DEMO MANUAL DC2435A-A/ DC2435A-B/DC2435A-C LTC7813EUH 4V to 56V V , Step-Up/Step-Down IN Power Supply Description Demonstration circuit DC2435A is a step-up/down sup- The LTC7813 buck input is supplied from the Boost output ply featuring the LTC 7813EUH. The LTC7813 is a high for the DC2435A-A and DC2435A-B only. With this boost- performance dual output (buck and boost) synchronous then-buck topology, the buck outputs maintain regulation DC/DC switching regulator controller. The board has three over the entire input range of 4V to 56V, making it suitable different configurations: for automotive or other battery fed applications where low quiescent current is important. DC2435A-A: Regulated output voltage of 24 Volt The DC2435A-B is designed such that V is partially OUT DC2435A-B: Narrowed output voltage between 20V and regulated between 20V and 28V for higher efficiency 28V (Figure 5a), reduced power loss, and switching noise. DC2435A-C: Dual output voltages of 24V (Boost V BUS When V is between 20V and 28V, it operates in pass- IN channel) and 5V (Buck V channel) OUT1 thru mode with the boost synchronous FET fully on and the buck in drop-out with >99% duty cycle. When V is IN The circuit enables a drop-in layout where the total circuit below 20V, the boost is activated and when V is above IN area is only 1 by 1 . The LTC7813EUH is in a 32-lead 28V, the buck is activated as shown in Figure 5b. exposed pad QFN package. The LTC7813 data sheet gives a complete description of The main features of the board include rail tracking (buck the part, operation and application information and must channel only), an internal 5V linear regulator for bias, be read in conjunction with this quick start guide. separate RUN pins for each output and a Mode selector that allows the converter to run in CCM, pulse-skipping Design files for this circuit board are available at or Burst Mode operation. Synchronization to an external DEMO MANUAL DC2435A-A/ DC2435A-B/DC2435A-C Demo Boar D o Figure 1. DC2435A/LTC7813 Demo Board Options Quick s tart p D DC2435A is easy to set up to evaluate the performance of 3. Turn on the power at the input. the LTC7813EUH. Refer to Figure 2 for proper measure- NOTE: Make sure that the input voltage is higher than ment equipment setup and follow the procedure below: 8V and does not exceed 56V. NOTE: When measuring the input or output voltage ripple, 4. Check for the proper output voltages for different care must be taken to avoid a long ground lead on the boards. oscilloscope probe. Measure the input or output voltage -A: V = 23.5V to 24.5V, ripple by touching the probe tip directly across the V OUT1 IN or V and GND terminals or directly across relevant OUT -B: 19V < V < 28.6V, OUT1 capacitor. See Figure 3 for proper scope probe technique. -C: V = 4.9V to 5.1V OUT1 1. Place jumpers in the following positions: V = 23.5V to 24.5V (V < 24V) BUS IN JP1 ON NOTE: If there is no output, temporarily disconnect the load to make sure that the load is not set too high. JP2 ON 5. Once the proper output voltages are established, adjust JP3 FCM the loads within the operating range and observe the 2. With power off, connect the input power supply to V IN output voltage regulation, ripple voltage, efficiency and GND. and other parameters. dc2435af 2 ure roce ptions