AFL2828SZ/CHB [INFINEON]
DC-DC Regulated Power Supply Module,;
| 型号： | AFL2828SZ/CHB |
| 厂家： | 
Infineon |
| 描述： | DC-DC Regulated Power Supply Module, 电源电路 |
| 文件： | 总11页 (文件大小：115K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
PD - 94460A
AFL28XXS SERIES
28V Input, Single Output
ADVANCED ANALOG
HIGH RELIABILITY
HYBRID DC/DC CONVERTERS
Description
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.
AFL
Features
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 / in
3
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
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.
n Dual Output Versions Available
n Standard Military Drawings Available
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.
www.irf.com
1
09/10/02
AFL28XXS Series
Specifications
ABSOLUTE MAXIMUM RATINGS
Input Voltage
-0.5V to 50V
Soldering Temperature
Case Temperature
300°C for 10 seconds
Operating
Storage
-55°C to +125°C
-65°C to +135°C
Static Characteristics -55°C < TCASE < +125°C, 16V< VIN < 40V unless otherwise specified.
Group A
Parameter
INPUT VOLTAGE
Subgroups
Test Conditions
Min
Nom
Max
Unit
Note 6
16
28
40
V
V
= 28 Volts, 100% Load
OUTPUT VOLTAGE
IN
1
1
1
1
1
1
4.95
7.92
8.91
11.88
14.85
27.72
5.0
8.0
9.0
12.0
15.0
28.0
5.05
8.08
9.09
12.12
15.15
28.28
V
V
V
V
V
V
AFL2805S
AFL2808S
AFL2809S
AFL2812S
AFL2815S
AFL2828S
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
4.90
7.84
8.82
11.76
14.70
27.44
5.10
8.16
9.18
12.24
15.30
28.56
V
V
V
V
V
V
AFL2805S
AFL2808S
AFL2809S
AFL2812S
AFL2815S
AFL2828S
V
= 16, 28, 40 Volts - Note 6
OUTPUT CURRENT
IN
A
A
A
A
A
A
AFL2805S
AFL2808S
AFL2809S
AFL2812S
AFL2815S
AFL2828S
16.0
10.0
10.0
9.0
8.0
4.0
Note 6
OUTPUT POWER
AFL2805S
AFL2808S
AFL2809S
AFL2812S
AFL2815S
AFL2828S
80
80
90
108
120
112
W
W
W
W
W
W
MAXIMUM CAPACITIVE LOAD
Note 1
= 28 Volts, 100% Load - Note 1, 6
10,000
-0.015
µfd
V
+0.015
%/°C
OUTPUT VOLTAGE
TEMPERATURE COEFFICIENT
IN
OUTPUT VOLTAGE REGULATION
1, 2, 3
1, 2, 3
No Load, 50% Load, 100% Load
-70.0
-20.0
+70.0
+20.0
mV
mV
AFL2828S
All Others
Line
Line
V
= 16, 28, 40 Volts
IN
1, 2, 3
-1.0
+1.0
%
Load
V
= 16, 28, 40 Volts, 100% Load,
OUTPUT RIPPLE VOLTAGE
AFL2805S
IN
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
30
40
mV
pp
BW = 10MHz
mV
AFL2808S
AFL2809S
AFL2812S
AFL2815S
AFL2828S
pp
40
mV
pp
45
mV
pp
50
mV
pp
100
mV
pp
For Notes to Specifications, refer to page 4
2
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AFL28XXS Series
Static Characteristics (Continued)
Group A
Parameter
INPUT CURRENT
Subgroups
Test Conditions
= 28 Volts
Min
Nom
Max
Unit
V
IN
1
2, 3
1, 2, 3
1, 2, 3
80
100
5.0
50
mA
mA
mA
mA
No Load
I
= 0
OUT
Inhibit 1
Inhibit 2
Pin 4 Shorted to Pin 2
Pin 12 Shorted to Pin 8
V
= 28 Volts, 100% Load, BW = 10MHz
INPUT RIPPLE CURRENT
AFL2805S
IN
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
60
60
60
60
60
60
mA
pp
mA
mA
mA
mA
mA
AFL2808S
AFL2809S
AFL2812S
AFL2815S
AFL2828S
pp
pp
pp
pp
pp
V
= 90% V
NOM
, V = 28 Volts
IN
CURRENT LIMIT POINT
As a percentage of full rated load
OUT
Note 5
1
2
3
115
105
125
125
115
140
%
%
%
VIN = 28 Volts
LOAD FAULT POWER DISSIPATION
1, 2, 3
33
W
Overload or Short Circuit
EFFICIENCY
AFL2805S
AFL2808S
AFL2809S
AFL2812S
AFL2815S
AFL2828S
VIN = 28 Volts, 100% Load
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
78
79
80
80
81
81
81
82
83
84
85
84
%
%
%
%
%
%
ENABLE INPUTS (Inhibit Function)
Converter Off
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
V
µA
V
Sink Current
Converter On
Sink Current
100
µA
SWITCHING FREQUENCY
1, 2, 3
500
550
600
KHz
SYNCHRONIZATION INPUT
Frequency Range
1, 2, 3
1, 2, 3
1, 2, 3
500
2.0
-0.5
700
10
0.8
100
80
KHz
V
V
nSec
%
Pulse Amplitude, Hi
Pulse Amplitude, Lo
Pulse Rise Time
Note 1
Note 1
20
Pulse Duty Cycle
ISOLATION
1
Input to Output or Any Pin to Case
(except Pin 3). Test @ 500VDC
100
MΩ
Slight Variations with Case Style
85
gms
DEVICE WEIGHT
MTBF
MIL-HDBK-217F, AIF @ T = 70°C
C
300
KHrs
For Notes to Specifications, refer to page 4
www.irf.com
3
AFL28XXS Series
Dynamic Characteristics -55°C < TCASE < +125°C, VIN=28V unless otherwise specified.
