DEMO MANUAL DC2067A LT8710 Synchronous Inverting DC/DC Converter DESCRIPTION Demonstration circuit 2067A is a synchronous inverting 2. The optional RC snubber (R4, C1) across the flying converter (CUK topology) featuring the LT 8710 switching capacitor could help to damp the feedback control loop controller. It regulates a 5V, 6A output from a 4.5V to 28V for some applications using two separate inductors. input source, and operates at 300kHz switching frequency. 3. The optional input capacitors (CIN5, CIN6) or output The LT8710 features simple negative or positive output capacitors (CO5, CO6) could be installed to reduce voltage programming. The DC2067 programs a 5V output voltage ripple for some low voltage and/or high current with a single resistor. applications. At light load, the LT8710 can operate at forced continuous 4. The optional RC (R24, C19) snubber could be installed to conduction mode (CCM) or discontinuous conduction damp the switch node spike and reduce the EMI noise. mode (DCM), set by its MODE pin. The DC2067A selects 5. The optional current sensing resistor filters (located near DCM, which maintains high efficiency at light load. CSP and CSN pins, ISP and ISN pins) might be required The DC2067A can be modified from a CUK converter to in certain applications with excessive switching noise. other topology. Synchronous SEPIC and synchronous The LT8710 data sheet gives a complete description of BOOST schematics are provided in the data sheet. Please the part, operation and application information. The data consult the factory or LT8710 data sheet for details re- sheet must be read in conjunction with this quick start garding how to customize the DC2067A or how to design guide for demo circuit 2067A. different topologies for custom specifications. Design files for this circuit board are available at There are some optional components on the DC2067A to DEMO MANUAL DC2067A QUICK START PROCEDURE Demonstration circuit 2067A is easy to set up to evalu- Note: When measuring the input or output voltage ripples, ate the performance of the LT8710. Refer to Figure 1 for care must be taken to avoid a long ground lead on the proper measurement equipment setup and follow the oscilloscope probe. Measure the input or output voltage procedure below: ripple by touching the probe tip directly across the VIN and PGND, or VOUT and PGND terminals. See Figure 2 1. With the power off, connect the input power supply to for proper scope probe technique. the board through VIN and PGND terminals. Connect the load to the terminals VOUT and PGND on the board. 5. The DC2067A is equipped with an output capacitor Make sure that the input power supply has sufficient CO1 (270F) that approximates typical system rail current rating at minimum input voltage for the required capacitance. If the system board already has capaci- output load. tance of similar value, CO1 can be removed. The input capacitor CIN1 is used to help with filtering when the 2. Turn on the power at the input. board is connected to lab power supply with long leads. Note: Make sure that the input voltage does not exceed 28V. The capacitor CIN1 can be removed if the input power source is close and has low source impedance. 3. Check for the proper output voltages. The output should be regulated at 5.0V (3%). If there is no output, temporarily disconnect the load to make sure that the load is not set too high. 4. Once the proper output voltage is established, adjust the input voltage and load current within the operating range and observe the output voltage regulation, ripple voltage, efficiency and other parameters. dc2067af 2