ETC AFL27003.3SY

LAMBDA ADVANCED ANALOG INC.
λ
PRELIMINARY
AFL27003.3S Series
Single Output, Hybrid - High Reliability
DC/DC Converter
DESCRIPTION
FEATURES
The AFL Series of DC/DC converters feature high
power density with no derating over the full military
temperature range. This series is offered as part of
a complete family of converters providing single and
dual output voltages and operating from nominal
+28, +50, +120 or +270 volt inputs with output
power ranging from 80 to 120 watts.
For
applications requiring higher output power, multiple
converters can be operated in parallel. The internal
current sharing circuits assure equal current
distribution among the paralleled converters. This
series incorporates Lambda Advanced Analog's
proprietary magnetic pulse feedback technology
providing optimum dynamic line and load regulation
response. This feedback system samples the output
voltage at the pulse width modulator 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.
n
160 To 400 Volt Input Range
n
3.3 Volt Output
n
High Power Density - 50 W / in3
n
66 Watt Output Power
n
Parallel Operation with Stress and Current
Sharing
n
Low Profile (0.380") Seam Welded Package
n
Ceramic Feedthru Copper Core Pins
n
High Efficiency - 72%
n
Full Military Temperature Range
n
Continuous Short Circuit and Overload
Protection
n
Remote Sensing Terminals
n
Primary and Secondary Referenced Inhibit
Functions
n
Line Rejection > 60 dB - DC to 50KHz
n
External Synchronization Port
n
Fault Tolerant Design
n
Dual Output Versions Available
n
Standard Military Drawings Available
These converters are hermetically packaged in two
enclosure variations, utilizing copper core pins to
minimize resistive DC losses. Three lead styles are
available, each fabricated with Lambda Advanced
Analog's rugged ceramic lead-to-package seal
assuring long term hermeticity in the most harsh
environments.
Manufactured in a facility fully qualified to MIL-PRF38534, 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-PRF-38534 for class H.
The HB grade is processed and screened to the
class H requirement, but may not necessarily meet
all of the other requirements, e.g., element
evaluation and Periodic Inspections (P.I.) not
required. Both grades are tested to meet the
complete group "A" test specification over the full
military temperature range without output power
deration. Two grades with more limited screening
are also available for use in less demanding
applications. Variations in electrical, mechanical
and screening can be accommodated. Contact
Lambda Advanced Analog for special requirements.
SPECIFICATIONS
AFL27003.3S
ABSOLUTE MAXIMUM RATINGS
Input Voltage
Soldering Temperature
Case Temperature
-0.5V to 500V
300°C for 10 seconds
Operating-55°C to +125°C
Storage -65°C to +135°C
TABLE I. Electrical Performance Characteristics.
Test
Symbol
Conditions
-55°C ≤ TC ≤ +125°C
VIN = 28 V dc ±5%, CL = 0
unless otherwise specified
Group A
Subgroups
Device
Type
Limits
Min
3.27
Output voltage
VOUT
IOUT = 0
1
Unit
Max
3.33
01
V
3.23
2,3
3.37
20
Output current 6/
IOUT
VIN = 16, 28, 40 v dc
1,2,3
01
A
Output ripple voltage
VRIP
VIN = 16, 28, 40 v dc
B.W.= 20 Hz to 10 MHz
1,2,3
01
30
Line regulation
VRLINE
VIN = 16, 28, 40 v dc
1,2,3
01
± 10
mV
1,2,3
01
± 35
mV
1
01
15
mA
MV p-p
IOUT = 0, 10 A, and 20 A
Load regulation
VRLOAD
VIN = 16, 28, 40 v dc
IOUT = 0, 10 A, and 20 A
Input current
Input ripple current
IN
IRIP
IOUT = No load
2,3,
17
Inhibit 1, (pin 4) shorted to input
return (pin 2)
Inhibit 2, (pin 12) shorted to output
return (pin 8)
1,2,3
3
1,2,3
5
IOUT = 20 A
1,2,3
01
1,2,3
01
72
60
mA p-p
B.W.= 20 Hz to 10 MHz
Efficiency
EFF
IOUT = 20 A
Isolation
ISO
Input to output or any pin to case
(except pin 3) at
500 V dc, TC = +25°C
1
01
100
Maximum
Capacitive load 1/
CL
No effect on dc performance,
4
01
10,000
TC = +25°C
See footnotes at end of table.
