QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 856A 500MA, 1.25MHZ SYNCHRONOUS BOOST CONVERTER LTC3427EDC DESCRIPTION Demonstration circuit 856A is a 500mA, 1.25MHz Handsets, GPS Receivers, MP3 players and other Synchronous Boost Converter featuring the Portable Devices. Other integrated features include externally programmable burst mode threshold, in- LTC 3427EDC. The demo circuit demonstrates a ternal compensation, peak current limit, soft-start, DC/DC boost converter, with a 500mA switch current antiringing control and thermal shutdown. For cus- limit, providing 3.3V at 180mA from a 1.8V to 3.6V tomers who do not need the output disconnect fea- input voltage. The input voltage of this supply can go ture of the LTC3427, an efficiency gain of about 3% higher than the output, but thermal limitations reduce can be achieved by adding a small Schottky diode the output current that can be delivered. See between the SW and Vout pins. Vin>Vout Operation section on the datasheet. The circuit demonstrates the advantages of output dis- Design files for this circuit board are available. Call connect and inrush current limiting. Small circuit size the LTC factory. and low component count make the LTC3427 suitable for use in many space-conscious applications such as LTC is a registered trademark of Linear Technology Corporation Hand-Held Instruments, Cordless Phones, Wireless Table 1. Performance Summary (T = 25C) A PARAMETERS CONDITION VALUE Minimum Input Voltage 1.8V Maximum Input Voltage 3.6V Output Voltage V V = 1.8V, I =0mA to 180mA 3.3V 3% OUT IN OUT Output Voltage V V = 3.0V, I =0mA to 180mA 3.3V 3% OUT IN OUT Typical Output Ripple V V = 1.8V, I = 180mA 20mV OUT IN OUT PP Typical efficiency V =3V , I = 180mA 90% IN OUT Typical efficiency V =2V , I = 180mA 85% IN OUT QUICK START PROCEDURE Demonstration circuit 856A is easy to set up to evalu- across the Vin or Vout and Gnd terminals. See ate the performance of the LTC3427EDC. Refer to Figure 2 for proper scope probe technique. Figure 1 for proper measurement equipment setup 1. Place jumpers in the following positions: and follow the procedure below: Run. JP1 NOTE: When measuring the input or output voltage 2. With power off, connect the input power supply to ripple, care must be taken to avoid a long ground lead Vin and Gnd. on the oscilloscope probe. Measure the input or out- put voltage ripple by touching the probe tip directly 3. Turn on the power at the input. 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 856A 500MA, 1.25MHZ SYNCHRONOUS BOOST CONVERTER NOTE: Make sure that the input voltage does not ex- NOTE: Once the proper output voltages are estab- ceed 3.6V. lished, adjust the loads within the operating range and observe the output voltage regulation, ripple 4. Check for the proper output voltages. voltage, efficiency and other parameters. NOTE: If there is no output, temporarily disconnect the load to make sure that the load is not set too high. Figure 1. Proper Measurement Equipment Setup Figure 2. Measuring Input or Output Ripple 2