DC770C Analog Devices

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 770C LT3782A DESCRIPTION Demonstration circuit DC770C is a DC/DC boost con- The DC770C has a small circuit footprint. It is a high verter featuring the LT3782A constant frequency current performance and cost effective solution for Telecom, mode boost controller. The DC770C operates over 10V Automotive and Power-Over-Ethernet applications. to 28V input and provides 4A of output current at 50V output. The 250kHz constant frequency operation results Design files for this circuit board are available. Call in a small and efficient circuit. The converter provides the LTC factory. high output voltage accuracy (typically 3%) over wide load range with no minimum load requirement. LT is a trademark of Linear Technology Corporation The demonstration circuit can be easily modified to gen- erate different output voltages. Please consult LTC fac- tory for details. QUICK START PROCEDURE Demonstration circuit DC770C is easy to set up to evalu- 4. Check for the proper output voltage of 50V. ate the performance of the LT3782A. For proper meas- If there is no output, temporarily disconnect the load urement equipment setup refer to Figure 1 and follow to make sure that the load is not set too high. the procedure below: 5. Once the proper output voltage is established, adjust NOTE: When measuring the input or output voltage rip- the load within the 4A range and observe the output ple, care must be taken to minimize the length of the voltage regulation, ripple voltage, efficiency and other oscilloscope probe ground lead. Measure the input or parameters output voltage ripple by connecting the probe tip directly across the VIN or VOUT and GND terminals as shown in Figure 2. 1. With power off, connect the input power supply to VIN and GND. 2. Check the Vcc Bias voltage-setting jumper JP3. Move it to the VIN position if required. 3. Turn the input power source on and slowly increase the input voltage. Be careful not to exceed 28V. NOTE: Make sure that the input voltage VIN does not exceed 28V. If higher operating voltage is required, power components with higher voltage ratings should be used. Also, Jumper JP3 will have to be moved to the 15V position. 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 770C PROGRAMMING OF SYNCHRONOUS RECTIFIER DELAY In that case, the DELAY pin voltage can be derived from the R pin. The R pin generates a 2.3V reference volt- SET SET age that can be divided down to the desired value by If synchronous rectifier MOSFETs are used, the delay of resistors R and R . outputs SGATE1 and SGATE2 can be programmed by the 9 13 voltage on the DELAY pin. Keep in mind that R +R are used to set the switching 9 13 frequency. In order to keep frequency constant, R +R 9 13 should stay constant as well. Please refer to the data sheet for more information. Figure 1. Proper Measurement Equipment Setup 2