DEMO MANUAL DC1832A LT3995 60V, 3A, 2MHz Step-Down Switching Regulator with 2.7A Quiescent Current Description Demonstration circuit 1832A is a monolithic step-down voltage lockout. A low dropout voltage of 500mV is main- DC/DC switching regulator featuring the LT3995. The tained when the input voltage drops below the programmed LT3995 is a compact, high efficiency monolithic step-down output voltage. During a short-circuit fault, the LT3995 switching regulator that consumes only 2.7A of quiescent has current limit foldback to limit the power dissipation. current. The demo circuit is designed for 3.3V, 3A output The demo board has an EMI filter installed. The EMI from a 4.3V to 60V input. The switching frequency can be performance of the demo board at 12V input voltage is programmed either via oscillator resistor or external clock shown on Figure 2. The limit in Figure 2 is EN55022 Class up to 2MHz. To synchronize to an external clock, move B. The figure shows the circuit passes the test with a wide JP2 to SYNC and apply the external clock to the SYNC margin. To use the EMI filter, the input should be tied to turret. The RT resistor (R5) should be chosen to set the VEMI not V . IN LT3995 internal switching frequency at least 20% below The LT3995 data sheet gives a complete description of the lowest synchronization input frequency. the part, operation and application information. The data Low ripple Burst Mode operation increases the effi- sheet must be read in conjunction with this demo manual ciency at the light load while keeping the output ripple for demo circuit 1832A. The LT3995 is assembled in a 16- below 15mV. The SYNC pin on the demo board is grounded lead plastic MSOP package with an exposed pad for low by default by setting JP2 at RT FREQ for low ripple thermal resistance. Proper board layout is essential for Burst Mode operation. Figure1 shows the demo board both proper operation and maximum thermal performance. efficiency at 12V input voltage. See the data sheet sections for details. The LT3995 is in shutdown when the EN pin is low and Design files for this circuit board are available at active when the pin is high. The threshold of the EN pin DEMO MANUAL DC1832A p s Specifications are at T = 25C A PARAMETER CONDITIONS VALUE Guaranteed Minimum Input Voltage 4.3V Maximum Input Voltage 60V Output Voltage V V = 4.3V ~ 60V 3.275V 3% OUT IN Switching Frequency R = 182k 300kHz 20% T Guaranteed Maximum Output Current I V = 4.3V ~ 60V 3A OUT IN Typical Efficiency V = 12V, I = 3A 82.2% IN OUT Typical Output Voltage Ripple V = 12V, I = 3A 11mV IN OUT Quick s Dp Demonstration circuit 1832A is easy to set up to evalu- 4. With power off, connect load from V to GND. OUT ate the performance of the LT3995. Refer to Figure 3 5. Turn on the power at the input. for proper measurement equipment setup and use the 6. Check for the proper output voltage (3.3V). following procedure. NOTE. If there is no output, temporarily disconnect the NOTE. When measuring the input or output voltage ripple, load to make sure that the load is not set too high or care must be taken to avoid a long ground lead on the is shorted. oscilloscope probe. Measure the input or output voltage ripple by touching the probe tip directly across the V IN 7. Once the proper output voltage is established, adjust or V and GND terminals. See Figure 4 for the proper OUT the load within the operating ranges and observe the scope technique. output voltage regulation, ripple voltage, efficiency and other parameters. 1. Place JP1 on the ON position. 8. An external clock can be added to the SYNC terminal 2. Place JP2 on the RT FREQ position. when SYNC function is used (JP2 on the SYNC posi- 3. With power off, connect the input power supply to V IN tion). Please make sure that the SYNC frequency is at and GND. Make sure that the input voltage does not least 20% higher than the set switching frequency. exceed 60V. See the data sheet Synchronization section. dc1832af 2 ure roce tart ummary erformance