QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 560 WCDMA CELLULAR PHONE BUCK REGULATOR LTC3403EDD DESCRIPTION Demonstration circuit 560 is a constant-frequency step- cally only 20A at no load, and less than 1A in shut- down converter, using the LTC3403 monolithic synchro- down. nous buck regulator. It is specifically designed for The LTC3403 comes in a small 8-Pin DFN package and WCDMA power amplifier applications. The output volt- has an operating frequency of 1.5MHz (allowing the ex- age can be dynamically controlled from 0.3V to 3.5V. A clusive use of low profile surface mount components). 0.2 internal bypass P-channel MOSFET connects the These and other features make demonstration circuit V to V reducing the power loss through the buck OUT IN 560 ideal for single-cell Li-ion-powered hand-held appli- regulator. DC560 is capable of delivering up to 600mA of cations. output current for an input voltage range of 2.7V to 5V. The efficiency of the DC560 is very high: up to 96%. In Design files for this circuit board are available. Call TM Burst Mode operation, the DC supply current is typi- the LTC factory. QUICK START PROCEDURE Demonstration circuit 560 is easy to set up to evaluate 5. Turn on the V power supply. REF the performance of the LTC3403EDD. Refer to Figure 1 NOTE: Make sure that the input voltage V does not REF for proper measurement equipment setup and follow the exceed V . IN procedure below: 6. For VREF < 1.2V, check for the output voltages NOTE: When measuring the input or output voltage rip- V = 3 V OUT REF ple, care must be taken to avoid a long ground lead on 7. For V > 1.2V, VOUT is directly connected to VIN. the oscilloscope probe. Measure the input or output REF V = V . voltage ripple by touching the probe tip directly across OUT IN the Vin or Vout and GND terminals. See Figure 2 for If there is no output, temporarily disconnect the load proper scope probe technique. to make sure that the load is not set too high. 1. Place jumper JP2 in the FC position, JP1 in the ON 8. Once the proper output voltages are established, ad- position. just the loads within 600mA range and observe the output voltage regulation, ripple voltage, efficiency 2. With power off, connect the input power supply V to IN and other parameters. VIN and GND. TM 9. To test Burst Mode operation, set JP2 in the Burst 3. Connect input power supply V to REF and GND. REF position and JP1 in the ON position, and repeat steps 4. Turn on the power at VIN. 2 to 7. NOTE: Make sure that the input voltage at VIN does not exceed 5V. 1 GND VIN QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 560 WCDMA CELLULAR PHONE BUCK REGULATOR BENCH LOAD SUPPLY + + + + + Figure 2. Scope Probe Placement for Figure 1. Proper Measurement Equipment Setup Measuring Input or Output Ripple Figure 3. Ch1: VOUT (100mV / Div) Transient Response for 0 to 600mA Figure 4. 1.5V Output Ripple load Step. Ch2: IOUT (500mA / Div) (V = 3.3V, I = 600mA) IN OUT (V = 3.3V, V = 1.2V) IN OUT 2 + +