DC349B Quick Start Guide DESCRIPTION Demonstration Circuit DC349B demonstrates a synchronous step-up DC/DC converter using the LTC1700 controller. The LTC1700 is a current mode No RSENSETM synchronous step-up controller with up to 95% efficiency. Applications include 2.5V to 3.3V or 5V converters, 2.5V to 5V converters, singlecell Li-Ion to 5V applications or two cell AA to 3.3V or 5V applications. The LTC1700's 550kHz operating frequency allows the use of small inductors and capacitors. The device can also be synchronized to frequencies between 400kHz to 750kHz. Burst ModeTM operation is disabled when the device is synchronized or the SYNC/MODE pin is pulled low to reduce noise. To prevent inductor current runaway, the duty cycle is limited to 90%. Overvoltage protection turns both external MOSFETs off when the output rises about 5% above the regulated value. DC349B provides output voltages of 3.3V or 5V (jumper selectable). QUICK START GUIDE 1. Proper setup is essential for accurate and meaningful evaluation of efficiency and regulation. Figure 1 shows the appropriate arrangement of supply, load, ammeters and voltmeters. Figure 1. DC349B Test and Measurement Setup 2. Apply a voltage source to the input of the circuit between the VIN and GND terminals. The circuit will operate from an input voltage as low as 1.8V. Do not apply more than 4V to the input. 3. Select the appropriate position of jumper JP1 for the output voltage (open for 5V, closed for 3.3V). 4. Refer to Figure 4 in the data sheet to apply an appropriate load current between the VOUT and GND terminals at start-up. 5. The RUN terminal can be left unconnected. To shut down the LTC1700, connect this terminal to GND. 6. Connect the SYNC/MODE terminal to the VIN terminal to enable Burst Mode operation at low load currents or connect it to GND or an external clock to defeat Burst Mode operation. Do not attempt to synchronize to a clock below 400kHz or above 750kHz. PERFORMANCE SUMMARY PARAMETER CONDITION VALUE Maximum Load Current (Min) (Note 1) VIN = 2.5V, VOUT = 3.3V 1A VIN = 2.5V, VOUT = 5.0V 0.7A VIN = 3.3V, VOUT = 5.0V 1A Note 1: This limit is based on the DC349B circuit. The LTC1700 can provide higher output currents. PARTS LIST Item Qty 1 2 3 4 5 6 7 8 9 10 11 12 13 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 1 1 Reference Passive Comp. C1 C2 C3 C4 C6 C7 C8 C9 R1 R2 R3 R4 L1 Active comp. Q1 Q2 Part Description Manufacture / Part # CAP, X5R, 22uF, 6.3V, 20%, 1210 CAP, TANT, 68uF, 6.3V, 10% , 1210 CAP, X5R,10uF, 6.3V, 20%, 1206 CAP, POSCAP, 330uF, 6.3V, 7343 CAP, X7R, 0.1uF, 16V, 10%, 0603 CAP, X7R, 220pF, 25V, 10%, 0603 CAP, X7R, 100pF, 25V, 10%, 0603 CAP, X5R, 4.7uF, 6.3V, 20%, 0805 RES., CHIP 392K 1/16W 1% 0603 RES., CHIP 316K 1/16W 1% 0603 RES., CHIP 2.2K 1/16W 5% 0603 RES., CHIP 100K 1/16W 1% 0603 INDUCTOR, 1.5UH TAIYO YUDEN JMK325BJ226MM-T AVX, TAJB686K006RNJ TAIYO YUDEN JMK316BJ106ML-T PANASONIC 6TPB330M AVX 0603YC104KAT2A AVX 06033C221KAT2A AVX 06033C101KAT2A TAIYO YUDEN JMK212BJ475MG-T VISHAY CRCW0603392KFKEA VISHAY CRCW0603316KFKEA VISHAY CRCW06032K20JNEA VISHAY CRCW0603100KFKEA MURATA LQH66SN1R5M03 P-MOSFET, AO4419, SO-08 N-MOSFET, AO4202, SO-08 ALPHA&OMEGA, AO4419 ALPHA&OMEGA, AO4202 3 1 1 2 3 4 5 6 1 1 2 1 U1 Hardware E1-E6 JP1 JP2 XJP1, XJP2 I.C., LTC1700EMS MSOP10 LINEAR LTC1700EMS#PBF TURRET, 0.079 SINGLE ROW HEADER, 2 pin 0.079 SINGLE ROW HEADER, 3 pin SHUNT, .079" CENTER PRINTED CIRCUIT BOARDS MILL-MAX 2501-2 COMM CON 2802S-02-G1 COMM CON 2802S-03-G1 SAMTEC, 2SN-BK-G DEMO BOARD 349B