too high. 4. Once the proper output voltages are established, adjust the loads within the operating range and observe the output voltage regulation, ripple voltage, efficiency and other parameters. 2 LT3570 Figure 1. Proper Measurement Equipment Setup GND VIN Figure 2. Measuring Input or Output Ripple 3 C1 2.2uF X7R 50V C4 10uF 16V [1] DO NOT STUFF. ON 2.5V 1 ON 3.3V 1 ON 12V 1 R3 143K 1% NOTES: UNLESS OTHERWISE SPECIFIED, 1uF C12 C2 4.7uF 16V VIN_BOOST VIN_BUCK TP11 TP5 TP3 TP1 TP4 TP8 SYNC GND 12V@275mA GND 3.3V - 10V VIN BOOST GND 4V - 36V OFF 3 JP3 OFF R11 100K OPT C14 100K R9 100K JP2 3 R12 R7 100K DFLS120 2 R15 22K R2 OPT [1] R1 OPT [1] 100nF C9 SYNC SHDN3 SHDN2 SHDN1 FB1 SW1 1nF C8 14 13 12 11 10 4 U1 LT3570EUF OFF 3 JP1 R4 10K 1% 1 D2 CDRH6D28NP-100 10uH L1 7 IN1 VC1 9 TP2 2 FB2 SW2 BOOST 18 20 21 19 3 24 CHECKED 05/10/06 DATE OPT DFLS140 1 D3 2 TP6 GND SCALE: NONE DWG NO SHEET DC1106A 1 OF 1 REV 2 APPROVED 2.5V@100mA 1630 McCarthy Blvd. Milpitas, CA 95035 Phone: (408)432-1900 Fax: (408)434-0507 1uF TP9 2.2uF TP7 C15 TECHNOLOGY 3.3V@1A 1uF TP10 GND C11 DATE 05/14/08 C6 Q1 FMMT618 FILENAME: 1106A-2.DSN SIZE CAGE CODE Custom 1 PROTO C5 22uF 6.3V REVISION HISTORY DESCRIPTION SCH, LT3570EUF, DC/DC BOOST, BUCK AND LDO CONVERTER 10.2K 1% R10 R8 22.1K 1% TITLE R6 10.2K 1% C13 L2 10uH 2 REV CDRH6D28NP-100 ECO R5 32.4K 1% 100nF Monday, August 04, 2008 DESIGNER ENGINEER APPROVED APPROVALS DRAWN MEI DO NOT SCALE DRAWING R14 22K 1nF C7 C3 CMDSH-3 D1 CONTRACT NO. R13 44.2K 1% VC2 FB3 NP_DRIVE R16 0 VIN_BUCK THIRD ANGLE PROJECTION 100nF C10 22 UNLESS OTHERWISE SPECIFIED DIMENSIONS ARE IN INCHES TOLERANCE ON ANGLE - - 2 PLACES - - - 3 PLACES - - INTERPRET DIM AND TOL PER ASME Y 14.5M -1994 SS1 8 1 IN2 SS2 17 IN2 GND 5 2 1 VIN BUCK GND 6 23 BIAS RT IN3 GND 16 2 2 2 GND 25 Figure 3. Schematic 15 3 4 2 This circuit is proprietary to Linear Technology and s upplied for use with Linear Technology parts . Customer Notice:Linear Technology has m ade a bes t effort to design a circuit that m eets custom er-s upplied s pecifications; however, it rem ains the cus tom er's respons ibility to verify proper and reliable operation in the actual application, Com ponent s ubs titution and printed circuit board layout m ay s ignificantly affect circuit perform ance or reliability. Contact Linear Applications Engineering for ass is tance. LT3570