QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 701 DUAL SYNCHRONOUS, 600MA, 1.5MHZ STEP-DOWN DC/DC REGULATOR LTC3407 DESCRIPTION Demonstration circuit 701 is a Dual Synchronous, comes in a small 10-Pin DFN package, which has an 600mA, 1.5MHz Step-Down DC/DC Regulator featur- exposed pad on the bottom-side of the IC for better ing the LTC 3407. The DC701 has an input voltage thermal performance. These features, plus the nomi- range of 2.5V to 5.5V, and either output is capable of nal operating frequency of 1.5MHz (allowing the ex- delivering up to 600mA of output current. In Burst clusive use of low profile surface mount compo- Mode operation, the LTC3407 requires only 40 uA nents), make the DC701 demo board an ideal circuit of quiescent current, and the DC701 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. Call the DC701 provides lower output ripple voltage at the LTC factory. light load currents. In either mode, the DC701 can LTC is a 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 701 is easy to set up to evalu- for proper measurement equipment setup and follow ate the performance of the LTC3407. Refer to Figure 1 the procedure below. 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 701 DUAL SYNCHRONOUS, 600MA, 1.5MHZ STEP-DOWN DC/DC REGULATOR Note: When measuring the input or output voltage with roughly 32 uA due to the optional 100 kW ripple, care must be taken to avoid a long ground lead pull-up resistor of the Power-On Reset (POR) fea- on the oscilloscope probe. Measure the input or out- ture. This resistor can be removed, and the actual put voltage ripple by touching the probe tip directly shutdown supply current (of approx. 1 uA) can be across the Vin or Vout and GND terminals. See Figure measured, if the POR feature is not required. 2 for proper scope probe technique. 4. Turn on Vout1 and Vout2 by changing jumpers JP1 Note: Capacitor C5 is an optional part. It was in- and JP2 from the OFF position(s) to the ON posi- serted on the DC701 to dampen the (possible) ringing tion(s). Vary the input voltage from 2.5V to 5.5V voltage due to the use of long input leads. On a nor- and adjust each load current from 0 to 600mA. mal, typical PCB, with short traces, the capacitor is Both output voltages should be regulating. not needed. 5. Set the load current of both outputs between 200 1. Connect the input power supply to the Vin and mA and 600 mA, and measure both output ripple GND terminals on the left-side of the board. Do voltages they should measure less than 20 mVAC not hot-plug Vin or increase Vin over the rated each. Also, observe the voltage waveform at the maximum supply voltage of 5.5V, or the part may switch node (pin 3) of each regulator. The switch- be damaged. Connect the loads between the Vout ing frequencies should be between 1.2 MHz and and GND terminals on the right-side of the board. 1.8 MHz (T = 0.833 us and 0.555 us), and each Refer to Figure 1 for the proper measurement switch node waveform should be rectangular in equipment setup. shape. 2. Before proceeding to operation, insert jumpers JP1 6. To change the mode of operation, change jumpers and JP2 into the OFF positions, jumper JP3 into JP1 and JP2 from the ON position(s) to the OFF the Vout1 voltage position of choice (1.2V, 1.5V, position(s). Then change jumper JP4 to the alter- and 1.8V), and jumper JP4 into the desired mode native position. Re-insert jumpers JP1 and JP2 of operation: Pulse Skip or Burst Mode. into the ON position(s). Observe the voltage wave- form at both switch nodes. 3. Apply 3.3V at Vin. Measure both Vouts they should read 0V. If desired, one can measure the When finished, insert jumpers JP1 and JP2 to the shutdown supply current at this point. The supply OFF position(s) and disconnect the power. current will be approximately 33 uA in shutdown, If more efficiency is desired from the Demo Circuit, replace the stock inductor, a Taiyo Yuden part LQLBC2518M2R2M, with a Murata inductor, LQH32CN2R2M11. Due to its large size, the Murata inductor has lower DCR than the Taiyo Yuden inductor, thus has less power dissipation. 2