QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 870A-B HIGH EFFICIENCY MONOLITHIC SYNCHRONOUS BUCK REGULATOR LTC3410B DESCRIPTION Demonstration circuit 870A-B is a high efficiency, high frequency buck converter, incorporating the LTC3410B monolithic synchronous regulator. The DC870 has an input voltage range of 2.25V to 5.5V, and is capable of delivering up to 300 mA of output current. It has an output voltage range from 0.8V to 5V, and an operating frequency range of 2.25 MHz (allowing the exclusive use of low profile surface mount components). In low load current operation, the LTC3410B operates in pulse-skip mode. The DC870 is a very efficient circuit: up to 96%. These features, plus the LTC3410B coming in a tiny, lowprofile 6-Pin SC70 package, make the DC870 demo board an ideal circuit for use in battery-powered, hand-held applications. Design files for this circuit board are available. Call the LTC factory. TM - Burst Mode is a trademark of Linear Technology Corporation Table 1. Performance Summary (TA = 25°C) PARAMETER Minimum Input Voltage CONDITION VALUE 2.25V Maximum Input Voltage Output Voltage VOUT Typical Output Ripple VOUT Output Regulation 5.5V VIN = 2.25V to 5.5V, IOUT = 0A to 0.3A 1.8V ±4% VIN = 5V, IOUT = 0.3A (20 MHz BW) 20mVP–P Line ±1% Load ±1% Nominal Switching Frequency 2.25 MHz QUICK START PROCEDURE The DC870A-B is easy to set up to evaluate the performance of the LTC3410B. For proper measurement equipment configuration, set up the circuit according to the diagram in Figure 1. Before proceeding to test, insert jumper JP1 shunt into the off position, connecting the RUN pin to ground (GND), which shuts down the circuit. 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 out- put 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. Connect the input power supply and the load to the board. Do not hot-plug Vin or increase Vin over the rated maximum supply voltage of 5.5V, or the part may be damaged. Refer to figure 1 for the proper measurement equipment setup. 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 870A-B HIGH EFFICIENCY MONOLITHIC SYNCHRONOUS BUCK REGULATOR 2. Apply 3.3V at Vin. Measure Vout; it should read 0V. If desired, one can measure the shutdown supply current at this point. The supply current will be approximately 1 uA in shutdown. 3. Turn on the circuit by inserting the shunt in jumper JP1 into the ON position. The output voltage should be regulating. Measure Vout - it should measure 1.8V +/- 2%. 4. Vary the input voltage from 2.25V to 5.5V and adjust the load current from 0 to 0.3A. Vout should read between 1.8V +/- 3%. 5. Measure the output ripple voltage at any output current level; it usually will measure less than 20 mVAC. 6. Observe the voltage waveform at the switch node (one pin of the inductor). Verify the switching frequency is between 1.8 MHz and 2.7 MHz (T = 0.56 us and 0.37 us), and that the switch node waveform is rectangular in shape. When finished, turn off the circuit by inserting the shunt in jumper JP1 into the OFF position. 2 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 870A-B HIGH EFFICIENCY MONOLITHIC SYNCHRONOUS BUCK REGULATOR Figure 1. Proper Measurement Equipment Setup Figure 2. Measuring Input or Output Ripple 3 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 870A-B HIGH EFFICIENCY MONOLITHIC SYNCHRONOUS BUCK REGULATOR Figure 3. Load Step Response Vin = 3.3V, Vout = 1.8V, Iout Step = 0.2A Trace 1: Output Voltage (50 mV/div AC) Trace 2: Output Current (0.1A/div) 4 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 870A-B HIGH EFFICIENCY MONOLITHIC SYNCHRONOUS BUCK REGULATOR 5