QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 471 2A, 200KHZ HIGH VOLTAGE BUCK CONVERTER LT3430 DESCRIPTION Demonstration circuit 471 is a 60V, 200kHz, 2A chronization of switching frequencies up to load current, monolithic step-down DC/DC 700kHz is possible. switching converter using the LT3430. With its Demonstration Circuit 471 is a step-down wide input voltage range, 3A internal power converter using the LT3430. The circuit is de- switch, and thermally enhanced package, signed for 7.5V60V input to 5.0V output at 2A the LT3430 is a very versatile and powerful IC load current for automotive, industrial, port- for DC/DC converters that require compact able computers, battery chargers, and dis- space and a wide variety of input voltage tributed power systems. This board was de- ranges. The constant 200kHz switching fre- signed for wide input voltage range applica- quency allows all of the components to be tions where simplicity, small circuit size, and small, surface mount devices. The current- low component count are important as well mode control topology creates fast transient as up to 2A of load current. The low-ESR tan- response and good loop stability with a mini- talum output capacitor reduces output volt- mum number of external compensation age ripple. Replacing this capacitor with a components and the use of ceramic input ceramic capacitor not only demonstrates and output capacitors if desired. The low resis- small size and low cost, but the advantage of tance internal power switch (0.1 ) maintains current-mode control in step-down applica- high efficiencies >80% and up to 90%. The tions with a simple compensation network SHDN pin and 30A shutdown current extend and a feedforward capacitor for more rug- battery life. The wide input range allows step- ged stability and excellent transient response. down configurations with input voltages be- Design files for this circuit board are available. tween 5.5V and 60V. Both steady state and Call the LTC factory. transient operation up to 60V is possible. Syn- Table 1. Typical Performance Summary PARAMETER CONDITION VALUE Steady State Input Voltage Range V = 5V, I 2A 7.5 60V OUT OUT Maximum Transient Input Voltage All Vout (customized) 60V V I 2A 5V 3% OUT OUT Maximum Output Current 2A Typical Switching Frequency 200kHz Typical Efficiency V = 12V, V = 5V, I = 2A 86% IN OUT OUT Output Voltage Ripple V = 12V, V = 5V, I = 2A 30mV IN OUT OUT PP QUICK START PROCEDURE Demonstration circuit 471 is easy to set up to NOTE: Make sure that the input voltage does evaluate the performance of the LT3430. Re- not exceed 60V. fer to Figure 1 for proper measurement equip- 1. Connect the 7.5V60V input power supply ment setup and follow the procedure below: to the Vin and GND terminals on the board. 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 471 2A, 200KHZ HIGH VOLTAGE BUCK CONVERTER 2. Connect an ammeter in series with the in- 6. Connect a voltmeter across the Vout and put supply to measure input current. GND terminal to measure output voltage. 3. Connect either power resistors or an elec- 7. After all connections are made, turn on in- tronic load to the Vout and GND terminals put power and verify that the output volt- on the board. age is 5.0V. 4. Connect an ammeter in series with output 8. The synchronization and shutdown func- load to measure output current. tions are optional and their pins can be left floating (disconnected) if their functions are 5. Connect a voltmeter across the Vin and not being used. GND terminals to measure input voltage. + LOAD + + + OPTIONAL Figure 1. Proper Measurement Equipment Setup 100 90 80 70 60 8VIN 50 12VIN 40 24VIN 30 48VIN 20 55VIN 10 0 0 400 800 1.2k 1.6k 2.0k LOAD CURRENT (mA) Figure 2. Efficiency vs Load Current 2 EFFICIENCY (%) + + +