Group A
Parameter
Subgroups
Test Conditions
Min
Nom
Max
Unit
Note 2, 8
LOAD TRANSIENT RESPONSE
AFL2805S
AFL2808S
AFL2809S
AFL2812S
AFL2815S
AFL2828S
Amplitude
Recovery
4, 5, 6
4, 5, 6
Load Step 50%
Load Step 10%
100%
50%
-450
-450
450
200
mV
µSec
4, 5, 6
4, 5, 6
mV
µSec
Amplitude
Recovery
450
400
4, 5, 6
4, 5, 6
Load Step 50%
Load Step 10%
100%
50%
-500
-500
mV
µSec
Amplitude
Recovery
500
200
Amplitude
Recovery
4, 5, 6
4, 5, 6
500
400
mV
µSec
600
200
Amplitude
Recovery
4, 5, 6
4, 5, 6
Load Step 50%
Load Step 10%
100%
50%
-600
-600
mV
µ
Sec
600
400
4, 5, 6
4, 5, 6
mV
µSec
Amplitude
Recovery
750
200
4, 5, 6
4, 5, 6
Load Step 50%
Load Step 10%
100%
50%
-750
-750
mV
µSec
Amplitude
Recovery
750
400
Amplitude
Recovery
4, 5, 6
4, 5, 6
mV
µSec
750
200
Amplitude
Recovery
4, 5, 6
4, 5, 6
Load Step 50%
Load Step 10%
100%
50%
-750
-750
mV
µ
Sec
750
400
4, 5, 6
4, 5, 6
mV
µSec
Amplitude
Recovery
1200
200
4, 5, 6
4, 5, 6
Load Step 50%
Load Step 10%
100%
50%
-1200
-1200
mV
µSec
Amplitude
Recovery
1200
400
Amplitude
Recovery
4, 5, 6
4, 5, 6
mV
µSec
LINE TRANSIENT RESPONSE
Note 1, 2, 3
V
Step = 16
40 Volts
-500
500
500
mV
µSec
Amplitude
Recovery
IN
TURN-ON CHARACTERISTICS
V
= 16, 28, 40 Volts. Note 4
IN
Overshoot
Delay
4, 5, 6
4, 5, 6
Enable 1, 2 on. (Pins 4, 12 high or
open)
250
10
mV
mSec
0
4
LOAD FAULT RECOVERY
LINE REJECTION
Same as Turn On Characteristics.
MIL-STD-461D, CS101, 30Hz to 50KHz
Note 1
40
50
dB
Notes to Specifications:
1.
2.
3.
4.
5.
6.
7.
8.
9.
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% of VOUT at 50% load.
Line transient transition time ≥ 100 µSec.
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 the remote sense leads connected to the output leads at the load.
Load transient transition time ≥ 10 µSec.
Enable inputs internally pulled high. Nominal open circuit voltage ≈ 4.0VDC.
4
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AFL28XXS Series
AFL28XXS Circuit Description
Figure I. AFL Single Output Block Diagram
Input
Filter
1
4
5
DC Input
Enable 1
Output
Filter
+Output
+Sense
7
Primary
Bias Supply
10
Current
Sense
Sync Output
Share
Amplifier
11 Share
Control
Error
Amp
& Ref
Sync Input
Case
6
3
2
Enable 2
FB
12
Sense
Amplifier
9
8
-Sense
Input Return
Output Return
output terminals at the converter. Figure III. illustrates a
typical remotely sensed 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. 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.
