QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 568 DUAL SYNCHRONOUS, 600MA, 1.5MHZ STEP-DOWN DC/DC REGULATOR LTC3407 DESCRIPTION Demonstration circuit 568 is a Dual Synchronous, comes in a small 10-Pin MS10E package, which has 600mA, 1.5MHz Step-Down DC/DC Regulator featur- an exposed pad on the bottom-side of the IC for bet- ing the LTC 3407. The DC568 has an input voltage ter thermal performance. These features, plus the range of 2.5V to 5.5V, and either output is capable of nominal operating frequency of 1.5MHz (allowing the delivering up to 600mA of output current. In Burst exclusive use of low profile surface mount compo- Mode operation, the LTC3407 requires only 40 uA nents), make the DC568 demo board an ideal circuit of quiescent current, and the DC568 provides higher for use in battery-powered, hand-held applications. efficiency at light load currents. In Pulse Skip mode, Design files for this circuit board are available. the DC568 provides lower output ripple voltage at Call the LTC factory. light load currents. In either mode, the DC568 can LTC and Burst Mode is registered trademark of Linear Technology Corporation. provide up to 96% efficiency on either channel and consumes less than 1uA in shutdown. The LTC3407 Table 1. Performance Summary (T = 25C) A PARAMETER CONDITION VALUE Minimum Input Voltage 2.5V Maximum Input Voltage 5.5V 1.2V 2% Output Voltage V V = 2.5V to 5.5V, I = 0A to 600 mA 1.5V 2% OUT1 IN OUT1 1.8V 2% Typical Output Ripple V V = 5V, I = 600 mA (20 MHz BW) 20mV OUT1 IN OUT1 PP Line 1% Output Regulation Load 1% Output Voltage V V = 2.5V to 5.5V, I = 0A to 600 mA 2.5V 2% OUT2 IN OUT2 Typical Output Ripple V V = 5V, I = 600 mA (20 MHz BW) 20mV OUT2 IN OUT2 PP Line 1% Output Regulation Load 1% Nominal Switching Frequency 1.5 MHz QUICK START PROCEDURE Demonstration circuit 568 is easy to set up to NOTE: When measuring the input or output voltage evaluate the performance of the LTC3407. Refer to ripple, care must be taken to avoid a long ground lead Figure 1 for proper measurement equipment setup on the oscilloscope probe. Measure the input or and follow the procedure below: output voltage ripple by touching the probe tip 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 568 DUAL SYNCHRONOUS, 600MA, 1.5MHZ STEP-DOWN DC/DC REGULATOR directly across the V or V and GND terminals. 4. Turn on V 1 and V 2 by changing jumpers IN OUT OUT OUT See Figure 2 for proper scope probe technique. JP1 and JP2 from the OFF position(s) to the ON position(s). Vary the input voltage from 2.5V to 1. Connect the input power supply to the V and IN 5.5V and adjust each load current from 0 to GND terminals on the left-side of the board. Do 600mA. Both output voltages should be not hot-plug V or increase V over the rated IN IN regulating. maximum supply voltage of 5.5V, or the part may be damaged. Connect the loads between the V 5. Set the load current of both outputs between 200 OUT and GND terminals on the right-side of the board. mA and 600 mA, and measure both output ripple Refer to figure 1 for the proper measurement voltages they should measure less than 20 mVAC equipment setup. each. Also, observe the voltage waveform at the switch node (pin 3) of each regulator. The 2. Before proceeding to operation, insert jumpers JP1 switching frequencies should be between 1.2 MHz and JP2 into the OFF positions, jumper JP3 into and 1.8 MHz (T = 0.833 us and 0.555 us), and each the V 1 voltage position of choice (1.2V, 1.5V, OUT switch node waveform should be rectangular in and 1.8V), and jumper JP4 into the desired mode shape. of operation: Pulse Skip or Burst Mode. 6. To change the mode of operation, change jumpers 3. Apply 3.3V at V . Measure both V s they IN OUT JP1 and JP2 from the ON position(s) to the OFF should read 0V. If desired, one can measure the position(s). Then change jumper JP4 to the shutdown supply current at this point. The supply alternative position. Re-insert jumpers JP1 and current will be approximately 33 uA in shutdown, JP2 into the ON position(s). Observe the voltage with roughly 32 uA due to the optional 100k pull- waveform at both switch nodes. up resistor of the Power-On Reset (POR) feature. This resistor can be removed, and the actual When finished, insert jumpers JP1 and JP2 to the shutdown supply current can be measured, if the OFF position(s) and disconnect the power. POR feature is not required. 2