MIL-STD-217F データシートの表示（PDF） - Sensitron
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MIL-STD-217F Datasheet PDF : 11 Pages
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SENSITRON
SEMICONDUCTOR
SPDXXD28 SERIES
TECHNICAL DATA
DATASHEET 4310, Rev B
The watchdog timer operates from its own internal clock so a failure of the main clock will not stop the watchdog
timer. The code programmed in the microcontroller will periodically reset the watchdog timer preventing it from
timing out. If the code malfunctions for any reason, the watchdog timer is not reset and it times out. When the
watchdog timer times out, it resets the microcontroller. Since the code is designed to detect levels and not
edges, the output of the module, and therefore the output of the SPDXXD28, immediately reflects the command
on its input.
The Power Mosfets used in the SPDXXD28 Series have been selected for very low Rds(on) and results in low
voltage drop and low power dissipation. In most applications, the SPDXXD28 will be operated at 50 – 60% of
rated current to provide a safety margin. As can be seen in Table 1, when the SPD25D28 is operated at 15
Amps, 60% of rated current, it only dissipates 1.0 Watt at room temperature. No heatsinking is required for this
condition. However, if the SPD25D28 is to be operated at maximum rating and/or at elevated temperatures, the
dissipation can exceed 4 Watts and heatsinking is required. Some heatsinking can be accomplished by adding
copper area to the LINE and LOAD pins, a heatsink can be epoxied to the surface of the module or a flat copper
or aluminum heatsink can be sandwiched between the SPD25D28 and the printed circuit board using a thermal
pad to maximize heat transfer. Each application should be evaluated at maximum expected constant current.
For overloads, no heatsinking is required provided the SPDXXD28 Series is allowed some time to cool down.
The SPDXXD28 has sufficient thermal mass that the temperature will rise only a few degrees under the worst-
case overload. Repetitive overloads should be avoided. When the SPDXXD28 reports a trip condition, the
controller driving the SPDXXD28 should allow no more than four repetitions and then allow thirty seconds to
cool down before trying to turn on again.
The SPDXXD28 will trip on overloads in the ALWAYS TRIP region shown in Figure 1 and will never trip when in
the NEVER TRIP region. The SPDXXD28 can be reset by bringing the CONTROL pin to a logic low. When the
CONTROL pin is brought back to logic high, the SPDXXD28 will turn back on. If the overload is still present, the
SPDXXD28 will trip again. Cycling the 5 Volt BIAS power will also reset the SPDXXD28. If the CONTROL pin
is at logic high when the BIAS power is cycled, the SPDXXD28 will turn back on when the BIAS power is re-
applied.
Status Outputs
The LOAD and GATE status outputs of the SPDXXD28 show whether or not the load is drawing current and
whether or not the SPDXXD28 Power Mosfet switch is on. A logic high on the LOAD status output shows that
the load draws < 5% of rated load and a logic low shows that the load draws > 15% of rated current. A load that
draws between 5% and 15% of rated current could result in either a high or low logic level on the LOAD status
output. A logic high on the GATE output indicates that the Power Mosfet switch is on while a logic low indicates
that the switch is off.
As can be seen in Table 4, of the 8 possible states for the combination of CONTROL, LOAD and GATE, only 3
states represent valid SSPC operation. The other 5 states indicate either a failed SSPC or, more likely, a short
to ground or a short to the BIAS supply of one of the logic outputs. By comparing the CONTROL input with the
LOAD and GATE outputs, the user can determine whether or not the load is supposed to be ON (GATE),
whether or not it’s drawing current (GATE) and whether or not the LOAD and GATE outputs are valid responses
to the CONTROL input.
Table 4 – CONTROL, LOAD & GATE Truth Table
State CONTROL LOAD
GATE
Comments
1
L
L
L
SSPC failure or shorted LOAD output to ground
2
L
L
H
SSPC failure
3
L
H
L
Normal OFF condition
4
L
H
H
SSPC failure or shorted GATE output to BIAS supply
5
H
L
L
SSPC failure or shorted GATE output to ground
6
H
L
H
Normal ON condition with load current > 15% rated current
7
H
H
L
Tripped
8
H
H
H
Normal ON condition with load current < 5% rated current
• 221 West Industry Court Deer Park, NY 11729-4681 Phone (631) 586 7600 Fax (631) 242 9798 •
• World Wide Web - http://www.sensitron.com • E-Mail Address - sales@sensitron.com •
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