DEMO MANUAL DC1734A LT8582 Dual 3A Boost/Inverting/SEPIC DC/DC Converter DESCRIPTION Demonstration circuit 1734A features the dual channel To change the topology of channel 1 from boost to invert- LT 8582 in boost and inverting regulator configurations. ing: Replace D1 with a capacitor similar to C12, replace The circuit is designed to convert a 5V to 10V input source C2 with a diode similar to D3, placing the diode so that to 12V at 900mA and 12V at 590mA as shown in Table 1. its cathode is connected to ground, and replace R16 with an inductor similar to L3. Table 1. Maximum Guaranteed Output Currents To change the topology of channel 2 from inverting to boost: V (V) MAX I (mA) MAX I (mA) IN LOAD1 LOAD2 Replace C12 with a diode similar to D1, placing the diode so 4.5 775 540 that its anode is connected to L2, replace D3 with a capacitor 5.0 900 590 similar to C2, and replace L3 with a jumper resistor similar 5.5 1000 625 to R16. However, this configuration will not be output short To limit the temperature rise of the chip to 40C, on the protected since it lacks the external disconnect MOSFET. demo board with no air flow, the maximum combined Each channel of the LT8582 includes a 42V master and slave output power is 15W. Additional input bulk capacitance power switch combination with 3A total current and can easily may be needed, subject to source impedance. be configured as a boost, SEPIC, inverting or flyback converter. DC1734A is designed to survive output short circuit events. The LT8582 has a 2.5V to 22V operating input range, UVLO, On the positive channel an external disconnect MOSFET soft-start, programmable switching frequency and many other protects the boost converter. The negative channel is features. The LT8582 data sheet gives a complete description based on dual inductor inverting topology and does not of the part, its operation and application information. The need the external MOSFET as it is inherently output short data sheet must be read in conjunction with this quick start protected. The circuit board includes an option to install guide for working on or modifying the demo circuit 1734A. the external disconnect MOSFET at the input side of the Design files for this circuit board are available at positive channel. To use it, remove Q1 and R1 from the DEMO MANUAL DC1734A QUICK START PROCEDURE Demonstration circuit DC1734A is easy to set up to evalu- 1. Place the on board jumpers in the following positions: ate the performance of the LT8582. Refer to Figure 1 for To activate boost converter: JP1 ON proper measurement equipment set-up and follow the To activate inverting converter: JP2 ON procedure below. 2. With power off, connect the input power supply to V To measure voltage ripple, care must be taken to avoid a IN and GND. Apply 7.5V to the input (source must have long ground lead on the oscilloscope probe. Remove the greater than 10A capability). oscilloscope probe end cap and ground lead and set the bandwidth limit on the oscilloscope. Measure the input 3. Check for the proper output voltages. voltage ripple by touching the probe tip and ground directly NOTE. If there is no output, temporarily disconnect the across V and GND terminals. See Figure 2 for proper IN load to make sure that the load is not set too high. input voltage ripple measurement technique. Measure the positive output voltage ripple by touching the probe tip 4. Once the proper output voltage is established, adjust directly across output capacitor C16 terminals, connect- the load and the input voltage within the operating ing the probe ground terminal to the boards GND plane. range and observe the output voltage regulation, ripple Measure the negative output voltage ripple by touching the voltage, efficiency and other parameters. The efficiency probe tip directly across output capacitor C9, connecting graphs of the two channels are provided in Figure 4 the probe ground terminal to the boards GND plane. See and Figure 5. Figure 3 for proper output voltage ripple measurement technique. Figure 1. Proper Measurement Equipment Setup dc1734af 2