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-
The switched voltage impressed on the secondary output cal “low” on either port will shut the converter down.
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
Figure II. Enable Input Equivalent Circuit
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
+5.6V
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-
100K
1N4148
Pin 4 or
Pin 12
ing the output voltage.
Disable
290K
Remote Sensing
2N3904
Connection of the + and - sense leads at a remotely located
150K
load permits compensation for excessive resistance be-
tween the converter output and the load when their physical
Pin 2 or
Pin 8
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
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5
AFL28XXS Series
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 second-
ary side while altering the controller duty cycle to near zero.
Externally, the use of either port is transparent to the user
save for minor differences in stndby current. (See specifi-
cation table).
level of +2.0 volts. The sync output of another converter
which has been designated as the master oscillator pro-
vides a convenient frequency source for this mode of op-
eration. When external synchronization is not required,
the sync in pin should be left open (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 con-
verter is not inhibited. This output has adequate drive re-
serve to synchronize at least five additional converters. A
typical connection is illustrated in Figure III.
When operating multiple converters, system requirements
often dictate operation of the converters at a common fre-
quency. To accommodate this requirement, the AFL series
converters provide both a synchronization input and a syn-
chronization output.
The sync input port permits synchronization of an AFL co-
nverter to any compatible external frequency source oper-
ating 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 th an
100 ns, maximum low level of +0.8 volts and a minimum high
Figure III. Preferred Connection for Parallel Operation
1
12
Power
Input
Enable
2
Vin
Rtn
Share
Sense
Sense
Return
Case
Enable
+
-
AFL
AFL
1
Sync Out
Sync In
+
Vout
6
1
7
Optional
Synchronization
Connection
Share Bus
12
Enable
2
Vin
Rtn
Share
Sense
Sense
Return
Case
+
-
Enable
1
Sync Out
Sync In
to Load
+
Vout
7
6
1
12
Enable
2
Vin
Rtn
Share
Sense
Sense
Return
Case
+
-
AFL
Enable
1
Sync Out
Sync In
+
Vout
7
6
(Other Converters)
AFL series operating in the parallel mode is that in addition
to sharing the current, the stress induced by 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.
Parallel Operation-Current and Stress Sharing
Figure III. illustrates the preferred connection scheme for
operation of a set of AFL converters with outputs operating
in parallel. Use of this connection permits equal sharing
among the members of a set whose load current exceeds
the capacity of an individual AFL. An important feature of the
6
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AFL28XXS Series
A conservative aid to estimating the total heat sink surface
When operating in the shared mode, it is important that
symmetry of connection be maintained as an assurance of area (AHEAT SINK) required to set the maximum case temp-
optimum load sharing performance. Thus, converter out- erature rise (∆T) above ambient temperature is given by
the following expression:
puts should be connected to the load with equal lengths of
wire of the same gauge and should be connected to a com-
mon physical point, preferably at the load along with the
converter output and return leads. All converters in a par-
alleled set must have their share pins connected together.
This arrangement is diagrammatically illustrated in Figure
III. showing the output and return pins connected at a star
point which is located close as possible to the load.
1.43
−
∆T
0.85
A
HEAT SINK
≈
− 3.0
80P
where
∆T = Case temperature rise above ambient
As a consequence of the topology utilized in the current
sharing circuit, the share pin may be used for other func-
tions. In applications requiring only a single converter, the
voltage appearing on the share pin may be used as a “cur-
rent monitor”. The share pin open circuit voltage is nomi-
nally +1.00v at no load and increases linearly with increas-
ing total output current to +2.20v at full load.
1
P = Device dissipation in Watts = POUT
Eff
−1
As an example, it is desired to maintain the case tempera-
ture of an AFL2815S at ≤ +85°C while operating in an open
area whose ambient temperature is held at a constant
+25°C; then
Thermal Considerations
∆T = 85 - 25 = 60°C
Because of the incorporation of many innovative techno-
logical 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 effec-
tive methods of heat removal from the die junctions. This
requirement has been effectively addressed inside the de-
vice; 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 tem-
perature 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.
