QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 870A-B HIGH EFFICIENCY MONOLITHIC SYNCHRONOUS BUCK REGULATOR LTC3410B DESCRIPTION Demonstration circuit 870A-B is a high efficiency, DC870 is a very efficient circuit: up to 96%. These high frequency buck converter, incorporating the features, plus the LTC3410B coming in a tiny, low- LTC3410B monolithic synchronous regulator. The profile 6-Pin SC70 package, make the DC870 demo DC870 has an input voltage range of 2.25V to 5.5V, board an ideal circuit for use in battery-powered, and is capable of delivering up to 300 mA of output hand-held applications. current. It has an output voltage range from 0.8V to Design files for this circuit board are available. Call 5V, and an operating frequency range of 2.25 MHz the LTC factory. (allowing the exclusive use of low profile surface TM - Burst Mode is a trademark of Linear Technology Corporation mount components). In low load current operation, the LTC3410B operates in pulse-skip mode. The Table 1. Performance Summary (T = 25C) A PARAMETER CONDITION VALUE Minimum Input Voltage 2.25V Maximum Input Voltage 5.5V 1.8V 4% Output Voltage V V = 2.25V to 5.5V, I = 0A to 0.3A OUT IN OUT Typical Output Ripple V V = 5V, I = 0.3A (20 MHz BW) 20mV OUT IN OUT PP Line 1% Output Regulation Load 1% Nominal Switching Frequency 2.25 MHz QUICK START PROCEDURE The DC870A-B is easy to set up to evaluate the per- put voltage ripple by touching the probe tip directly formance of the LTC3410B. For proper measurement across the Vin or Vout and GND terminals. See Fig- equipment configuration, set up the circuit according ure 2 for proper scope probe technique. to the diagram in Figure 1. Before proceeding to test, insert jumper JP1 shunt into the off position, con- 1. Connect the input power supply and the load to the necting the RUN pin to ground (GND), which shuts board. Do not hot-plug Vin or increase Vin over down the circuit. the rated maximum supply voltage of 5.5V, or the NOTE: When measuring the input or output voltage part may be damaged. Refer to figure 1 for the ripple, care must be taken to avoid a long ground lead proper measurement equipment setup. on the oscilloscope probe. Measure the input or out- 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 5. Measure the output ripple voltage at any output 0V. If desired, one can measure the shutdown current level it usually will measure less than 20 supply current at this point. The supply current mVAC. will be approximately 1 uA in shutdown. 6. Observe the voltage waveform at the switch node 3. Turn on the circuit by inserting the shunt in jumper (one pin of the inductor). Verify the switching fre- JP1 into the ON position. The output voltage quency is between 1.8 MHz and 2.7 MHz (T = 0.56 should be regulating. Measure Vout - it should us and 0.37 us), and that the switch node wave- measure 1.8V +/- 2%. form is rectangular in shape. 4. Vary the input voltage from 2.25V to 5.5V and ad- When finished, turn off the circuit by inserting the just the load current from 0 to 0.3A. Vout should shunt in jumper JP1 into the OFF position. read between 1.8V +/- 3%. 2