AFL28XXS.pmd
09/10/02
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1
ADVANCED ANALOG
HIGH RELIABILITY
HYBRID DC/DC CONVERTERS
AFL28XXS SERIES
The AFL Series of DC/DC converters feature high power
density with no derating over the full military tempera-
ture range. This series is offered as part of a complete
family of converters providing single and dual output
voltages and operating from nominal +28 or +270 volt
inputs with output power ranging from 80 to 120 watts.
For applications requiring higher output power, indi-
vidual converters can be operated in parallel. The inter-
nal current sharing circuits assure equal current distri-
bution among the paralleled converters. This series in-
corporates Advanced Analog's proprietary magnetic
pulse feedback technology providing optimum dynamic
line and load regulation response. This feedback sys-
tem samples the output voltage at the pulse width modu-
lator fixed clock frequency, nominally 550 KHz. Multiple
converters can be synchronized to a system clock in the
500 KHz to 700 KHz range or to the synchronization
output of one converter. Undervoltage lockout, primary
and secondary referenced inhibit, soft-start and load
fault protection are provided on all models.
These converters are hermetically packaged in two en-
closure variations, utilizing copper core pins to mini-
mize resistive DC losses. Three lead styles are avail-
able, each fabricated with Advanced Analog's rugged
ceramic lead-to-package seal assuring long term
hermeticity in the most harsh environments.
Description
n
16 To 40 Volt Input Range
n
5,
8
, 9,12,15 and
28
Volts Outputs Available
n
High Power Density - up to 84 W / in3
n
Up To 120 Watt Output Power
n
Parallel Operation with Power Sharing
n
Low Profile (0.380") Seam Welded Package
n
Ceramic Feedthru Copper Core Pins
n
High Efficiency - to 85%
n
Full Military Temperature Range
n
Continuous Short Circuit and Overload
Protection
n
Primary and Secondary Referenced
Inhibit Functions
n
Line Rejection > 40 dB - DC to 50KHz
n
External Synchronization Port
n
Fault Tolerant Design
n
Dual Output Versions Available
n
Standard Military Drawings Available
Features
AFL
28V Input, Single Output
Manufactured in a facility fully qualified to MIL-PRF-
38534, these converters are available in four screening
grades to satisfy a wide range of requirements. The CH
grade is fully compliant to the requirements of MIL-H-
38534 for class H. The HB grade is processed and
screened to the class H requirement, but may not nec-
essarily meet all of the other MIL-PRF-38534 require-
ments, e.g., element evaluation and Periodic Inspection
(P.I.) not required. Both grades are tested to meet the
complete group "A" test specification over the full mili-
tary temperature range without output power deration.
Two grades with more limited screening are also avail-
able for use in less demanding applications. Varia-
tions in electrical, mechanical and screening can
be accommodated. Contact Advanced Analog for
special requirements.
PD - 94460A
2
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AFL28XXS Series
Specifications
Static Characteristics -55C < T
CASE
< +125C, 16V< V
IN
< 40V
unless otherwise specified.
For Notes to Specifications, refer to page 4
ABSOLUTE MAXIMUM RATINGS
Input Voltage
-0.5V to 50V
Soldering Temperature
300C for 10 seconds
Case Temperature
Operating
-55C to +125C
Storage
-65C
to
+135C
Parameter
Group A
Subgroups
Test Conditions
Min
Nom
Max
Unit
INPUT VOLTAGE
Note
6
16 28 40 V
OUTPUT VOLTAGE
AFL2805S
AFL2808S
AFL2809S
AFL2812S
AFL2815S
AFL2828S
AFL2805S
AFL2808S
AFL2809S
AFL2812S
AFL2815S
AFL2828S
1
1
1