From the Specification Table, the worst case full load effi-
ciency for this device is 83%; therefore the power dissipa-
tion at full load is given by
1
( )
−1 = 120• 0.205 = 24.6W
P = 120•
.83
and the required heat sink area is
1.43
−
60
A
HEAT SINK
=
− 3.0 = 71 in2
80 • 24.60.85
Because the effectiveness of this heat transfer is depen-
dent 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 fac-
tory during all testing and burn-in processes is sold under
Thus, a total heat sink surface area (including fins, if any) of
71 in in this example, would limit case rise to 60°C above
2
ambient. A flat aluminum plate, 0.25" thick and of approxi-
1
the trade name of Sil-Pad 400 . This particular product is
2
mate dimension 4" by 9" (36 in per side) would suffice for
an insulator but electrically conductive versions are also
available. Use of these materials assures maximum sur-
face contact with the heat dissipater thereby compensating
for any minor surface variations. While other available types
of heat conductive materials and thermal compounds pro-
vide similar effectiveness, these alternatives are often less
convenient and can be somewhat messy to use.
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.
1
Sil-Pad is a registered Trade Mark of Bergquist, Minneapolis, MN
www.irf.com
7
AFL28XXS Series
Input Filter
Figure V. Connection for VOUT Adjustment
The AFL28XXS series converters incorporate a two stage
LC input filter whose elements dominate the input load im-
pedance characteristic during the turn-on. The input circuit
is as shown in Figure IV.
Enable
2
Share
Sense
Sense
Return
RADJ
+
-
AFL28xxS
Figure IV. Input Filter Circuit
To Load
+
Vout
900nH
130nH
Pin 1
Pin 2
Note: Radj must be set ≥ 500Ω
Attempts to adjust the output voltage to a value greater than
120% of nominal should be avoided because of the poten-
tial of exceeding internal component stress ratings and sub-
sequent 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 limits
6
µfd
11.2 µfd
Undervoltage Lockout
is assured.
A minimum voltage is required at the input of the converter
to initiate operation. This voltage is set to 14.0 ± 0.5 volts. To
preclude the possibility of noise or other variations at the
input falsely initiating and halting converter operation, a hys-
teresis of approximately 1.0 volts is incorporated in this
circuit. Thus if the input voltage droops to 13.0 ± 0.5 volts,
the converter will shut down and remain inoperative until the
input voltage returns to ≈14.0 volts.
Examination of the equation relating output voltage and re-
sistor value reveals a special benefit of the circuit topology
utilized for remote sensing of output voltage in the AFL28XXS
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.
OutputVoltage Adjust
The consequence is that if the +sense connection is unin-
tentionally broken, an AFL28XXS has a fail-safe output volt-
age 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
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 volt-
age setting variations are obtained by connecting an appro-
priate 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 deter-
output voltage.
General Application Information
The AFL28XXS series of converters are capable of pro-
viding large transient currents to user loads on demand.
Because the nominal input voltage range in this series is
relatively low, the resulting input current demands will be
correspondingly large. It is important therefore, that the line
impedance be kept very low to prevent steady state and
transient input currents from degrading the supply voltage
between the voltage source and the converter input. In
applications requiring high static currents and large tran-
sients, it is recommended that the input leads be made of
adequate size to minimize resistive losses, and that a good
quality capacitor of approximately100µfd be connected di-
mined by use of the following equation.
VNOM
Radj = 100•
VOUT - VNOM -.025
Where VNOM = device nominal output voltage, and
VOUT = desired output voltage
Finding a resistor value for a particular output voltage, is
simply a matter of substituting the desired output voltage rectly across the input terminals to assure an adequately
and the nominal device voltage into the equation and solv-
ing for the corresponding resistor value.
low impedance at the input terminals. Table I relates nomi-
nal resistance values and selected wire sizes.
8
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AFL28XXS Series
Table 1. Nominal Resistance of Cu Wire
Another potential problem resulting from parasitically in-
duced voltage drop on the input lines is with regard to the
operation of the enable 1 port. The minimum and maxi-
mum operating levels required to operate this port are
specified with respect to the input common return line at
the converter. If a logic signal is generated with respect to
a ‘common’that is distant from the converter, the effects of
the voltage drop over the return line must be considered
when establishing the worst case TTL switching levels.
These drops will effectively impart a shift to the logic lev-
els. In Figure VI, it can be seen that referred to system
Wire Size, AWG
Resistance per ft
24 Ga
22 Ga
20 Ga
18 Ga
16 Ga
14 Ga
12 Ga
25.7 mΩ
16.2 mΩ
10.1 m
Ω
6.4 mΩ
4.0 mΩ
2.5 m
Ω
ground, the voltage on the input return pin is given by
1.6 mΩ
As an example of the effects of parasitic resistance, con-
sider an AFL2815S operating at full power of 120 W. From
the specification sheet, this device has a minimum effi-
ciency of 83% which represents an input power of more
than 145 W. If we consider the case where line voltage is at
its’ minimum of 16 volts, the steady state input current
necessary for this example will be slightly greater than 9
amperes. If this device were connected to a voltage source
with 10 feet of 20 gauge wire, the round trip (input and
return) would result in 0.2 Ω of resistance and 1.8 volts of
drop from the source to the converter. To assure 16 volts
at the input, a source closer to 18 volts would be required.
