DEMO CIRCUIT 1434 LT3071 QUICK START GUIDE LT3071 5A, Low Noise, Programmable Output, 85mV Dropout Linear Regulator with Analog Margin DESCRIPTION Demonstration circuit 1434 is an adjustable 5A linear regulator featuring LT3071. LT3071 is a low dropout voltage, UltraFastTM transient response linear regulator. The device supplies up to 5A of output current with a typical dropout voltage of 85mV. A 0.01µF reference bypass capacitor decreases output voltage noise to 25µVRMS. The LT3071’s high bandwidth permits the use of low ESR ceramic capacitors. Output voltage is digitally selectable in 50mV increments over a 0.8V to 1.8V range. An analog margining function allows the user to adjust system output voltage over a continuous ±10% range. To maintain proper performance and regulation, the BIAS supply voltage must be higher than the IN supply voltage. For a given VOUT, the BIAS voltage must satisfy the following conditions: 2.2 ≤ VBIAS ≤ 3.6V and VBIAS ≥ (1.25·VOUT+1V). For VOUT ≤ 0.95V, the minimum bias voltage is limited to 2.2V. Performance Summary (TA = 25oC) PARAMETER Minimum Input Voltage Maximum Input Voltage Minimum Bias Voltage Maximum Bias Voltage Output Voltage VOUT Maximum Output Current The IC incorporates a unique tracking function to control buck regulator powering the LT3071’s input. This tracking function drives the buck regulator to maintain the LT3071’s input voltage to VOUT + 300mV, minimizing power dissipation. It has internal protection includes UVLO, reverse-current protection, precision current limiting with power foldback and thermal shutdown. The LT3071 regulator is available in a thermally enhanced 28-lead, 4mm×5mm QFN package. The LT3071 datasheet gives a complete description of the part, operation and application information. The datasheet must be read in conjunction with this quick start guide for demo circuit 1434. Design files for this circuit board are available. Call the LTC factory. , LTC and LT are registered trademarks of Linear Technology Corporation. UltraFast is a trade mark of Linear Technology Corporation. All other trademarks are the property of their respective owners. CONDITION VOUT=1.2V, IOUT = 5A VOUT=1.2V JP1=LOW, JP2=HIGH, JP3=HIGH VIN -Vout < 0.5V VALUE 1.32V 3V 2.5V 3.6V 1.2V ±1% 5A QUICK START PROCEDURE Demonstration circuit 1434 is easy to set up to evaluate the performance of the LT3071. Refer to Figure 1 for proper measurement equipment setup and follow the procedure below: 1. Place JP5 on the ON position. 1 LT3071 2. Use JP1, JP2, JP3 and MAGRA voltage to set the desired output voltage. 3. With power off, connect the input power supply to Vin and GND. 4. Connect the bias voltage to Vbias and GND. 5. Turn on the power at the input and the bias pin. 7. Once the proper output voltage is established, adjust the load within the operating range and observe the output voltage regulation, efficiency and other parameters. NOTE. Make sure that the power dissipation is lim- ited below the thermal limit. NOTE. Make sure that the input voltage does not exceed 3V and the bias voltage is within its limit. 6. Check for the proper output voltage. NOTE. If there is no output, temporarily disconnect the load to make sure that the load is not set too high. Figure 1. Proper Measurement Equipment Setup 2 * * GND VIN 1.1V - 3V PWRGD VIOC VBIAS E6 E5 E3 E2 E1 JP5 C6 1000pF CIN1 + 220uF 10V (Opt) VIN R1 49.9K 1% OFF 3 POWER 1 ON 2 SEE QUICK START GUIDE FOR VBIAS RANGE 0.01uF C3 CIN2 47uF 10V 1206 U1 LT3071EUFD 8 7 6 5 3 2 1 IN IN IN IN 27 V BIA S 25 VO2 24 VO1 VO0 OUT OUT OUT OUT SE NS E M A RGA IM O N JP2 VO1 23 4 3 2 1 VBIAS 4 9 10 11 12 13 14 20 26 29 GN DG NDGN DG NDGN DG NDGN DG NDGN DG ND REF /BY P P WRGD V IO C EN 28 2.2uF VBIAS VBIAS 4 FLOAT C1 3 JP1 2 LOW 1 HIGH VO2 15 16 17 18 19 22 C4 10uF 10V 0805 JP3 VO0 1K R2 4 FLOAT 21 3 2 1 LOW HIGH VBIAS FLOAT LOW HIGH C7 4.7uF 10V 0805 C8 2.2uF 10V 0805 C5 10uF 10V 0805 E8 E7 E4 E9 GND VOUT 0.8 - 1.8V @ 5A MARGA 0V - 1.2V 2V @ 5A FULL SCALE LT3071 3