1
1
1
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
VIN = 28 Volts, 100% Load
4.95
7.92
8.91
11.88
14.85
27.72
4.90
7.84
8.82
11.76
14.70
27.44
5.0
8.0
9.0
12.0
15.0
28.0
5.05
8.08
9.09
12.12
15.15
28.28
5.10
8.16
9.18
12.24
15.30
28.56
V
V
V
V
V
V
V
V
V
V
V
V
OUTPUT CURRENT
AFL2805S
AFL2808S
AFL2809S
AFL2812S
AFL2815S
AFL2828S
VIN = 16, 28, 40 Volts - Note 6
16.0
10.0
10.0
9.0
8.0
4.0
A
A
A
A
A
A
OUTPUT POWER
AFL2805S
AFL2808S
AFL2809S
AFL2812S
AFL2815S
AFL2828S
Note 6
80
80
90
108
120
112
W
W
W
W
W
W
MAXIMUM CAPACITIVE LOAD
Note
1
10,000
fd
OUTPUT VOLTAGE
TEMPERATURE COEFFICIENT
VIN = 28 Volts, 100% Load - Note 1, 6
-0.015
+0.015
%/C
OUTPUT VOLTAGE REGULATION
AFL2828S
Line
All Others
Line
Load
1, 2, 3
1, 2, 3
1, 2, 3
No Load, 50% Load, 100% Load
VIN = 16, 28, 40 Volts
-70.0
-20.0
-1.0
+70.0
+20.0
+1.0
mV
mV
%
OUTPUT RIPPLE VOLTAGE
AFL2805S
AFL2808S
AFL2809S
AFL2812S
AFL2815S
AFL2828S
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
VIN = 16, 28, 40 Volts, 100% Load,
BW = 10MHz
30
40
40
45
50
100
mVpp
mVpp
mVpp
mVpp
mVpp
mVpp
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3
AFL28XXS Series
Static Characteristics
(Continued)
For Notes to Specifications, refer to page 4
Parameter
Group A
Subgroups
Test Conditions
Min
Nom
Max
Unit
INPUT CURRENT
No
Load
Inhibit
1
Inhibit
2
1
2, 3
1, 2, 3
1, 2, 3
VIN = 28 Volts
IOUT = 0
Pin 4 Shorted to Pin 2
Pin 12 Shorted to Pin 8
80
100
5.0
50
mA
mA
mA
mA
INPUT RIPPLE CURRENT
AFL2805S
AFL2808S
AFL2809S
AFL2812S
AFL2815S
AFL2828S
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
VIN = 28 Volts, 100% Load, BW = 10MHz
60
60
60
60
60
60
mApp
mApp
mApp
mApp
mApp
mApp
CURRENT LIMIT POINT
As a percentage of full rated load
1
2
3
VOUT = 90% VNOM , VIN = 28 Volts
Note 5
115
105
125
125
115
140
%
%
%
LOAD FAULT POWER DISSIPATION
Overload or Short Circuit
1, 2, 3
V
IN
= 28 Volts
33
W
EFFICIENCY
AFL2805S
AFL2808S
AFL2809S
AFL2812S
AFL2815S
AFL2828S
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
V
IN
= 28 Volts, 100% Load
78
79
80
80
81
81
81
82
83
84
85
84
%
%
%
%
%
%
ENABLE INPUTS (Inhibit Function)
Converter Off
Sink
Current
Converter
On
Sink
Current
1, 2, 3
1, 2, 3
Logical Low on Pin 4 or Pin 12
Note 1
Logical High on Pin 4 and Pin 12 - Note 9
Note 1
-0.5
2.0
0.8
100
50
100
V
A
V
A
SWITCHING FREQUENCY
1, 2, 3
500
550
600
KHz
SYNCHRONIZATION INPUT
Frequency Range
Pulse Amplitude, Hi
Pulse Amplitude, Lo
Pulse Rise Time
Pulse Duty Cycle
1, 2, 3
1, 2, 3
1, 2, 3
Note 1
Note 1
500
2.0
-0.5
20
700
10
0.8
100
80
KHz
V
V
nSec
%
ISOLATION
1
Input to Output or Any Pin to Case
(except Pin 3). Test @ 500VDC
100 M
DEVICE WEIGHT
Slight Variations with Case Style
85
gms
MTBF
MIL-HDBK-217F, AIF @ TC = 70C
300
KHrs
4
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AFL28XXS Series
Dynamic Characteristics -55C < T
CASE
< +125C, V
IN
=28V
unless otherwise specified.
Notes to Specifications:
1.
Parameters not 100% tested but are guaranteed to the limits specified in the table.
2.
Recovery time is measured from the initiation of the transient to where V
OUT
has returned to within
1% of V
OUT
at 50% load.
3.
Line transient transition time
100
Sec.
4.
Turn-on delay is measured with an input voltage rise time of between 100 and 500 volts per millisecond.
5.
Current limit point is that condition of excess load causing output voltage to drop to 90% of nominal.
6.
Parameter verified as part of another test.
7.
All electrical tests are performed with the remote sense leads connected to the output leads at the load.
8.
Load transient transition time
10
Sec.
9.
Enable inputs internally pulled high. Nominal open circuit voltage
4.0V
DC
.
