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PDF ADDC02828SAKV Data sheet ( Hoja de datos )
| Número de pieza | ADDC02828SAKV | |
| Descripción | 28 V/100 W DC/DC Converter with Integral EMI Filter | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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FEATURES
28 V dc Input, 28 V dc @ 3.6 A, 100 W Output
Integral EMI Filter Designed to Meet MIL-STD-461D
Low Weight: 80 Grams
NAVMAT Derated
Many Protection and System Features
APPLICATIONS
Commercial and Military Airborne Electronics
Missile Electronics
Space-Based Antennae and Vehicles
Mobile/Portable Ground Equipment
Distributed Power Architecture for Active Array Radar
28 V/100 W DC/DC Converter
with Integral EMI Filter
ADDC02828SA
FUNCTIONAL BLOCK DIAGRAM
– SENSE
+ SENSE
ADJUST
STATUS
VAUX
INHIBIT
SYNC
ISHARE
TEMP
–VIN
+VIN
OUTPUT SIDE
CONTROL
CIRCUIT
INPUT SIDE
CONTROL
CIRCUIT
EMI FILTER
FIXED
FREQUENCY
DUAL
INTERLEAVED
POWER TRAIN
OUTPUT
FILTER
RETURN
RETURN
SENSEREF
SENSEREF
+VOUT
+VOUT
ADDC02828SA
GENERAL DESCRIPTION
The ADDC02828SA hybrid dc/dc converter with integral EMI
filter offers the highest power density of any dc/dc converter
available today with its features and in its power range. The
converter with integral EMI filter is a fixed frequency, 1 MHz,
square wave switching dc/dc power supply. It is not a variable
frequency resonant converter. In addition to many protection
features, this converter has system level features that allow it to
be used as a component in larger systems as well as a stand-
alone power supply. The unit is designed for high reliability and
high performance applications where saving space and/or weight
is critical.
The ADDC02828SA is available in three screening grades; all
grades use a hermetically sealed, molybdenum based hybrid
package. Contact factory for MIL-STD-883 device availability.
PRODUCT HIGHLIGHTS
1. 60 W/cubic inch power density with an integral EMI filter
designed to meet all applicable requirements in MIL-STD-
461D when installed in a typical system setup.
2. Light weight: 80 grams
3. Operational and survivable over a wide range of input condi-
tions: 16 V–50 V dc; survives low line, high line and positive
and negative transients. See Input Voltage Range section.
4. High reliability; NAVMAT derated
5. Protection Features Include:
Output Overvoltage Protection
Output Short Circuit Current Protection
Thermal Monitor/Shutdown
Input Overvoltage Shutdown
Input Transient Protection
6. System Level Features Include:
Current Sharing for Parallel Operation
Inhibit Control
Output Status Signal
Synchronization for Multiple Units
Input Referenced Auxiliary Voltage Supply
REV. 0
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700 World Wide Web Site: http://www.analog.com
Fax: 617/326-8703
© Analog Devices, Inc., 1997
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–100
10
100 1k 10k
FREQUENCY – Hz
50k
Figure 7. Audio Susceptibility (Magnitude of VOUT/VIN)
10.0
1.0
28Vdc
18Vdc
–0.1
–0.01
10
100 1k 10k
FREQUENCY – Hz
100k
Figure 8. Incremental Input Impedance (Magnitude)
ADDC02828SA
1.0
0.1
.01
.001
10
100 1k 10k
FREQUENCY – Hz
100k
Figure 9. Incremental Output Impedance (Magnitude)
1mV
100µV
2.00 MHz/Div
Figure 10. Output Voltage Ripple Spectrum
REV. 0
–5–
5 Page 
ADDC02828SA
For the power delivery to be efficient, it is required that RS << RN.
For the system to be stable, however, the following relationship
must hold:
CP|RN|>
(LS + LP
RS
)
or
RS
>
(LS + LP )
CP|RN|
Notice from this result that if (LS + LP) is too large, or if RS is
too small, the system might be unstable. This condition would
first be observed at low input line and full load since the abso-
lute value of RN is smallest at this operating condition.
If an instability results, and it cannot be corrected by changing
LS or RS (such as during the MIL-STD-461D tests) due to the
LISN requirement, one possible solution is to place a capacitor
across the input of the POL converter. Another possibility is to
place a small resistor in series with this extra capacitor.
