DEMONSTRATION CIRCUIT 1424A-A/B QUICK START GUIDE LT3581 BOOST/INVERTING DC/DC CONVERTERS DESCRIPTION Demonstration circuits 1424A-A and 1424A-B as Boost, SEPIC, CUK and Flyback. It has a feature the LT3581 in Boost/Inverting Regulator 2.5V to 22V operating input range, UVLO, soft- configurations. The Boost is designed to con- start, programmable switching frequency and vert a 5V to 10V input source to 12V at 900mA, many other popular features. The LT3581 is and the Inverter a 5V to 12V to -12V at 750mA. suitable for many applications, such as Local DC1424A-A is designed to survive output short Bias Supplies, VFD, TFT-LCD Supplies and circuit events with the external MOSFET in- Automotive Engine Control Power. The LT3581 stalled at the output as default. The demo board datasheet gives a complete description of the part, includes an option to install the MOSFET at the its operation and application information. The input side. Install Q1 and R1 on the back of the datasheet must be read in conjunction with this board and refer to Figure 4 for other instruc- quick start guide for working on or modifying the tions. DC1424A-B can easily be converted into demo circuit 1424A. a SEPIC Converter by swapping L2 and D2 from their respective locations as shown in Fig- Design files for this circuit board are ure 5. The LT3581 includes a 42V Master and available. Call the LTC factory. Slave switch combination with 3.3A total current LT is a trademark of Linear Technology Corporation and can be used in many configurations such PERFORMANCE SUMMARY DC1424A-A Specifications are at TA = 25C SYMBOL PARAMETER FOR BOOST CONVERTER CONDITIONS MIN TYP MAX UNITS V Input Supply Range 5 10 V IN V Output Voltage Accuracy V = 5V to 10V, I = 900mA 11.60 12 12.30 V OUT IN LOAD Efficiency V = 5V, I = 900mA 88 % IN LOAD Ripple V = 5V, I = 900mA 100 mV IN LOAD Fs Switching Frequency 1.2 MHz PERFORMANCE SUMMARY 1424A-B Specifications are at TA = 25C SYMBOL PARAMETER FOR CUK CONVERTER CONDITIONS MIN TYP MAX UNITS V Input Supply Range 5 12 V IN V Output Voltage Accuracy V = 5V to -12V, I = 750mA -11.60 -11.9 -12.30 V OUT IN LOAD Efficiency V = 5V, I = 750mA 81 % IN LOAD Ripple V = 5V, I = 750mA 20 mV IN LOAD Fs Switching Frequency 1.2 MHz 1 DEMONSTRATION CIRCUIT 1424A-A/B QUICK START GUIDE QUICK START PROCEDURE Demonstration circuit 1424A-A and 1424A-B is easy to set up to evaluate the performance of the LT3581. Refer to Figures 1 and 2 for proper measurement equipment setup and follow the procedure below: When 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 jumper in the following position: JP1 On 2. With power off, connect the input power supply to Vin and GND. Apply 5V to input. 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. Once the proper output voltage is established, adjust the load within the operating range and observe the output voltage regulation, ripple voltage, efficiency and other parameters. 2