DEMO MANUAL DC2195A LT8609 42V, 2A Micropower Synchronous Step-Down Regulator Description Demonstration circuit 2195A is a 42V, 2A micropower move JP1 to SYNC and apply the external clock to the synchronous step-down regulator featuring the LT8609. SYNC turret. Figure 1 shows the efficiency of the circuit. The demo board is designed for 5V output from a 5.5V to The demo board has an EMI filter installed. Under spread 42V input. The wide input range allows a variety of input spectrum operation, the radiated EMI performances of the sources, such as automotive batteries and industrial sup- board (with EMI filter) are shown in Figures 2 and 3. The red plies. The LT8609 is a compact, high efficiency, high speed lines in Figures 2 and 3 are CISPR25 Class 5 peak limit. To synchronous monolithic step-down switching regulator use the EMI filter, the input should be tied to VEMI, not V . IN that consumes only 2.5A of quiescent current when This board is suitable for a wide range of automotive, output is regulated at 5V. Top and bottom power switches, telecom, industrial, and other applications. compensation components and other necessary circuits are inside of the LT8609 to minimize external components The LT8609 data sheet gives a complete description of and simplify design. the part, operation and application information. The data sheet must be read in conjunction with this demo manual The SYNC pin on the demo board is grounded by default for DC2195A. for low ripple burst mode operation. Move JP1 to PULSE SKIPPING position can change the operation mode to pulse- Design files for this circuit board are available at skipping operation. Once JP1 is on SPREAD SPECTRUM DEMO MANUAL DC2195A Quick s p D DC2195A is easy to set up to evaluate the performance a. If efficiency measurements are desired, an ammeter of the LT8609. Refer to Figure 4 for proper measurement can be put in series with the output load in order to equipment setup and follow the procedure below: measure the DC2195As output current. NOTE: When measuring the input or output voltage ripple, b. A voltmeter can be placed across the output terminals care must be taken to avoid a long ground lead on the in order to get an accurate output voltage measurement. oscilloscope probe. See Figure 5 for the proper scope 6. Turn on the power at the input. technique. NOTE: If there is no output, temporarily disconnect the 1. Set an input power supply that is capable of 42V/2A. load to make sure that the load is not set too high. Then turn off the supply. 7. Once the proper output voltage is again established, 2. With power off, connect the supply to the input terminals adjust the load and/or input within the operating range V and GND. EMI and observe the output voltage regulation, ripple volt- 3. Turn on the power at the input. age, efficiency and other desired parameters. NOTE: Make sure that the input voltage never exceeds 42V. 8. An external clock can be added to the SYNC ter- minal when SYNC function is used (JP1 on the 4. Check for the proper output voltage of 5V. Turn off the SYNC position). Please ensure that the chosen R T power at the input. sets the LT8609 switching frequency to equal or 5. Once the proper output voltage is established, connect below the lowest SYNC frequency. See the data a variable load capable of sinking 2A at 5V to the output sheet section, Synchronization. terminals V and GND. Set the current for 0A. OUT 100 95 90 85 80 75 70 65 60 55 12V INPUT 24V INPUT 50 0 0.5 1 1.5 2 I (A) OUT DC2195 F01 Figure 1. Efficiency vs Load Current at 2MHz Switching Frequency dc2195afb 2 EFFICIENCY (%) ure roce tart