In applications using the paralleling option, this drop will be
multiplied by the number of paralleled devices. By choosing
14 or 16 gauge wire in this example, the parasitic resis-
tance and resulting voltage drop will be reduced to 25% or
eRtn
I
R
•
P
=
Rtn
Therefore, the logic signal level generated in the system
must be capable of a TTL logic high plus sufficient addi-
tional amplitude to overcome eRtn. When the converter is
inhibited, IRtn diminishes to near zero and eRtn will then be at
system ground.
Incorporation of a 100 µfd capacitor at the input terminals
is recommended as compensation for the dynamic ef-
fects of the parasitic resistance of the input cable reacting
with the complex impedance of the converter input, and to
provide an energy reservoir for transient input current
requirements.
31% of that with 20 gauge wire.
Figure VI. Problems of Parasitic Resistance in input Leads
(See text)
Rp
Rp
Iin
Vin
100
µfd
e s o u r c e
Rtn
e R t n
IR t n
Case
Enable 1
Sync Out
Sync In
System Ground
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9
AFL28XXS Series
AFL28XXS Case Outlines
Case X
Case W
Pin Variation of Case Y
3.000
ø
0.128
2.760
0.050
0. 050
0.250
0. 250
1. 000
1.000
Ref
1.260 1.500
0.200 Typ
Non-cum
Pin
ø
0.040
Pin
0.040
0.220
ø
2.500
0. 220
0. 525
2. 800
2.975 max
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
0.250
0.250
1.000
Ref
1.500 1.750 2.00
1.000
Ref
0.200 Typ
Non-cum
Pin
ø
0.040
Pin
0.040
ø
0.220
0.220
1.750
2.500
0.375
0.36
2.800
2.975 max
0.525
0.238 max
0.380
Max
0.380
Max
Tolerances, unless otherwise specified: .XX
.XXX
=
=
±0.010
±0.005
BERYLLIAWARNING: These converters are hermetically sealed;however they contain BeO substrates and should not be ground or subjected to any other
operations including exposure to acids, which may produce Beryllium dust or fumes containing Beryllium
10
www.irf.com
AFL28XXS Series
Available Screening Levels and ProcessVariations for AFL28XXS Series.
MIL-STD-883
Method
No
ES
HB
CH
Requirement
Temperature Range
Element Evaluation
Internal Visual
Suffix
Suffix
Suffix
Suffix
-20°C to +85°C
-55°C to +125°C
-55°C to +125°C
-55°C to +125°C
MIL-H-38534
ü
2017
1010
2001,
1015
¬
ü
Cond B
ü
Temperature Cycle
Constant Acceleration
Burn-in
Cond C
Cond C
500g
Cond A
Cond A
48hrs @ 85°C
48hrs @ 125°C
25°C
160hrs @ 125°C
160hrs @ 125°C
Final Electrical (Group A)
MIL-PRF-38534
Specification
25°C
-55, +25, +125°C -55, +25, +125°C
Seal, Fine & Gross
External Visual
1014
2009
Cond C
Cond A, C
Cond A, C
Cond A, C
¬
ü
ü
ü
* per Commercial Standards
Part Numbering
AFL28XXS Pin Designation
AFL 28 05 S X / CH
Pin No.
Designation
Model
Screening
1
2
Positive Input
Input Return
Case
–
,
ES
Input Voltage
Case Style
W, X, Y, Z
HB, CH
28 = 28V
270 270V
=
3
Output Voltage
05 = 5V, 08 = 8V
09 = 9V, 12 = 12V
15 = 15V, 28 = 28V
Outputs
S = Single
D = Dual
4
Enable 1
5
Sync Output
Sync Input
Positive Output
Output Return
Return Sense
Positive Sense
Share
6
AFL28XXS to Standard Military Drawing Equivalence Table
7
AFL2805S
AFL2808S
AFL2812S
AFL2815S
AFL2828S
5962-9472101
5962-9665901
5962-9472201
5962-9472301
5962-9689901
8
9
10
11
12
Enable 2
WORLD HEADQUARTERS: 233 Kansas St., El Segundo, California 90245, Tel: (310) 322 3331
ADVANCED ANALOG: 2270 Martin Av., Santa Clara, California 95050, Tel: (408) 727-0500
Visit us at www.irf.com for sales contact information.
Data and specifications subject to change without notice. 09/02
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11
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