DC1619A Analog Devices

DEMO MANUAL DC1619A LT3845A: High Voltage Synchronous Buck Controller with Programmable Frequency and Sync DESCRIPTION Demonstration Circuit 1619A is a 100kHz to 500kHz output voltages. In such applications, this optional circuit programmable frequency, high voltage, current mode can increase the overall efficiency by reducing the power DC/DC step-down converter featuring the LT 3845A. The loss in the LT3845A. The demonstration board has the operating frequency can be synchronized up to 600kHz. option of doubling the number of switching MOSFETs to This demo board is designed for 12V up to 10A (120W) facilitate higher output current. This board is suitable for output from a 16V to 60V input. A soft-start feature controls a wide range of industrial control systems and telecom the output voltage slew rate at start-up, reducing current power supplies. surges and voltage overshoots. The modes of operation The LT3845A data sheet gives a complete description of (Burst Mode , discontinuous current mode and continuous the part, operation and application information. The data current mode) are jumper selectable. Both Burst Mode sheet must be read in conjunction with this quick start operation and discontinuous current mode increase the guide for demo circuit 1619A. efficiency at light loads. Continuous current mode will Note: It is best to ground the SYNC pin if the SYNC func- maintain a constant switching frequency regardless of tion is not being used. the load current. Design files for this circuit board are available at An optional boost bias circuit is provided on the bottom DEMO MANUAL DC1619A QUICK START PROCEDURE Demonstration circuit 1619A is easy to set up to evaluate 4. Turn on the power at the input and adjust the input the performance of the LT3845A. Refer to Figure 1 for voltage until the LT3845A turns on. proper measurement equipment setup and follow the Note: Make sure that the input voltage does not ex- procedure below: ceed60V. Note: When measuring the input or output voltage ripple, 5. Check for the proper output voltage. care must be taken to avoid a long ground lead on the Note: If output does not come up, make sure the load oscilloscope probe. Measure the input or output volt- is not set too high. Reduce the load and repeat steps age ripple directly across the VIN or VOUT capacitors by 4 and5. soldering leads on the appropriate capacitor. See Figure 2 for proper scope probe technique. An oscilloscope probe 6. Once the proper output voltage is established, adjust the can be directly connected to VIN or VOUT using a banana input voltage and load within the operating range and jack to BNC adaptors. observe the output voltage regulation, ripple voltage, efficiency and other parameters. 1. Place JP1 in the RUN position. 7. An external clock can be added to the SYNC pin when 2. Place JP2 in the desired operating mode: burst, pulse- the SYNC function is used. See the Oscillator SYNC skipping or continuous. section in the data sheet for details. 3. With power off, connect the input power supply to VIN and GND. 0V TO 60V LOAD 7.5A 0A TO 10A + + + A DC1619 F01 Figure 1. Proper Measurement Equipment Setup dc1619af 2 A + + + V V