The analysis so far has assumed the source of power was a volt-
age source (e.g., a battery) with some source impedance. In
some cases, this source may be the output of a front-end (FE)
converter. Although each FE converter is different, a model for
a typical one would have an LC output filter driven by a voltage
source whose value was determined by the feedback loop. The
LC filter usually has a high Q, so the compensation of the
feedback loop is chosen to help dampen any oscillations that
result from load transients. In effect, the feedback loop adds
“positive resistance” to the LC network.
When the POL converter is connected to the output of this FE
converter, the POL’s “negative resistance” counteracts the
effects of the FE’s “positive resistance” offered by the feedback
loop. Depending on the specific details, this might simply mean
that the FE converter’s transient response is slightly more oscil-
latory, or it may cause the entire system to be unstable.
For the ADDC02828SA, LP is approximately 1 µH and CP is
approximately 4 µF. Figure 8 shows a more accurate depiction
of the input impedance of the converter as a function of fre-
quency. The negative resistance is, itself, a very good incremen-
tal model for the power state of the converter for frequencies
into the several kHz range.
NAVMAT DERATING
NAVMAT is a Navy power supply reliability manual that is
frequently cited by specifiers of power supplies. A key section of
NAVMAT P4855-1A discusses guidelines for derating designs
and their components. The two key derating criteria are voltage
derating and power derating. Voltage derating is done to reduce
the possibility of electrical breakdown, whereas power derating
is done to maintain the component material below a specified
maximum temperature. While power deratings are typically
stated in terms of current limits (e.g., derate to x% of maximum
rating), NAVMAT also specifies a maximum junction tem-
perature of the semiconductor devices in a power supply. The
NAVMAT component deratings applicable to the ADDC02828SA
are as follows:
Resistors
80% voltage derating
50% power derating
Capacitors
50% voltage and ripple voltage derating
70% ripple current derating
Transformers and Inductors
60% continuous voltage and current derating
90% surge voltage and current derating
20°C less than rated core temperature
30°C below insulation rating for hot spot temperature
25% insulation breakdown voltage derating
40°C maximum temperature rise
Transistors
50% power derating
60% forward current (continuous) derating
75% voltage and transient peak voltage derating
110°C maximum junction temperature
Diodes (Switching, General Purpose, Rectifiers)
70% current (surge and continuous) derating
65% peak inverse voltage derating
110°C maximum junction temperature
Diodes (Zeners)
70% surge current derating
60% continuous current derating
50% power derating
110°C maximum junction temperature
Microcircuits (Linears)
70% continuous current derating
75% signal voltage derating
110°C maximum junction temperature
The ADDC02828SA can meet all the derating criteria listed
above. However, there are a few areas of the NAVMAT deratings
where meeting the guidelines unduly sacrifices performance of
the circuit. Therefore, the standard unit makes the following
exceptions.
Common-Mode EMI Filter Capacitors: The standard
supply uses 500 V capacitors to filter common-mode EMI.
NAVMAT guidelines would require 1000 V capacitors to meet
the 50% voltage derating (500 V dc input to output isolation),
resulting in less common-mode capacitance for the same space.
In typical electrical power supply systems, where the load
ground is eventually connected to the source ground, common-
mode voltages never get near the 500 V dc rating of the standard
supply. Therefore, a lower voltage rating capacitor (500 V)
was chosen to fit more capacitance in the same space in order
to better meet the conducted emissions requirement of MIL-
STD-461D (CE102). For those applications requiring 250 V
or less of isolation from input to output, the present designs
would meet NAVMAT guidelines.
Switching Transistors: 100 V MOSFETs are used in the
standard unit to switch the primary side of the transformers.
Their nominal off-state voltage meets the NAVMAT derating
guidelines. When the MOSFETs are turned off, however, mo-
mentary spikes occur that reach 100 V. The present generation
of MOSFETs are rated for repetitive avalanche, a condition that
was not considered by the NAVMAT deratings. In the worst
case condition, the energy dissipated during avalanche is 1% of
the device’s rated repetitive avalanche energy. To meet the
NAVMAT derating, 200 V MOSFETs could be used. The
100 V MOSFETs are used instead for their lower on-state resis-
tance, resulting in higher efficiency for the power supply.
NAVMAT Junction Temperatures: The two types of power
deratings (current and temperature) can be independent of one
another. For instance, a switching diode can meet its derating
REV. 0
–11–
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