2
%
MΩ
µF
AFL27003.3S
TABLE I. Electrical Performance Characteristics - Continued.
Test
Symbol
Conditions
-55°C ≤ TC ≤ +125°C
VIN =28 V dc ±5%, C= 0
unless otherwise specified
Group A
subgroups
Device
type
Limits
Min
Power dissipation load fault
PD
Overload 6/
1,2,3
01
ICL
Max
30
VOUT = 90% VNOM
VIN = 28 V
1
01
115
125
105
125
115
140
%
2
3
FS
IOUT = 20 A
1,2,3
01
500
600
KHz
Sync frequency range
Fsync
IOUT = 20 A
4,5,6
01
500
700
KHz
Output response to step
transient load changes 2/ 8/
VOTLOAD
50% to/from 100%
4,5,6
01
-450
+450
-450
+450
Switching frequency
10% to/from 50%
Recovery time, step
transient load changes 2/ 8/
TTLOAD
50% to/from 100%
4,5,6
01
200
10% to/from 50%
VOTLINE
Input step 16 V to/from 40 V dc,
IOUT = 20 A
4,5,6
01
Recovery time transient step
line changes 1/ 2/ 3/
TTLINE
Input step 16 V to/from 40 V dc,
IOUT = 20 A
4,5,6
Turn on overshoot 4/
VTonOS
IOUT = 0 and 20 A
Turn on delay
TonD
IOUT = 0 and 20 A
4/
MTBF
mV pk
µs
400
Output response to transient
step line changes 1/ 2/ 3/
Load fault recovery
TrLF
MIL-HDBK-217,
AIF @ Tc = 40°C
500
mV pk
01
500
µs
4,5,6
01
250
mV pk
4,5,6
01
50
120
ms
4,5,6
01
50
120
ms
01
300
-500
Notes:
1/
2/
3/
4/
5/
6/
7/
8/
9/
W
30
Short circuit
Current Limit Point 5/
Unit
Parameters not 100% tested but are guaranteed to the limits specified in the table.
Recovery time is measured from the initiation of the transient to where VOUT has returned to within ± 1 percent of VOUT at 50 percent load.
Line transient transition time ≥10 microseconds.
Turn on delay is measured with an input voltage rise time of between 100 and 500 volts per millisecond.
Current limit point is that condition of excess load causing output voltage to drop to 90% of nominal.
Parameter verified as part of another test.
All electrical tests are performed with remote sense leads connected to the output lead at the load.
Input step transition time ≥100 microseconds.
Enable inputs internally pulled high. Nominal open circuit voltage = 4.0VDC.
3
KHrs
AFL27003.3S Case Outlines
Case X
Case W
Pin Variation of Case Y
3.000
ø 0.128
2.760
0.050
0.050
1
12
0.250
0.250
0.200 Typ
Non-cum
6
7
1.260 1.500
1.000
Ref
1.000
Pin
ø 0.040
Pin
ø 0.040
0.220
2.500
0.220
2.800
2.975 max
0.525
0.238 max
0.42
0.380
Max
0.380
Max
Case Y
Case Z
Pin Variation of Case Y
0.300
1.150
ø 0.140
0.25 typ
0.050
0.050
1
12
0.250
0.250
1.000
Ref
1.000
Ref
0.200 Typ
Non-cum
6
7
1.500 1.750 2.00
Pin
ø 0.040
Pin
ø 0.040
1.750
0.220
0.220
0.375
0.36
2.500
2.800
2.975 max
0.525
0.238 max
0.380
Max
0.380
Max
Tolerances, unless otherwise specified:
4
.XX
=
±0.010
.XXX
=
±0.005
AFL27003.3S Pin Designation
Pin No.
Designation
1
Positive Input
2
Input Return
3
Case
4
Enable 1
5
Sync Output
6
Sync Input
7
Positive Output
8
Output Return
9
Return Sense
10
Positive Sense
11
Share
12
Enable 2
Available Screening Levels and Process Variations for AFL 27003.3S Series.
