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ADDC02812DA Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer ADDC02812DA
Beschreibung 28 V/100 W DC/DC Converters with Integral EMI Filter
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 20 Seiten
ADDC02812DA Datasheet, Funktion
a
FEATURES
28 V dc Input, ؎12 V dc @ 8.34 A, 100 W Output
(ADDC02812DA)
28 V dc Input, ؎15 V dc @ 6.68 A, 100 W Output
(ADDC02815DA)
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
28 V/100 W DC/DC Converters
with Integral EMI Filter
ADDC02812DA/ADDC02815DA
FUNCTIONAL BLOCK DIAGRAM
–SENSE
+SENSE
ADJUST
STATUS
VAUX
INHIBIT
SYNC
ISHARE
TEMP
–VIN
+VIN
OUTPUT SIDE
CONTROL
CIRCUIT
INPUT SIDE
CONTROL
CIRCUIT
EMI FILTER
ADDC02812DA/ADDC02815DA
FIXED
FREQUENCY
DUAL
INTERLEAVED
POWER TRAIN
OUTPUT
FILTER
–VOUT
–VOUT
VCOM
VCOM
+VOUT
+VOUT
GENERAL DESCRIPTION
The ADDC02812DA and ADDC02815DA hybrid military dc/
dc converters with integral EMI filter offer the highest power
density of any dc/dc power converters with their features and in
their power range available today. The converters with integral
EMI filter are a fixed frequency, 1 MHz, square wave switching
dc/dc power supply. They are not variable frequency resonant
converters. In addition to many protection features, these con-
verters have system level features that allow them to be used as a
component in larger systems as well as a stand-alone power
supply. The units are designed for high reliability and high
performance applications where saving space and/or weight are
critical.
The ADDC02812DA and ADDC02815DA are available in a
hermetically sealed, molybdenum based hybrid package and are
easily heatsink mountable. Three screening levels are available,
including military SMD.
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
conditions: 16 V–50 V dc; survives low line, high line, and
positive and negative transients
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
REV. A
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: 781/329-4700
World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 1997






ADDC02812DA Datasheet, Funktion
ADDC02812DA/ADDC02815DA
200mV
/DIV
100W
50W
VO
IO
50s
Figure 7. Output Voltage Transient Response to a 50% to
a 100% Step Change in Load with Zero Load Capacitance
(ADDC02812DA)
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
10
100 1k
FREQUENCY – Hz
10k
50k
Figure 10. Audio Susceptibility (Magnitude of VOUT /VIN)
1000
200mV
/DIV
100W
50W
VO
IO
50s
Figure 8. Output Voltage Transient Response to a 50% to
a 100% Step Change in Load with Zero Load Capacitance
(ADDC02815DA)
100
10
1
0.01
0.1 1
10
FREQUENCY – kHz
100
Figure 11. Incremental Output Impedance (Magnitude)
4
UNREGULATED OUTPUT @ 10%
2
0
FULL POWER
–2
10
1
–0.1
VIN = 18V
VIN = 28V
–4
10
30 50 70
% FULL POWER REGULATED OUTPUT
90
Figure 9. Cross Regulation Envelope
–0.01
0.01
0.1 1
10
FREQUENCY – kHz
100
Figure 12. Incremental Input Impedance (Magnitude)
–6– REV. A

6 Page









ADDC02812DA pdf, datenblatt
ADDC02812DA/ADDC02815DA
Incremental Negative Resistance: A POL converter is designed
to hold its output voltage constant no matter how its input volt-
age varies. Given a constant load current, the power drawn from
the input bus is therefore also a constant. If the input voltage
increases by some factor, the input current must decrease by the
same factor to keep the power level constant. In incremental
terms, a positive incremental change in the input voltage results
in a negative incremental change in the input current. The POL
converter therefore looks, incrementally, as a negative resistor.
The value of this negative resistor at a particular operating
point, VIN, IIN, is:
RN
=
VIN
I IN
Note that this resistance is a function of the operating point. At
full load and low input line, the resistance is its smallest, while
at light load and high input line, it is its largest.
Potential System Instability: The preceding analysis assumes
dc voltages and currents. For ac waveforms the incremental input
model for the POL converter must also include the effects of its
input filter and control loop dynamics. When the POL con-
verter is connected to a power source, modeled as a voltage
source, VS, in series with an inductor, LS, and some positive
resistor, RS, the network of Figure 25 results.
RS LS
VS
INPUT
TERMINALS
LP
CP
–|RN|
ADI DC/DC CONVERTER
Figure 25. Model of Power Source and POL Converter
Connection
The network shown in Figure 25 is second order and has the
following characteristic equation:
s2(LS
+
LP
)C
+
s
(LS + LP
–|RN|
)
+
RSCP

+1
=
0
For the power delivery to be efficient, it is required that RS <<
RN. For the system to be stable, however, the following relation-
ship 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 feed-
back 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 ADDC02812DA and ADDC02815DA, LP is approxi-
mately 1 µH and CP is approximately 4 µF. Figure 12 shows a
more accurate depiction of the input impedance of the converter
as a function of frequency. The negative resistance is, itself, a
very good incremental model for the power state of the con-
verter for frequencies into the several kHz range (see Figure 12).
–12–
REV. A

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