DEMO MANUAL DC2150A LTC4366-2/LT4363-2 28V MIL-STD-1275D Surge Stopper DESCRIPTION Demonstration circuit 2150A uses the LTC 4366-2 and MIL-STD-1275Ds one minute ripple ride-through require- LT4363-2 surge stoppers to satisfy MIL-STD-1275D. This ment. DC2150As MOSFETs are protected against output specification, created by the United States Department of overloads by current limiting. Sustained overvoltage or Defense, sets down requirements of electrical systems overcurrent conditions cause the circuit to turn off after a powered from a military vehicles 28V power supply. timer delay. It automatically retries after a cooldown cycle. DC2150As output voltage is limited to 44V when faced DANGER HIGH VOLTAGE TESTING SHOULD BE with MIL-STD-1275Ds onerous surge, spike, and ripple PERFORMED BY QUALIFIED PERSONNEL ONLY. conditions. In most circumstances, satisfying MIL-STD- AS A SAFETY PRECAUTION AT LEAST TWO PEOPLE 1275D is as simple as placing this circuit in front of a 44V SHOULD BE PRESENT DURING HIGH VOLTAGE tolerant device. The default version, DC2150A-C, provides TESTING. a minimum of 4A to the output in all conditions except the 7V ripple condition (14Vpeak-to-peak). During the ripple Design files for this circuit board are available at condition, DC2150A-C provides a minimum of 2.8A to the DEMO MANUAL DC2150A QUICK START PROCEDURE Connect a 28V supply to the input and connect a load at lower voltages, but component tolerances, especially the the output. A good output load choice is a 10 power MOSFET threshold voltages, prevent guaranteed opera- resistor rated at more than 200W. If the banana jacks are tion below 8V. used, no connections are necessary at the turrets. The Next, raise the input voltage above 50V. The output shuts green LED turns on to indicate that the output is powered. off as the circuit detects a high input voltage. Once the input If the load at the output sinks less than 28mA, place is brought back to 28V, the output power is automatically jumper JP1 in the 1k position to preload the output (be reapplied after a cooldown timer cycle. Be patient, it can aware that preload resistors R34 and R35 may become take 30 seconds for power to be reapplied. hot as they dissipate nearly 2W when the input is at 44V). MIL-STD-1275D Requirements With less than 28mA of load current, MIL-STD-1275Ds repeated 100V/50ms input surge test causes capacitors Refer to Linear Technology Journal article, High Voltage C1-C12 to remain charged at 67V for an extended period Surge Stoppers Ease MIL-STD-1275D Compliance by of time while the output voltage is regulated to 44V. This Replacing Bulky Passive Components, and the MIL-STD- is not harmful, but it may cause the LT4363 to timeout 1275D, Characteristics of 28 Volt DC Electrical Systems in and shutoff Q4. Military Vehicles, United States Department of Defense In- terface Standard for a thorough description of requirements. Now, lower the input voltage to 8V. The output remains powered. In fact, the output remains powered to even ASSEMBLY OPTIONS DC2150A is available from Linear Technology as and ride through the 100V/50ms repeated surges specified DC2150A-C. This C version provides 4A to the load dur- in the MIL-STD-1275D recommended tests. These versions ing all conditions except the ripple condition, where 2.8A are not guaranteed to ride through the worst-case 500ms is available to the load for up to one minute. Exceeding envelope in the MIL-STD-1275D specifications. No dam- 2.8A during the ripple condition may cause the circuit to age will occur, but these versions may shut off when faced timeout in less than one minute. DC2150A-C provides un- with the full 100V/500ms worst-case envelope. Versions interrupted power to the load during both the 100V/500ms DC2150A-C and DC2150A-D provide at least 4A of current worst-case surge envelope of MIL-STD-1275D and the to the load and ride through the 100V/50ms repeated surges repeated 100V/50ms recommended test. (Figure 1 shows and the full worst-case 100V/500ms surge. (Refer to the DC2150A-C riding through the 100V/500ms surge. Figure MIL-STD-1275D standard and Linear Technology Journal 2 shows it riding through the repeated 100V/50ms surges. article, High Voltage Surge Stoppers Ease MIL-STD-1275D Figure 5 shows DC2150A-C providing uninterrupted power Compliance by Replacing Bulky Passive Components, for a during a 7V input ripple event.) more thorough description of these requirements.) Versions DC2150A-A and DC2150A-C provide 1A and 2.8A during Schematics and a bill of materials are provided for three the ripple condition, respectively. Versions DC2150A-B additional assembly options. Versions DC2150A-A and and DC2150A-D shutoff immediately when ripple occurs DC2150A-B provide a minimum of 2A of current to the load on the input, but they have a reduced bill of materials cost. Table 1. DC2150A Assembly Options 100V/50ms SURGE STUFFING OPTION MAX LOAD MAX LOAD DURING RIPPLE (FIVE REPEATS) 100V/500ms SURGE DC2150A-A 2A 1A Yes No DC2150A-B 2A N/A Yes No DC2150A-C 4A 2.8A Yes Yes DC2150A-D 4A N/A Yes Yes dc2150af 2