MIL-STD-883
Method
Requirement
Temperature Range
No
Suffix
ES
Suffix
HB
Suffix
CH
Suffix
-20 to +85°C
-55°C to +125°C
-55°C to +125°C
-55°C to +125°C
Element Evaluation
MIL-PRF-38534
ü
ü
ü
1010
Cond B
Cond C
Cond C
Constant Acceleration
2001
500g
Cond A
Cond A
Burn-in
1015
96hrs @ 125°C
160hrs @ 125°C
160hrs @ 125°C
25°C
25°C
-55, +25, +125°C
-55, +25, +125°C
Cond C
Cond A, C
Cond A, C
Cond A, C
¬
ü
ü
ü
Internal Visual
2017
Temperature Cycle
Final Electrical (Group A)
¬
MIL-PRF-38534
& Specification
Seal, Fine & Gross
1014
External Visual
2009
¬ per Commercial Standards
Part Numbering
AFL 270 05 S X / CH
Model
Input Voltage
Screening
Case Style
270 = 270V
28 = 28V
Output Voltage
03.3 = 03.3V, 05 = 5V,
06 = 6V, 09 = 9V
12 = 12V, 15 = 15V
28 = 28V
W, X, Y, Z
Outputs
S = Single
D = Dual
5
– , ES
HB, CH
AFL27000S Circuit Description
Figure I. AFL Single Output Block Diagram
DC INPUT
1
ENABLE 1
4
INPUT
FILTER
OUTPUT
FILTER
PRIMARY
BIAS SUPPLY
7
+ OUTPUT
10
+ SENSE
11
SHARE
12
ENABLE 2
9
- SENSE
8
OUTPUT RETURN
CURRENT
SENSE
SYNC OUTPUT
5
SHARE
CONTROL
SYNC INPUT
ERROR
AMP
& REF
6
FB
CASE
INPUT RETURN
AMPLIFIER
SENSE
AMPLIFIER
3
2
load when they are physically separated by a
significant distance.
This connection 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 application.
Circuit Operation and Application Information
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. Two power
MOSFETs used to chop the DC input voltage into a
high frequency square wave, apply this chopped
voltage to the power transformer. As this switching
is initiated, a voltage is impressed on a second
winding of the power transformer which is then
rectified and applied to the primary bias supply.
When this occurs, the input voltage is shut out and
the primary bias voltage becomes exclusively
internally generated.
Inhibiting Converter Output
As an alternative to application and removal of the
DC voltage 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
referenced 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 normal converter
operation. When their use is desired, a logical "low"
on either port will shut the converter down.
The switched voltage impressed on the secondary
output transformer winding is rectified and filtered to
provide the converter output voltage. An error
amplifier on the secondary 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 MOSFETs, narrowing the
width if the output voltage is too high and widening it
if it is too low.
Figure II. Enable Input Equivalent Circuit
+5.6V
Pin 4 or
Pin 12
1N4148
100K
Disable
290K
2N3904
Remote Sensing
150K
Pin 2 or
Pin 8
Connection of the + and - sense leads at a remotely
located load permits compensation for resistive
voltage drop between the converter output and the
6
Internally, these ports differ slightly in their function.
In use, a low on Enable 1 completely shuts down all
circuits in the converter while a low on Enable 2
shuts down the secondary side while altering the
controller duty cycle to near zero. Externally, the
use of either port is transparent save for minor
differences in idle current. (See specification table).
low level of +0.8 volts and a minimum high level of
+2.0 volts. The sync output of another converter
which has been designated as the master oscillator
provides a convenient frequency source for this
mode of operation. When external synchronization
is not required, the sync in pin should be left
unconnected thereby permitting the converter to
operate at its' own internally set frequency.
Synchronization of Multiple Converters
The sync output signal is a continuous pulse train
set at 550 ±50 KHz, with a duty cycle of 15 ±5%.
This signal is referenced to the input return and has
been tailored to be compatible with the AFL sync
input port. Transition times are less than 100 ns and
the low level output impedance is less than 50
ohms. This signal is active when the DC input
voltage is within the specified operating range and
the converter is not inhibited. This output has
adequate drive reserve to synchronize at least five
additional converters. A typical synchronization
connection option is illustrated in Figure III.
When operating multiple converters, system
requirements often dictate operation of the
converters at a common frequency.
To
accommodate this requirement, the AFL series
converters provide both a synchronization input and
output.
