QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 755 600KHZ, 1A SYNCHRONOUS BUCK-BOOST CONVERTER LTC3443 DESCRIPTION Demonstration Circuit 755 is a constant-frequency synchronous Buck-Boost converter using the LTC3443. The input range is from 2.4V to 5.5V, making it ideal for single-cell lithium-ion or threecell 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 600kHz, which is a good trade-off between efficiency and size. Applying twice the desired Table 1. frequency at the MODE/SYNC pin can also synchronize the switching frequency between 690kHz to 1.2MHz. In shutdown, the IC draws less than 1A. When using long wire connection to the input sources (such as wall adaptors), there can be input over voltage transients during initial plug-in. C8 is installed on DC755 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. 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 5.5V, IOUT = 0A to 1A 3.3V 4% Maximum Output Current VIN = 2.5V 1A 12mVPP (measured at C5) Typical Output Ripple VOUT VIN = 3.0V, IOUT = 1A (20MHz BW) Typical Switching Frequency Efficiency (Fixed Frequency Mode) 30mVPP (measured across TP1 and TP2) 600kHz VIN = 4.2V, IOUT = 0.2A 95% Typical VIN = 4.2V, IOUT = 1A 91% Typical Off (40C to 85C) 0.4V MAX On (-40C to 85C) 1.4V MIN On/Off Control 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 755 600KHZ, 1A SYNCHRONOUS BUCK-BOOST CONVERTER QUICK START PROCEDURE Demonstration circuit 755 is easy to set up to evaluate the performance of the LTC3443. 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: 2. With power off, connect the input power supply to Vin and GND. 3. Turn on the power at the input. NOTE: Make sure that the input voltage does not exceed 5.5V. 4. Check for the proper output voltage. Vout = 3.17V to 3.43V. NOTE: If there is no output, temporarily disconnect the load to make sure that the load is not set too high. 5. Once the proper output voltage is established, JP1 RUN JP2 FIXED FREQ. adjust the load within the operating range and observe the output voltage regulation, ripple voltage, efficiency and other parameters. 2 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 755 600KHZ, 1A SYNCHRONOUS BUCK-BOOST CONVERTER GRAPHICS Figure 1. Proper Measurement Equipment Setup 3 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 755 600KHZ, 1A SYNCHRONOUS BUCK-BOOST CONVERTER GND VIN Figure 2. Measuring Input or Output Ripple Efficiency vs. Load 100% 90% Efficiency% 80% 2.7Vin PWM 70% 3.6Vin PWM 60% 4.2Vin PWM 50% 2.7Vin Burst 40% 3.6Vin Burst 30% 4.2Vin Burst 20% 10% 0% 0.1 1 10 100 1000 Iout (mA) Figure 3. Efficiency of DC755 4 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 755 600KHZ, 1A SYNCHRONOUS BUCK-BOOST CONVERTER Figure 4. Load Transient Response (Vin=3.3V; Channel 1: Vout, 100mV/div; Channel4: Iout load step: 100mA to 1A) 5 5 4 3 2 1 D D 4 5 SW1 9 10 C SW2 PVIN VOUT 8 VIN 1 SHDN/SS FB 12 7 MODE/SYNC VC 11 C PGNDPGND GND 3 6 2 B B A A 5 4 3 2 1 Bill Of Material Demo Bd. #755A Linear Technology Corporation LTC3443EDE 6/20/2005 Item Qty Reference 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 22 1 1 1 0 1 1 1 1 0 2 1 2 2 1 1 1 1 1 1 0 1 C1 C2 C3 C4 (Opt) C5 C6 C7 C8 C9 (Opt) D2,D1 D3 JP1,JP2 XJP1-XJP2 L1 R1 R2 R3 R4 R6 R7 (Opt) U1 Part Description Cap., X5R 10uF 6.3V 20% Cap., X5R 0.047uF 16V 20% Cap., X7R 560pF 16V 20% Cap., NPO 10pF 25V 10% Cap., X5R 47uF 6.3V 20% Cap., X5R 1uF 6.3V 10% Cap., NPO 150pF 25V 5% Cap., Tant. 47uF 10V 20% Cap., X7R 1000pF 25V 20% Schottky Diodes, 1A/20V Schottky Diodes, 1A/20V Headers, 3 Pins 2mm Ctrs. SHUNT, .079" CENTER Inductor, 6.0uH Res., Chip 1.0M 1/16W 5% Res., Chip 15K 1/16W 5% Res., Chip 200K 0.06W 1% Res., Chip 340K 1/16W 1% Res., Chip 2.2K 0.06W 5% Res., Chip 2.0 0.06W 1% I.C., Buck Converter Page 1 - of - 1 Manufacture / Part # Taiyo Yuden JMK212BJ106MG-T AVX 0402YD473MAT2A AVX 0402YC561MAT2A AVX 04023A100KAT2A Taiyo Yuden JMK325BJ476MM-T Taiyo Yuden JMK107BJ105KA-T AVX 04023A151JAT2A AVX TAJB476M010 AVX 04023C102MAT2A Philips PMEG2010EA ON SEMI. MBRM120ET3 CommConn Con Inc. 2802S-03G2 COMM-CON CCIJ2MM-138GW Sumida CDRH6D28-6R0NC AAC CR05-105JM AAC CR05-153JM AAC CR05-2003FM AAC CR05-3403FM AAC CR05-222JM AAC CR05-2R00FM Linear Tech. Corp. LTC3443EDE