DEMO MANUAL DC2392A LTC7860 High Voltage Switching Surge Stopper Description Demonstration circuit 2392A is a high efficiency switching voltage across the current sense resistor and regulates the surge stopper featuring the LTC 7860. The board operates maximum output current to protect against overcurrent from an input range of 7V to 100V, and provides a 7V to faults. An adjustable timer limits the time that the LTC7860 34V output at 0A to 10A. Its output is current limited. A can spend in overvoltage or overcurrent regulation. When soft-start feature controls output voltage slew rate at start- the timer expires, the external MOSFET is turned off until up, reducing current surge and voltage overshoot. The the LTC7860 restarts after a cool down period. By strictly demonstration board includes an optional reverse polarity limiting the time in PROTECTIVE PWM mode when the protection MOSFET and has options for an input filter and power loss is higher, the components and thermal design diode to attenuate spikes. For a lower output voltage limit can be optimized for normal operation and safely oper- of less than 12V, there is an optional feedback circuit. ate through high voltage input surges and/or overcurrent faults. This demo board takes advantage of the LTC7860s The LTC7860 high efficiency surge stopper protects loads V -centric PMOS architecture to float the control ground IN from high voltage transients. High efficiency compared to allowing operation beyond the controllers 60V rating. linear circuits permits higher currents and smaller solution sizes. During an input overvoltage event, such as a load This board is suitable for a wide range of automotive, dump in vehicles, the LTC7860 controls the gate of an military, telecom, industrial, and other applications. The external MOSFET to act as a switching DC/DC regulator LTC7860 is available in a small 12-pin thermally enhanced (PROTECTIVE PWM mode). This operation regulates the MSOP package. For other output requirements, see the output voltage to a safe level, allowing the loads to oper- LTC7860 data sheet or contact the LTC factory. ate through the input overvoltage event. During normal Design files for this circuit board are available at operation (SWITCHON mode), the LTC7860 turns on the DEMO MANUAL DC2392A Quick s tart p D Demonstration circuit 2392 is easy to set up to evaluate 5. Once the proper output voltage is established, connect the performance of the LTC7860. Refer to Figure 1 for a variable load capable of sinking 10A at 34V to the proper measurement equipment setup and follow the output terminals +V and V . Set the current for OUT OUT procedure below: 0A. NOTE: When measuring the output voltage ripple, care must a. A Voltmeter with a capability of measuring at least 36V be taken to avoid a long ground lead on the oscilloscope can be placed across the output terminals in order to probe. Measure the output voltage ripple by touching the get an accurate output voltage measurement. probe tip and ground ring directly across the last output 6. Turn on the power at the input. capacitor as shown in Figure 1. NOTE: If there is no output, temporarily disconnect the 1. Set an input power supply that is capable of 7V to load to make sure that the load is not set too high. 100V to 10V. Then turn off the supply. 7. Once the proper output voltage is again established, 2. With power off, connect the supply to the input termi- adjust the load and/or input within the operating range nals +V and V . IN IN up to 33V and observe the output voltage and other IN a. Input Voltages lower than 7V can keep the converter desired parameters. from turning on due to the undervoltage lockout feature 8. Now apply an input between 35V and 100V and ob- of the LTC7860. serve the output voltage and fault timer operation. b. A voltmeter with a capability of measuring at least 100V 9. If desired, you may apply input transient profiles in can be placed across the input terminals in order to the range of 0V to 100V and observe the output IN IN get an accurate input voltage measurement. to illustrate operation of the circuit to prevent input 3. Turn on the power at the input. surges from reaching the output. NOTE: Make sure that the input voltage never exceeds 10. The output limit voltage can be set in accordance 100V. with the feedback notes on the schematic. The first line shows the complete formula. The second line is 4. Check for the proper output voltage of 10V. Turn off simplified for the use of a 2:1 divider as shown on the the power at the input. schematic. dc2392af 2 ure roce