MIL-STD-1275D is a standard created by the U.S. Department of Defense that specifies the steady-state characteristics and transient voltage of a 28 VDC power supply in a military ground vehicle. When faced with the strong transients, spikes, and waveforms specified in MIL-STD-1275D, the DC2150A solution limits the output voltage to a safe 44V. In most applications, meeting the standard is as simple as placing the DC2150A circuit in front of a 44V-tolerant device. The DC2150A uses the LTC4366 and LT4363 transient surge suppressor ICs, which drive series N-channel MOSFETs, thus reducing the size and cost of the solution compared to traditional shunt circuits that use bulky capacitors, fuses, inductors, and transient voltage suppressors.
The DC2150A solution is designed to withstand input transients up to ±250V and to deliver a minimum current of 4A to the load under all conditions except ±7V ripple, when the available current drops to 2.8A. The N-channel MOSFETs are protected against output overloads by current limiting. A sustained overvoltage or overcurrent disables the circuit after a time delay; the circuit automatically reconnects after a recovery cycle. Thermal protection circuitry disconnects the LT4363-controlled MOSFET when the temperature exceeds 105°C.
The DC2150A solution has four mounting options (DC2150A-A to DC2150A-D), depending on the maximum load current and the ability to handle 100V transient spikes for 500ms. Bill of materials costs are reduced by choosing board options that eliminate unnecessary protection features. Only the fully featured option, DC2150A-C, is available, priced at $150.00 per unit. The solution is described in detail in the Linear Technology Journal of Analog Innovation, Volume 24, Number 1, "High Voltage Surge Stoppers Ease MIL-STD-1275D Compliance by Replacing Bulky Passive Components."

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