QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 870A-A HIGH EFFICIENCY MONOLITHIC SYNCHRONOUS BUCK REGULATOR LTC3410 DESCRIPTION Demonstration circuit 870A-A is a high efficiency, at no load, and less than 1uA in shutdown The high frequency buck converter, incorporating the DC870 is a very efficient circuit: up to 96%. These LTC3410 monolithic synchronous regulator. The features, plus the LTC3410 coming in a tiny, low- DC870 has an input voltage range of 2.25V to 5.5V, profile 6-pin SC70 package, make the DC870 demo and is capable of delivering up to 300mA of output board an ideal circuit for use in battery-powered, current. It has an output voltage range from 0.8V to hand-held applications. 5V, and an operating frequency of 2.25MHz (allowing Design files for this circuit board are available. Call the exclusive use of low profile surface mount com- the LTC factory. ponents). In Burst Mode operation, which is the LTC and Burst Mode are trademarks of Linear Technology Corporation mode of low load current operation offered by the LTC3410, the DC supply current is typically only 26uA 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-A is easy to set up to evaluate the per- on the oscilloscope probe. Measure the input or out- formance of the LTC3410. For proper measurement put voltage ripple by touching the probe tip directly equipment configuration, set up the circuit according across the Vin or Vout and GND terminals. See to the diagram in Figure 1. Before proceeding to test, Figure 2 for proper scope probe technique. insert shunt on jumper JP1 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 proper ripple, care must be taken to avoid a long ground lead measurement equipment setup. 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 870A-A 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 should measure less than 20mVAC. supply current at this point. The supply current 6. Observe the voltage waveform at the switch node will be approximately 1uA in shutdown. (one pin of the inductor). Verify the switching fre- 3. Turn on the circuit by inserting the shunt in jumper quency is between 1.8MHz and 2.7MHz (T = JP1 into the ON position. The output voltage 0.56us and 0.37us), and that the switch node should be regulating. Measure Vout it should waveform is rectangular in shape. measure 1.8V +/- 2%. TM The Burst-Mode capability of the LTC3410 can be 4. Vary the input voltage from 2.25V to 5.5V and ad- observed now by reducing load current. just the load current from 0 to 0.3A. Vout should When finished, turn off the circuit by inserting the read 1.8V +/- 3%. shunt in jumper JP1 into the OFF position. Figure 1. Proper Measurement Equipment Setup 2