The sync input port permits synchronization of an
AFL converter to any compatible external frequency
source operating between 500 and 700 KHz. This
input signal should be referenced to the input return
and have a 10% to 90% duty cycle. Compatibility
requires transition times less than 100 ns, maximum
Figure III. Preferred Connection for Parallel Operation
Power
Input
1
12
Vin
Enable 2
Rtn
Share
Case
Enable 1
Optional
Synchronization
Connection
AFL
+ Sense
- Sense
Sync Out
Return
Sync In
+ Vout
6
7
1
12
Share Bus
Enable 2
Vin
Rtn
Share
Case
Enable 1
AFL
+ Sense
- Sense
Sync Out
Return
Sync In
+ Vout
to Load
7
6
1
12
Enable 2
Vin
Rtn
Share
Case
Enable 1
AFL
+ Sense
- Sense
Sync Out
Return
Sync In
+ Vout
7
6
(Other Converters)
Parallel Operation — Current and Stress Sharing
permits equal sharing of a load current exceeding
the capacity of an individual AFL among the
members of the set. An important feature of the
AFL series operating in the parallel mode is that in
addition to sharing the current, the stress induced by
Figure III. illustrates the preferred connection
scheme for operation of a set of AFL converters with
outputs operating in parallel. Use of this connection
7
dissipater thereby compensating for any minor
surface variations. While other available types of
heat conductive materials and thermal compounds
provide similar effectiveness, these alternatives are
often less convenient and are frequently messy to
use.
temperature will also be shared. Thus if one
member of a paralleled set is operating at a higher
case temperature, the current it provides to the load
will be reduced as compensation for the
temperature induced stress on that device.
When operating in the shared mode, it is important
that symmetry of connection be maintained as an
assurance of optimum load sharing performance.
Thus, converter outputs should be connected to the
load with equal lengths of wire of the same gauge
and sense leads from each converter should be
connected to a common physical point, preferably at
the load along with the converter output and return
leads. All converters in a paralleled set must have
their share pins connected together.
This
arrangement is diagrammatically illustrated in Figure
III. showing the outputs and sense pins connected
at a star point which is located close as possible to
the load.
A conservative aid to estimating the total heat sink
A
surface area ( HEAT SINK) required to set the
maximum case temperature rise (∆T) above
ambient temperature is given by the following
expression:
 ∆T 
A HEAT SINK ≈ 
0.85 
80 P 
−1.43
− 3.0
where
∆T = Case temperature rise above ambient
 1

P = Device dissipation in Watts = POUT 
− 1
 Eff

As a consequence of the topology utilized in the
current sharing circuit, the share pin may be used
for other functions. In applications requiring only a
single converter, the voltage appearing on the share
pin may be used as a “current monitor”. The share
pin open circuit voltage is nominally +1.00v at no
load and increases linearly with increasing output
current to +2.20v at full load.
As an example, it is desired to maintain the case
temperature of an AFL27015S at ≤ +85°C in an area
where the ambient temperature is held at a constant
+25°C; then
∆T = 85 - 25 = 60°C.
From the Specification Table, the worst case full
load efficiency for this device is 83%; therefore the
power dissipation at full load is given by
Thermal Considerations
Because of the incorporation of many innovative
technological concepts, the AFL series of converters
is capable of providing very high output power from
a package of very small volume. These magnitudes
of power density can only be obtained by combining
high circuit efficiency with effective methods of heat
removal from the die junctions. This requirement
has been effectively addressed inside the device;
but when operating at maximum loads, a significant
amount of heat will be generated and this heat must
be conducted away from the case. To maintain the
case temperature at or below the specified
maximum of 125°C, this heat must be transferred by
conduction to an appropriate heat dissipater held in
intimate contact with the converter base-plate.
 1

P = 120 • 
− 1 = 120 • ( 0.205) = 24.6W
 .83 
and the required heat sink area is

−1.43
60


− 3.0 = 71 in 2
A HEAT SINK =
 80 • 24.6 0.85 
Thus, a total heat sink surface area (including fins, if
any) of 71 in2 in this example, would limit case rise
to 60°C above ambient. A flat aluminum plate, 0.25"
thick and of approximate dimension 4" by 9" (36 in2
per side) would suffice for this application in a still
air environment. Note that to meet the criteria in
this example, both sides of the plate require
unrestricted exposure to the ambient air.
