QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1343A 2.25MHZ, 1.25A MONOLITHIC SYNCHRONOUS BUCK REGULATOR LTC3564 DESCRIPTION Demonstration circuit DC1343A is a high efficiency age range makes the LTC3564 ideally suited for monolithic synchronous buck regulator using a single Li-Ion battery-powered or 3.3V to 5V input constant frequency, current mode architecture fea- voltage applications. 100% duty cycle provides turing LTC3564. Its high switching frequency of low dropout operation, extending battery life in 2.25MHz allows the use of small surface mount portable systems. Automatic Burst Mode opera- inductors and capacitors. Supply current during tion increases efficiency at light loads, further ex- operation is typically only 20uA, and drops to be- tending battery runtime. Gerber files for this cir- low 1uA in shutdown. The 2.5V to 5.5V input volt- cuit are available. Call the LTC Factory. Table 1. Performance Summary (T = 25C) A PARAMETER CONDITION VALUE Input Voltage 2.5V to 5.5V Output Voltage V I =0A to 1.25A V 1% OUT OUT OUT Maximum Output Current 1.25A DC Supply Current V = 3.3V, V = 1.8V, I = 0A <40mA IN OUT OUT Nominal Switching Frequency V = 3.3V, V = 1.8V, I = 1.25A 2.25MHz IN OUT OUT QUICK START PROCEDURE The DC1343A is easy to set up to evaluate the 2. Before proceeding to operation, insert performance of the LTC3564. Refer to Figure 2 jumper shunt XJP1 into the OFF position and for the proper measurement equipment setup. insert one jumper shunt into XJP2, XJP3 or XJP4 for voltages of 1.2V, 1.5V, or 1.8V respec- NOTE: When measuring the input or output volt- tively. Set the load output current to less than age ripple, care must be taken to avoid a long 1.25A. An optional output voltage can be set by ground lead on the oscilloscope probe. Measure populating resistor RFB6, removing RFB5, and the input or output voltage ripple by touching the moving the shunt to JP5. probe tip directly across the V or V and GND IN OUT terminals. See the measurement example dia- 3. Apply 5V at V . Measure V it should IN OUT gram in Figure 1 for proper scope probe tech- read 0V. If desired, one can measure the shut- nique. down supply current at this point. The supply cur- rent will be about 1 A in shutdown. Please follow the procedure outlined below for proper operation. 4. Turn on V by changing shunt XJP1 from OUT the OFF position to the ON position. The out- 1. Connect the input power supply to the V IN put voltage should measure according to the and GND terminals. Connect the load between voltage set by the shunt in JP2, JP3, or JP4. the V and GND terminals. OUT 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1343A 2.25MHZ, 1.25A MONOLITHIC SYNCHRONOUS BUCK REGULATOR 5. Vary the input voltage between 2.5V and 6. Vary the V load current from 0 to 1.25A, OUT 5.5V and the output voltage should be within +/- and the output voltage should be within a toler- 1% tolerance. ance of +/- 1%. Warning - If the power for the demo board is car- TAJW686M010) on the pads between the in- ried in long leads, the input voltage at the part put power and return terminals on the bottom of could ring, which could affect the operation of the demo board. The (greater) ESR of the tanta- the circuit or even exceed the maximum voltage lum will dampen the (possible) ringing voltage rating of the IC. To eliminate the ringing, insert a due to the use of long input leads. On a normal, small tantalum capacitor (for instance, AVX part typical PCB, with short traces, the capacitor is not needed. Figure 1. Measuring Input or Output Ripple Figure 2. Proper Measurement Equipment Setup Load Step Response 2