DEMO MANUAL DC1602A LT3741 High Power Constant Current, Constant Voltage Synchronous Buck Controller Description Demonstration circuit 1602A is a high power constant 100W, a couple of percent of efficiency improvement is current, constant voltage synchronous buck controller a huge advantage in minimizing temperature rise. If an featuring the LT 3741. The demo board is optimized for efficiency measurement is needed in an application, the 20A output from a 12V input. Being an LED driver, the output voltage must be measured at the output capacitors output current is being regulated until the output voltage instead of at the LED load. This prevents cable loss from reaches a programmed voltage limit. The voltage limit on being counted as a loss of the board. Output current can this demo board is set to around 6V by R11 and R14. The be adjusted by varying the CTRL1 voltage. 6V is chosen because of the 10V voltage rating of the output R16 can be used to slow down the gate drive. Slower gate capacitors. Higher output voltage can be easily achieved drive helps to reduce ringing on the SW node without with higher voltage rated output capacitors. The ideal load noticeable effect on the efficiency. A 10 is usually more to be used with this demo board is a single LED, such as than enough to completely damp any ringing. PT120 from Luminus Devices. Smaller LEDs may not be R10, R13 and C14 help filtering out voltage spikes seen able to handle the high current, even for a short period of + on the SENSE or SENSE pin. It is critical to have those time. At 20A, the demo circuit can operate continuously. components on a board. However, it is necessary to mount the LED load on a proper heat sink and possibly with a fan to avoid exceeding its The LT3741 data sheet gives a complete description of maximum temperate rating. the part, operation and application information. The data sheet must be read in conjunction with this quick start The input voltage range of the LT3741 itself is 6V to 36V. guide for demo circuit 1602A. However, the demo board utilizes 30V MOSFETs to demon- strate best efficiency, so the maximum recommended input Design files for this circuit board are available at voltage is 24V for the demo board. The typical efficiency DEMO MANUAL DC1602A Quick s tart p D Demonstration circuit 1602A is easy to set up to evalu- 2. With power off, connect a LED between V and GND. OUT ate the performance of the LT3741. Refer to Figure 1 for 3. Turn on the power at the input. Be careful not to look proper measurement equipment setup and follow the at a powered LED directly. procedure below: 4. Carefully evaluate other design parameters as needed. 1. With power off, connect the input power supply to 5. Adjust CTRL1 to change output current. PV and GND. The input power supply should have a IN current limit of 10A or more. 6. To modify the demo board for other applications, please contact Linear Applications Group for help. + + LOAD + DC1602 F01 Figure 1. Proper Measurement Equipment Setup dc1602af 2 ure roce