QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1271 HIGH EFFICIENCY, SMALL FOOTPRINT, STEP-DOWN DC-DC CONVERTER LTC3854EDDB DESCRIPTION Demonstration circuit 1271 is a high efficiency, small footprint, step-down DC-DC converter featuring the LTC3854EDDB. Its output supplies 1.5V @ 15A and its input voltage range is 4.5V to 14V. The demo board uses a high density, two sided drop-in layout with a minimal amount of components. The power components, excluding the bulk output capacitors and bulk input capacitors, fit within a 1.38” X 0.56” area on the top layer. The control circuit on the bottom layer fits within a 0.44” X 0.50” area. Table 1. This demo board provides the user with a simple, low parts count solution for a high output, low output voltage current buck converter. The LTC3854 operates at a switching frequency of 400kHz and CCM at light load. Design files for this circuit board are available. Call the LTC factory. Performance Summary (TA = 25°C) PARAMETER CONDITION VALUE Minimum Input Voltage 4.5V Maximum Input Voltage 14V Output Voltage VOUT VIN = 4.5V to 14V, IOUT = 0A to 15A Maximum Output Current 1.5V ±2% 15A Typical Output Ripple VOUT VIN = 12V, IOUT = 15A (20MHz BW) Nominal Switching Frequency 15mVP–P 400kHz Efficiency (see Figure 3 for efficiency curves) VIN = 12V, IOUT = 15A 86.9% typical QUICK START PROCEDURE Demonstration circuit 1271 is easy to set up to evaluate the performance of the LTC3854EDDB. Refer to Figure 1 for proper measurement equipment setup and follow the procedure below: 1) Place RUN pin jumper in the ON position. 2) With power off, connect the input power supply between VIN and GND. 3) Turn on the power at the input. 4) Check for the proper VOUT = 1.47V to 1.53V output voltages. 5) 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. NOTE: When measuring the output voltage ripple, care must be taken to avoid a long ground lead on the oscilloscope probe. See Figure 2 for proper scope probe technique. Short, stiff leads should be soldered to the (+) and (-) terminals of an output capacitor. The probe’s ground ring needs to touch the (-) lead and the probe tip needs to touch the (+) lead. 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1271 HIGH EFFICIENCY, SMALL FOOTPRINT, STEP-DOWN DC-DC CONVERTER A A Iin Vin V Vin supply Iout Load V Vout Figure 1. Proper Measurement Equipment Setup + COUT VOUT - GND Figure 2. Measuring Input or Output Ripple 2 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1271 HIGH EFFICIENCY, SMALL FOOTPRINT, STEP-DOWN DC-DC CONVERTER 1.5V/15A LTC3854EDDB converter 95% Efficiency 90% 85% Qtop = RJK0305DPB Qbottom = RJK0330DPB L = Toko FDA1055-R56M Rsense = 2mOhms Fsw = 400kHz Mode = CCM Design optimized for a 12V input 80% 75% 70% 0 2 4 6 8 10 12 14 16 Load current (Amps) Vin = 12V Vin = 5V Figure 3. Typical Efficiency Curves 3 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1271 HIGH EFFICIENCY, SMALL FOOTPRINT, STEP-DOWN DC-DC CONVERTER 4