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, This demo board provides the user with a simple, small footprint, step-down DC-DC converter fea- low parts count solution for a high output, low out- turing the LTC3854EDDB. Its output supplies 1.5V put voltage current buck converter. The LTC3854 15A and its input voltage range is 4.5V to 14V. operates at a switching frequency of 400kHz and The demo board uses a high density, two sided CCM at light load. drop-in layout with a minimal amount of compo- Design files for this circuit board are available. nents. The power components, excluding the bulk Call the LTC factory. 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. Performance Summary (T = 25C) A PARAMETER CONDITION VALUE Minimum Input Voltage 4.5V Maximum Input Voltage 14V Output Voltage V V = 4.5V to 14V, I = 0A to 15A 1.5V 2% OUT IN OUT Maximum Output Current 15A Typical Output Ripple V V = 12V, I = 15A (20MHz BW) 15mV OUT IN OUT PP Nominal Switching Frequency 400kHz Efficiency (see Figure 3 for efficiency curves) V = 12V, I = 15A 86.9% typical IN OUT QUICK START PROCEDURE Demonstration circuit 1271 is easy to set up to 5) Once the proper output voltages are estab- evaluate the performance of the LTC3854EDDB. lished, adjust the loads within the operating Refer to Figure 1 for proper measurement equip- range and observe the output voltage regula- ment setup and follow the procedure below: tion, ripple voltage, efficiency and other pa- rameters. 1) Place RUN pin jumper in the ON position. NOTE: When measuring the output voltage ripple, 2) With power off, connect the input power supply care must be taken to avoid a long ground lead on between VIN and GND. the oscilloscope probe. See Figure 2 for proper 3) Turn on the power at the input. scope probe technique. Short, stiff leads should be soldered to the (+) and (-) terminals of an out- 4) Check for the proper output voltages. put capacitor. The probes ground ring needs to V = 1.47V to 1.53V OUT 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 Vout V Iout Load supply Figure 1. Proper Measurement Equipment Setup + - COUT VOUT GND Figure 2. Measuring Input or Output Ripple 2