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