Parameter
Group A
Subgroups
Test Conditions
Min
Nom
Max
Unit
LOAD TRANSIENT RESPONSE
AFL2805S Amplitude
Recovery
Amplitude
Recovery
AFL2808S
Amplitude
Recovery
Amplitude
Recovery
AFL2809S
Amplitude
Recovery
Amplitude
Recovery
AFL2812S
Amplitude
Recovery
Amplitude
Recovery
AFL2815S
Amplitude
Recovery
Amplitude
Recovery
AFL2828S
Amplitude
Recovery
Amplitude
Recovery
4, 5, 6
4, 5, 6
4, 5, 6
4, 5, 6
4, 5, 6
4, 5, 6
4, 5, 6
4, 5, 6
4, 5, 6
4, 5, 6
4, 5, 6
4, 5, 6
4, 5, 6
4, 5, 6
4, 5, 6
4, 5, 6
4, 5, 6
4, 5, 6
4, 5, 6
4, 5, 6
4, 5, 6
4, 5, 6
4, 5, 6
4, 5, 6
Note 2, 8
Load Step 50%
100%
Load Step 10%
50%
Load Step 50%
100%
Load Step 10%
50%
Load Step 50%
100%
Load Step 10%
50%
Load Step 50%
100%
Load Step 10%
50%
Load Step 50%
100%
Load Step 10%
50%
Load Step 50%
100%
Load Step 10%
50%
-450
-450
-500
-500
-600
-600
-750
-750
-750
-750
-1200
-1200
450
200
450
400
500
200
500
400
600
200
600
400
750
200
750
400
750
200
750
400
1200
200
1200
400
mV
Sec
mV
Sec
mV
Sec
mV
Sec
mV
Sec
mV
Sec
mV
Sec
mV
Sec
mV
Sec
mV
Sec
mV
Sec
mV
Sec
LINE TRANSIENT RESPONSE
Amplitude
Recovery
Note 1, 2, 3
VIN Step = 16
40 Volts
-500
500
500
mV
Sec
TURN-ON CHARACTERISTICS
Overshoot
Delay
4, 5, 6
4, 5, 6
VIN = 16, 28, 40 Volts. Note 4
Enable 1, 2 on. (Pins 4, 12 high or
open)
0
4
250
10
mV
mSec
LOAD FAULT RECOVERY
Same as Turn On Characteristics.
LINE REJECTION
MIL-STD-461D, CS101, 30Hz to 50KHz
Note 1
40 50 dB
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5
AFL28XXS Series
AFL28XXS Circuit Description
Figure I. AFL Single Output Block Diagram
Figure II. Enable Input Equivalent Circuit
Pin 4 or
Pin 12
1N4148
100K
290K
150K
2N3904
+5.6V
Disable
Pin 2 or
Pin 8
Circuit Operation and Application Information
Inhibiting Converter Output
As an alternative to application and removal of the DC volt-
age to the input, the user can control the converter output
by providing TTL compatible, positive logic signals to either
of two enable pins (pin 4 or 12). The distinction between
these two signal ports is that enable 1 (pin 4) is referenced
to the input return (pin 2) while enable 2 (pin 12) is refer-
enced to the output return (pin 8). Thus, the user has
access to an inhibit function on either side of the isolation
barrier. Each port is internally pulled "high" so that when not
used, an open connection on both enable pins permits nor-
mal converter operation. When their use is desired, a logi-
cal "low" on either port will shut the converter down.
1
DC Input
Enable 1
4
Sync Output
5
6
Sync Input
Case
3
2
Input Return
Input
Filter
Primary
Bias Supply
Control
FB
Output
Filter
Current
Sense
Error
Amp
& Ref
Share
Amplifier
Sense
Amplifier
7
+Output
10
+Sense
11
Share
12
Enable 2
9
-Sense
8
Output Return
The AFL series of converters employ a forward switched
mode converter topology. (refer to Figure I.) Operation of
the device is initiated when a DC voltage whose magnitude
is within the specified input limits is applied between pins 1
and 2. If pin 4 is enabled (at a logical 1 or open) the primary
bias supply will begin generating a regulated housekeeping
voltage bringing the circuitry on the primary side of the
converter to life. A power MOSFET is used to chop the DC
input voltage into a high frequency square wave, applying
this chopped voltage to the power transformer at the nomi-
nal converter switching frequency. Maintaining a DC volt-
age within the specified operating range at the input as-
sures continuous generation of the primary bias voltage.
The switched voltage impressed on the secondary output
transformer winding is rectified and filtered to generate the
converter DC output voltage. An error amplifier on the sec-
ondary side compares the output voltage to a precision
reference and generates an error signal proportional to the
difference. This error signal is magnetically coupled through
the feedback transformer into the controller section of the
converter varying the pulse width of the square wave signal
driving the MOSFET, narrowing the width if the output volt-
age is too high and widening it if it is too low, thereby regulat-
ing the output voltage.
Remote Sensing
Connection of the + and - sense leads at a remotely located
load permits compensation for excessive resistance be-
tween the converter output and the load when their physical
separation could cause undesirable voltage drop. This con-
nection allows regulation to the placard voltage at the point
of application. When the remote sensing feature is not used
the sense leads should be connected to their respective
output terminals at the converter. Figure III. illustrates a
typical remotely sensed application.
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