MIL-STD-704F データシートの表示（PDF） - Sensitron

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MIL-STD-704F

DC Solid State Power Controller Module

Sensitron 

SENSITRON

SEMICONDUCTOR

TECHNICAL DATA

DATASHEET 4310, Rev B

Figure 4 - Electrical Block Diagram

SPDXXD28 SERIES

Description

Figure 4 shows the block diagram of the SPDXXD28 SSPC Series. It uses a SN74LVC3G14 device for digital

I/O. This TTL compatible device has a Schmitt-Trigger input to minimize the effects of noise on the input. Its

outputs can each drive more than 10 standard TTL loads. It’s also compatible with CMOS inputs and outputs.

The SN74LVC3G14 is isolated from the remainder of the module circuitry by three optocouplers.

The block labeled “Control & Protection Circuitry” gets power from the DC-DC converter and is referenced to the

output of the SSPC. This block contains an amplifier to gain up the voltage developed across the sense

resistor. It also contains a microcontroller with on-board timers, A/D converter, clock generator and independent

watchdog timer. The microcontroller implements a precision I2t protection curve as well as an Instant Trip

function to protect the wiring and to protect itself. It performs all of the functions of multiple analog comparators

and discrete logic in one high-reliability component.

The code programmed in the microcontroller acquires the output of the internal A/D converter, squares the

result and applies it to a simulated RC circuit. It checks the output of the simulated circuit to determine whether

or not to trip (turn off the power Mosfets). Because the microcontroller simulates an analog RC circuit, the

SSPC has ‘thermal memory’. That is, it trips faster if there had been current flowing prior to the overload than if

there hadn’t been current flowing. This behavior imitates thermal circuit breakers and better protects the

application’s wiring since the wiring cannot take as much an overload if current had been flowing prior to the

overload.

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