QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 625 1MHZ, 1A SYNCHRONOUS BUCK-BOOST CONVERTER LTC3441 DESCRIPTION Demonstration Circuit 625 is a constant-frequency synchronous Buck-Boost converter using the LTC3441. The input range is from 2.4V to 5.5V, making it ideal for single-cell lithium-ion or three-cell NiCd/NiMH battery applications. This converter provides up to 95% efficiency, much higher than traditional Buck-Boost converters. For 2.5V minimum input voltage, this converter can provide up to 1A load current. The output voltage is set at 3.3V. A different output voltage in the range of 2.4V to 5.25V can be obtained by changing one of the feedback resistors. The switching frequency is set at 1MHz, which is a good trade-off between efficiency and size. Applying twice the desired frequency at the MODE/SYNC pin can also synchronize the switching frequency between 1.15MHz to 1.7MHz. In shutdown, the IC draws less than 1A. When using long wire connections to the input sources (such as wall adaptors), there can be input over voltage transients during initial plug-in. C8 is installed on DC625 to damp the possible voltage transients. C8 is not needed for any application when input source is close to the regulator. Please refer to Application Note 88 for details. Design files for this circuit board are available. Call the LTC factory. Table 1. Performance Summary (TA = 25C unless otherwise noted) PARAMETER CONDITION VALUE Minimum Input Voltage -40C to 85C 2.4V (2.5V minimum input for 1A load) Maximum Input Voltage -40C to 85C 5.5V Output Voltage VOUT VIN = 2.5V to 5.25V, IOUT = 0A to 1A 3.3V 3% Maximum Output Current VIN = 2.5V to 5.25V 1A Typical Output Ripple VOUT VIN = 3.0V, IOUT = 1A (20MHz BW) 40mVP-P Typical Switching Frequency Efficiency 1MHz VIN = 4.2V, IOUT = 0.2A 94% Typical VIN = 4.2V, IOUT = 1A 89% Typical Logic Low Voltage-Off, -40C to 85C 0.4V MAX Logic High Voltage-On 2.4V MIN On/Off Control QUICK START PROCEDURE Demonstration circuit 625 is easy to set up to evaluate the performance of the LTC3441. 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 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 625 1MHZ, 1A SYNCHRONOUS BUCK-BOOST CONVERTER or Vout and GND terminals. See Figure 2 for proper scope probe technique. 1. Place jumpers in the following positions: NOTE: Make sure that the input voltage does not exceed 5.5V. 4. Check for the proper output voltage. Vout = 3.2V to 3.4V. JP1 JP2 RUN NOTE: If there is no output, temporarily disconnect the load to make sure that the load is not set too high. FIXED FREQ. 2. With power off, connect the input power supply to Vin and GND. 3. Turn on the power at the input. 5. Once the proper output voltage is established, adjust the load within the operating range and observe the output voltage regulation, ripple voltage, efficiency and other parameters. Figure 1. Proper Measurement Equipment Setup 2 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 625 1MHZ, 1A SYNCHRONOUS BUCK-BOOST CONVERTER GND VIN Figure 2. Measuring Input or Output Ripple GRAPHICS Efficiency% Efficiency vs. Load 100.0% 90.0% 80.0% 70.0% 60.0% 50.0% 40.0% 30.0% 20.0% 10.0% 0.0% 2.7Vin PWM 3.6Vin PWM 4.2Vin PWM 2.7Vin Burst 3.6Vin Burst 4.2Vin Burst 0.1 1 10 100 1000 Iout (mA) Figure 3. Efficiency of DC625 3 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 625 1MHZ, 1A SYNCHRONOUS BUCK-BOOST CONVERTER Figure 4. Load Transient Response (Vin=3V;Channel 1: Vout; Channel 2: Iout: load step from 100mA to 1A) 4 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 625 1MHZ, 1A SYNCHRONOUS BUCK-BOOST CONVERTER 5 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 625 1MHZ, 1A SYNCHRONOUS BUCK-BOOST CONVERTER 6 5 4 3 2 1 D D 9 10 1 4 5 SW1 SW2 PVIN VOUT 8 VIN SHDN/SS FB 12 C C 7 MODE/SYNC VC 11 PGNDPGND GND 3 6 2 B B A A 5 4 3 2 1 Bill Of Material Demo Bd. #625A Linear Technology Corporation LTC3441EDE 6/17/2005 Item Qty Reference 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 1 1 2 0 1 1 1 0 2 2 2 1 1 1 1 1 1 1 0 5 1 4 4 1 2 C1 C2 C3,C7 C4 (Opt) C5 C6 C8 C9 (Opt) D2,D1 JP1,JP2 XJP1,XJP2 L1 R1 R2 R3 R4 R5 R6 R7 (Opt) TP1,TP2,TP3,TP4,TP5 U1 Part Description Cap., X5R 10uF 6.3V 20% Cap., X5R 0.047uF 16V 5% Cap., NPO 220pF 25V 10% Cap., NPO 10pF 25V 10% Cap., X5R 47uF 6.3V 20% Cap., X5R 1uF 6.3V 10% Cap., Tant. 47uF 10V 20% Cap., X7R 1000pF 25V 20% Schottky Diode, 1A / 20V Headers, 3 Pins 2mm Ctrs. Shunt, 2 Pins 2mm Ctrs. Inductor, 3.3uH Res., Chip 1.0M 1/16W 5% Res., Chip 15K 1/16W 5% Res., Chip 200K 0.06W 1% Res., Chip 348K 1/16W 1% Res., Chip 5.1M 1/16W 5% Res., Chip 2.2K 0.06W 5% Res., Chip 2.0 0.06W 1% Turret, Testpoint I.C., Buck Converter SCREW, #4-40, 1/4" STANDOFF, #4-40 1/4" PRINTED CIRCUIT BOARD TOP STENCIL Page 1 - of - 1 Manufacture / Part # Taiyo Yuden JMK212BJ106MG-T AVX 0402YD473JAT AVX 04023A221KAT2A AVX 04023A100KAT2A Taiyo Yuden JMK325BJ476MM-T Taiyo Yuden JMK107BJ105KA-T AVX TAJB476M010 AVX 04023C102MAT2A PHILIPS PMEG2010EA CommConn Con Inc. 2802S-03G2 CommConn Con Inc. CCIJ2MM-138G TOKO A916CY-3R3M AAC CR05-105JM AAC CR05-153JM AAC CR05-2003FM AAC CR05-3483FM AAC CR05-515JM AAC CR05-222JM AAC CR05-2R00FM Mill Max 2501-2 Linear Tech. Corp. LTC3441EDE ANY MICRO PLASTICS 14HTSP101 FAB., DEMO CIRCUIT 625A STENCIL DC625A