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dc2150af

DEMO MANUAL DC2150A

QUICK START PROCEDURE

Connect a 28V supply to the input and connect a load at

the output. A good output load choice is a 10Ω power

resistor rated at more than 200W. If the banana jacks are

used, no connections are necessary at the turrets. The

green LED turns on to indicate that the output is powered.

If the load at the output sinks less than 28mA, place

jumper JP1 in the 1kΩ position to preload the output (be

aware that preload resistors R34 and R35 may become

hot as they dissipate nearly 2W when the input is at 44V).

With less than 28mA of load current, MIL-STD-1275D’s

repeated 100V/50ms input surge test causes capacitors

C1-C12 to remain charged at 67V for an extended period

of time while the output voltage is regulated to 44V. This

is not harmful, but it may cause the LT4363 to timeout

and shutoff Q4.

Now, lower the input voltage to 8V. The output remains

powered. In fact, the output remains powered to even

DC2150A is available from Linear Technology as

DC2150A-C. This C version provides 4A to the load dur-

ing all conditions except the ripple condition, where 2.8A

is available to the load for up to one minute. Exceeding

2.8A during the ripple condition may cause the circuit to

timeout in less than one minute. DC2150A-C provides un-

interrupted power to the load during both the 100V/500ms

worst-case surge envelope of MIL-STD-1275D and the

repeated 100V/50ms recommended test. (Figure 1 shows

DC2150A-C riding through the 100V/500ms surge. Figure

2 shows it riding through the repeated 100V/50ms surges.

Figure5showsDC2150A-Cprovidinguninterruptedpower

during a ±7V input ripple event.)

Schematics and a bill of materials are provided for three

additional assembly options. Versions DC2150A-A and

DC2150A-B provide a minimum of 2A of current to the load

lower voltages, but component tolerances, especially the

MOSFET threshold voltages, prevent guaranteed opera-

tion below 8V.

Next, raise the input voltage above 50V. The output shuts

offasthecircuitdetectsahighinputvoltage.Oncetheinput

is brought back to 28V, the output power is automatically

reapplied after a cooldown timer cycle. Be patient, it can

take 30 seconds for power to be reapplied.

MIL-STD-1275D Requirements

Refer to Linear Technology Journal article, High Voltage

Surge Stoppers Ease MIL-STD-1275D Compliance by

Replacing Bulky Passive Components, and the MIL-STD-

1275D, Characteristics of 28 Volt DC Electrical Systems in

Military Vehicles, United States Department of Defense In-

terfaceStandardforathoroughdescriptionofrequirements.

andridethroughthe100V/50msrepeatedsurgesspecified

intheMIL-STD-1275Drecommendedtests.Theseversions

are not guaranteed to ride through the worst-case 500ms

envelope in the MIL-STD-1275D specifications. No dam-

age will occur, but these versions may shut off when faced

with the full 100V/500ms worst-case envelope. Versions

DC2150A-C and DC2150A-D provide at least 4A of current

totheloadandridethroughthe100V/50msrepeatedsurges

and the full worst-case 100V/500ms surge. (Refer to the

MIL-STD-1275D standard and Linear Technology Journal

article,HighVoltageSurgeStoppersEaseMIL-STD-1275D

CompliancebyReplacingBulkyPassiveComponents,fora

morethoroughdescriptionoftheserequirements.)Versions

DC2150A-A and DC2150A-C provide 1A and 2.8A during

the ripple condition, respectively. Versions DC2150A-B

and DC2150A-D shutoff immediately when ripple occurs

on the input, but they have a reduced bill of materials cost.

ASSEMBLY OPTIONS

Table 1. DC2150A Assembly Options

STUFFING OPTION

MAX LOAD

MAX LOAD DURING RIPPLE

100V/50ms SURGE

(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