DEMO CIRCUIT 1432A LTC3851AEUD/ LTC3851AEUD-1 QUICK START GUIDE LTC3851AEUD/ LTC3851AEUD-1 SYNCHRONOUS BUCK CONVERTER DESCRIPTION Demonstration circuit 1432A is a synchronous buck element to save cost, footprint and improve full load effi- converter featuring the LTC3851AEUD/ LTC3851AEUD-1. ciency about 2%. The demo circuit is available in two versions. DC1432A-A The LTC3851AEUD/ LTC3851AEUD-1 datasheet gives a is configured with LTC3851AEUD which provides ISET complete description of these parts, operation and appli- function, while the DC1432A-B is configured with cation information and must be read in conjunction with LTC3851AEUD-1 which provides PGOOD function. this quick start guide for Demonstration circuit 1432A. The main features of the board include an internal 5V Design files for this circuit board are available. Call linear regulator for bias and a Mode selector that allows the LTC factory. the converter to run in Forced CCM Mode, Pulse Skip L, LTC, LTM, LT, Burst Mode, OPTI-LOOP, Over-The-Top and PolyPhase are registered Mode or Burst Mode operation. Synchronization to an trademarks of Linear Technology Corporation. Adaptive Power, C-Load, DirectSense, Easy Drive, FilterCAD, Hot Swap, LinearView, Module, Micropower SwitcherCAD, Multimode external clock is also possible on this board. Dimming, No Latency , No Latency Delta-Sigma, No R , Operational Filter, PanelPro- SENSE tect, PowerPath, PowerSOT, SmartStart, SoftSpan, Stage Shedding, SwitcherCAD, ThinSOT, The demo circuit has an optional DCR sense circuit that UltraFast and VLDO are trademarks of Linear Technology Corporation. Other product names may be trademarks of the companies that manufacture the products. allows using the inductors DCR as the current sensing Table 1. Performance Summary (T =25C) A PARAMETER CONDITIONS MIN TYP MAX UNITS Input Supply Range 4.5 14 V Output Voltage Range V = 12V, I = 15A 1.47 1.5 1.53 V IN LOAD Nominal Switching Frequency 350 kHz Full Load Efficiency V = 12V, V = 1.5V, I = 15A 88.9 % IN OUT LOAD (See Figure 3 for efficiency curves) QUICK START PROCEDURE Demonstration circuit 1432A is easy to set up to evaluate 1. Place jumpers in the following positions: the performance of the LTC3851AEUD/ LTC3851AEUD-1. FREQ/PLLFLTR 350kHz Refer to Figure 1 for proper measurement equipment On RUN setup and follow the procedure below: NOTE. When measuring the input or output voltage ripple, care must be MODE/PLLIN CCM taken to avoid a long ground lead on the oscilloscope probe. Measure the 2. With power off, connect the input power supply to 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 Vin and GND. technique. 3. Turn on the power at the input. NOTE. Make sure that the input voltage does not exceed 14V. 1 GND VIN LTC3851AEUD/ LTC3851AEUD-1 4. Check for the proper output voltage. Vout = 1.470V the output voltage regulation, ripple voltage, efficien- to 1.530V cy and other parameters. NOTE. If there is no output, temporarily disconnect the load to make 6. Different operating modes can be evaluated by sure that the load is not set too high. changing the position of MODE/PLLIN jumper and 5. Once the proper output voltages are established, ad- are discussed in the next section. just the loads within the operating range and observe Iin A + + V Vin supply Vin - - Vout + - V Iout A Vout + - load Figure 1. Proper Measurement Equipment Setup Figure 2. Measuring Input or Output Ripple 2