Because effectiveness of this heat transfer is
dependent on the intimacy of the baseplate-heatsink
interface, it is strongly recommended that a high
thermal conductivity heat transferring medium is
inserted between the baseplate and heatsink. The
material most frequently utilized at the factory during
all testing and burn-in processes is sold under the
1
trade name od Sil-PadR 400 . This particular
product is an insulator but electrically conductive
versions are also available. Use of these materials
assures maximum surface contact with the heat
1 Sil-Pad is a registered Trade Mark of Bergquist, Minneapolis, MN
8
Input Filter
Finding a resistor value for a particular output
voltage, is simply a matter of substituting the
desired output voltage and the nominal device
voltage into the equation and solving for the
corresponding resistor value.
The AFL27000S series converters incorporate a
single stage LC input filter whose elements
dominate the input load impedance characteristic
during the turn-on sequence. The input circuit is as
shown in Figure IV.
Figure V. Connection for VOUT Adjustment
Figure IV. Input Filter Circuit
Enable 2
Share
8.4µH
RADJ
AFL270xxS
Pin 1
+ Sense
- Sense
Return
To Load
0.54µfd
+ Vout
Caution: Do not set Radj < 500Ω
Pin 2
Attempts to adjust the output voltage to a value
greater than 120% of nominal should be avoided
because of the potential of exceeding internal
component stress ratings and subsequent operation
to failure.
Under no circumstance should the
external setting resistor be made less than 500Ω.
By remaining within this specified range of values,
completely safe operation fully within normal
component derating is assured.
Undervoltage Lockout
A minimum voltage is required at the input of the
converter to initiate operation. This voltage is set to
140 ± 5 volts. To preclude the possibility of noise or
other variations at the input falsely initiating and
halting converter operation, a hysteresis of
approximately 10 volts is incorporated in this circuit.
Thus if the input voltage droops to 130 ± 5 volts, the
converter will shut down and remain inoperative
until the input voltage returns to ≈ 140 volts.
Examination of the equation relating output voltage
and resistor value reveals a special benefit of the
circuit topology utilized for remote sensing of output
voltage in the AFL270xxS series of converters. It is
apparent that as the resistance increases, the output
voltage approaches the nominal set value of the
device. In fact the calculated limiting value of
output voltage as the adjusting resistor becomes
very large is ≅ 25mV above nominal device voltage.
Output Voltage Adjust
In addition to permitting close voltage regulation of
remotely located loads, it is possible to utilize the
converter sense pins to incrementally increase the
output voltage over a limited range. The
adjustments made possible by this method are
intended as a means to “trim” the output to a voltage
setting for some particular application, but are not
intended to create an adjustable output converter.
These output voltage setting variations are obtained
by connecting an appropriate resistor value between
the +sense and -sense pins while connecting the sense pin to the output return pin as shown in Figure
V. below.
The range of adjustment and
corresponding range of resistance values can be
determined by use of the equation presented below.
Radj
The consequence is that if the +sense connection is
un-intentionally broken, an AFL270xxS has a failsafe output voltage of Vout + 25mV, where the
25mV is independent of the nominal output voltage.
It can be further demonstrated that in the event of
both the + and - sense connections being broken,
the output will be limited to Vout + 440mV. This 440
mV is also essentially constant independent of the
nominal output voltage. While operation in this
condition is not damaging to the device, not all
performance parameters will be met.
Performance Data


VNOM

= 100 • 
VOUT - VNOM -.025 
Typical performance data is graphically presented
on the following pages for selected parameters on a
variety of AFL270xxS type converters. The data
presented was selected as representative of more
critical parameters and for general interest in typical
converter applications.
Where VNOM = device nominal output voltage, and
VOUT = desired output voltage
9
Lambda Advanced Analog
The information in this data sheet has been carefully checked and is believed to be accurate; however no
responsibility is assumed for possible errors. These specifications are subject to change without notice.
LAMBDA ADVANCED ANALOG INC.
λ
MIL-PRF-38534 Qualified
ISO9001 Registered
10
9849
2270 Martin Avenue
Santa Clara CA 95050-2781
(408) 988-4930 FAX (408) 988-2702