QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 613 3A, 500KHZ, STEP-DOWN CONVERTER WITH 100UA QUIESCENT CURRENT LT3435IFE DESCRIPTION Demonstration circuit 613 is a 3A, 500kHz, step- Innovative design techniques along with a new high down converter with 100uA quiescent current featur- voltage process achieve high efficiency over a wide ing the LT3435IFE. It produces 5V at 2A from an in- input range. Efficiency is maintained over a wide put range of 6.75V to 28V continuous, and can sur- output current range by employing Burst Mode op- vive input transients up to 60V. The demonstration eration at low currents, utilizing the output to bias the circuit includes a shutdown control, synchronization internal circuitry, and by using a supply boost capaci- from 500kHz to 700kHz and a programmable power tor to fully saturate the power switch. good indicator. For further information about the LT3435, please refer The LT3435 is a 500kHz monolithic buck switching to the LT3435 data sheet. regulator that accepts input voltages up to 60V. A Design files for this circuit board are available. Call high efficiency 3A, 0.1W switch is included on the die the LTC factory. along with all the necessary oscillator, control and , LTC , LT and Burst Mode are registered trademarks of Linear Technology logic circuitry. Current mode topology is used for Corporation. fast transient response and good loop stability. Table 1. Performance Summary (T = 25C) A PARAMETER CONDITION VALUE Minimum Turn On Input Voltage V = 5VDC, I = 2A 6.75VDC OUT LOAD Minimum Turn Off Input Voltage V = 5VDC, I = 2A 6.5V, typical OUT LOAD Continuous 28VDC Maximum Input Voltage 100mS transient 60VDC Output Voltage V V = 6.75 to 28VDC, I = 0 to 2A 5V + 4% OUT IN LOAD Maximum Output Current V = 6.75 to 28VDC, V = 5VDC 2A IN OUT Nominal Switching Frequency 500kHz Synchronization Frequency Range V = 6.75 to 28VDC, V = 5VDC 500 700 KHz IN OUT QUICK START PROCEDURE Demonstration circuit 613 is easy to set up to evalu- across the VIN or VOUT and GND terminals. See ate the performance of the LT3435IFE. Refer to Figure 2 for proper scope probe technique. Figure 1 for proper measurement equipment setup 1. While disconnected from the demonstration circuit, and follow the procedure below: set the output of the input power source to its NOTE: When measuring the input or output voltage minimum positive value. ripple, care must be taken to avoid a long ground lead 2. With power off, connect the input power supply to on the oscilloscope probe. Measure the input or out- VIN and GND. put voltage ripple by touching the probe tip directly 3. Connect the load. 1 GND VIN QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 613 3A, 500KHZ, STEP-DOWN CONVERTER WITH 100UA QUIESCENT CURRENT 4. Turn on the power at the input, ensuring that the 7. Verify the shutdown by pulling the SHDN (TP4) voltage applied to the demonstration circuit is less terminal to a logic low level. than 28VDC. 8. Verify the power good function by monitoring the 5. Check for the proper output voltages. The output timing and voltage levels of the output voltage and VOUT should be 5VDC. PGOOD terminal (TP7). NOTE: If there is no output, temporarily disconnect 9. Verify the synchronization function by applying a the load to make sure that the load is not set too square wave signal of the appropriate amplitude high. and frequency to the SYNC terminal (TP5). 6. Once the proper output voltages are established, adjust the loads within the operating range and ob- serve the output voltage regulation, ripple voltage, efficiency and other parameters. Figure 1. Proper Measurement Equipment Setup Figure 2. Measuring Input or Output Ripple 2