DC1171A-B Analog Devices

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1171A SYNCHRONOUS BUCK CONVERTER LTC3851EGN DESCRIPTION Demonstration circuit 1171A is a single output The main features of the board include an internal synchronous buck converter featuring the 5V linear regulator for bias and a Mode selector LTC3851EGN. The circuit is designed with all that allows the converter to run in CCM, pulse skip components on the top side. The package style for or Burst Mode operation (requires some minor the LTC3851EGN is a 16-lead narrow SSOP. modification). Synchronization to an external clock is also possible. Two versions of the board are available. DC- 1171A-A has an on-board sense resistor for cur- The input voltage range is 4.5V to 14V. The rent feedback, while the DC1171A-B is configured LTC3851 datasheet gives a complete description with a DCR sense circuit that allows the converter of the part, operation and application information to use the inductors DCR as the sense element and must be read in conjunction with this quick instead of the on-board sense resistor to save start guide for demo circuit 1171A. cost, board space while improving full load effi- Design files for this circuit board are available. ciency over 2%. Call the LTC factory. Burst Mode is a trademark of Linear Technology Corporation Table 1. Performance Summary (T = 25C) A PARAMETER CONDITION VALUE Input Voltage Range 4.5V - 14V Output Voltage V V = 4.5V to 14V, I = 0A to 15A 1.5V 2% OUT IN OUT Nominal Switching Frequency 400kHz Efficiency 87.3% Typical (A-A) V = 1.5V, I = 15A V = 12V OUT OUT1 IN See Figure 3 and 4 for efficiency curves 90.0% Typical (A-B) QUICK START PROCEDURE Demonstration circuit 1171A is easy to set up to 1. Place jumpers in the following positions: evaluate the performance of the LTC3851EGN. JP1 400k Refer to Figure 1 for proper measurement equip- JP2 On ment setup and follow the procedure below: JP3 CCM NOTE: When measuring the input or output voltage ripple, care must be taken to avoid a long ground 2. With power off, connect the input power supply lead on the oscilloscope probe. Measure the input to Vin and GND. or output voltage ripple by touching the probe tip 3. Turn on the power at the input. directly across the Vin or Vout and GND terminals. See Figure 2 for proper scope probe technique. NOTE: Make sure that the input voltage does not exceed 14V. 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1171A SYNCHRONOUS BUCK CONVERTER 4. Check for the proper output voltage. range and observe the output voltage regula- Vout = 1.470V to 1.530V tion, ripple voltage, efficiency and other parame- NOTE: If there is no output, temporarily discon- ters. nect the load to make sure that the load is not 6. Different operating modes can be evaluated by set too high. changing the position of jumper JP3 and are 5. Once the proper output voltages are estab- discussed in the next section. lished, adjust the loads within the operating Iin A + + V Vin supply - Vin - Vout + - V Iout A Vout + - load Figure 1. Proper Measurement Equipment Setup 2