DEMO MANUAL DC1853A LT3959 Wide Input Voltage Range Boost/SEPIC/Inverting Converter DESCRIPTION The LT 3959 is a current mode DC/DC converter with an The demo circuit has small circuit footprint, and can be integrated 6A, 40V switch. It can operate over an input modified to generate different output voltages. The perfor- range of 1.6V to 40V, suitable for applications from single- mance can be optimized for different input voltage ranges cell lithium-ion battery portable electronics up to high as well. It is a high performance and cost-effective solution voltage automotive and industrial power supplies. It also for battery-operated systems, telecom, and automotive exhibits low shutdown quiescent current of <1A, making applications. it an ideal fit for battery-operated systems. Thanks to a The LT3959 data sheet gives a complete description of novel FBX pin architecture, the LT3959 can be connected the part, operation and application information. The data directly to a divider from either positive or negative output sheet must be read in conjunction with this quick start to ground. It also packs many popular features such as guide. Proper board layout is essential for both proper soft-start, input undervoltage lockout, adjustable frequency operation and maximum thermal performance. See the and synchronization. Applications Information section of the data sheet for Demonstration circuit 1853A features LT3959 in a 300kHz more information. boost converter, designed for 12V output from 2V to 10V Design files for this circuit board are available at input (V ). The performance is summarized in the table IN DEMO MANUAL DC1853A QUICK START PROCEDURE Demo circuit 1853A is easy to set up to evaluate the per- NOTE. The demo circuit configures the shutdown volt- formance of LT3959. Refer to Figure 1 for proper measure- age at 2V, which means that the input voltage can be ment equipment setup and follow the procedure below. dropped to as low as 2V, once it starts up. The startup voltage is set at 2.5V, and can be adjusted by changing 1. With power off, connect the input power supply, load R1 and R2 values. and meters as shown in Figure 1. Preset the load to 0A, and V supply to be 0V. Place jumpers in the following NOTE. The output current capability depends on the IN positions. input voltage. The output current is up to 0.5A for V IN higher than 2V, 1A for V higher than 5V, and 2A for IN EN (JP1) SYNC (JP2) V higher than 9V. IN ON OFF 3. Once the proper output voltage is established, adjust 2. Turn on V and increase to 2.5V. Check for proper the input voltage and load within the operating range IN output voltages. The output should be regulated at and observe the output voltage regulation, ripple volt- 12V (3%). The switching frequency should be about age, efficiency and other parameters. Typical efficiency 300kHz. curve is shown in Figure 3. NOTE. If there is no output, or the output is out of spec, NOTE. When measuring the input or output voltage temporarily disconnect the load to make sure that the ripples, care must be taken to avoid a long ground load is not set too high. lead on the oscilloscope probe. Measure the input or output voltage ripple by touching the probe tip directly NOTE. Make sure that the input voltage does not exceed across the V and GND, or V and GND terminals. IN OUT specification. If higher operating voltage is required, See Figure 2 for proper scope probe technique. power components with higher voltage ratings should be used. The maximum voltage is 40V for the integrated switch of LT3959. Figure 1. Proper Measurement Equipment Setup dc1853af 2