AHP27015SZES [INFINEON]
HIGH RELIABILITY HYBRID DC/DC CONVERTERS;
| 型号： | AHP27015SZES |
| 厂家： | 
Infineon |
| 描述： | HIGH RELIABILITY HYBRID DC/DC CONVERTERS |
| 文件： | 总12页 (文件大小：233K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
PD-97388
AHP28XXS SERIES
28V Input, Single Output
HIGH RELIABILITY
HYBRID DC/DC CONVERTERS
Description
The AHP Series of DC/DC converters feature high power
density without derating over the full military temperature
range. This series is offered as lower cost alternatives to
the legendary AFL series with improved performance
for new design applications. The AHPs are form, fit and
functional replacement to the AFL series. The new AHP
series offers a full compliment of single and dual output
voltages operating from nominal +28 or +270 volt inputs
with output power ranging from 66 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. Same as the AFL, the
AHP series incorporates International Rectifier'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. Under-voltage lockout, primary and secondary
referenced inhibit, soft-start and load fault protection are
provided on all models. Also included is input over-
voltage protection, a new protection feature unique to
the AHP.
AHP
Features
n 16 To 40 Volt Input Range
n 3.3, 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 Stress and Current Sharing
n Input Over-Voltage Protection
n High Efficiency - to 85%
n Continuous Short Circuit and Overload Protection
n External Synchronization Port
n Remote Sensing Terminals
n Primary and Secondary Referenced
Inhibit Functions
n Line Rejection > 40 dB - DC to 50KHz
n Fault Tolerant Design
n Full Military Temperature Range
n Ceramic Feedthru Copper Core Pins
n Low Profile (0.380") Seam Welded Package
n Dual Output Versions 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 International Rectifier’s
rugged ceramic lead-to-package seal assuring long
term hermeticity in harsh environments.
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-
PRF-38534 for class H. The HB grade is fully processed
and screened to the class H requirement, but does not
have material element evaluated to the class H
requirement. Both grades are tested to meet the
complete group “A” test specification over the full
military temperature range without output power
de-rating. Two grades with more limited screening
are also available for use in less demanding
applications. Variations in electrical, mechanical
and screening can be accommodated. Please
contact IR Santa Clara for special requirements.
www.irf.com
1
04/16/09
AHP28XXS Series
Specifications
ABSOLUTE MAXIMUM RATINGS
Input Voltage
-0.5V to 50V
Soldering Temperature
300°C for 10 seconds
Case Temperature - Operating
Case Temperature - 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
IN
= 28V, 100% Load
OUTPUT VOLTAGE
1
1
1
1
1
1
1
3.27
4.95
7.92
3.30
5.00
8.00
3.33
5.05
8.08
AHP2803R3S
AHP2805S
AHP2808S
AHP2809S
AHP2812S
AHP2815S
AHP2828S
8.91
9.00
9.09
11.88
14.85
27.72
12.00
15.00
28.00
12.12
15.15
28.28
V
AHP2803R3S
AHP2805S
AHP2808S
AHP2809S
AHP2812S
AHP2815S
AHP2828S
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
3.23
4.90
7.84
3.37
5.10
8.16
8.82
9.18
11.76
14.70
27.44
12.24
15.30
28.56
OUTPUT CURRENT
V
IN
= 16, 28, 40V - Note 6
AHP2803R3S
AHP2805S
AHP2808S
AHP2809S
AHP2812S
AHP2815S
AHP2828S
20
16
10
10
A
9.0
8.0
4.0
OUTPUT POWER
Note 6
66
80
80
AHP2803R3S
AHP2805S
AHP2808S
AHP2809S
AHP2812S
AHP2815S
AHP2828S
90
W
108
120
112
MAXIMUM CAPACITIVE LOAD
Note 1
= 28V, 100% Load – Notes 1, 6
10,000
-0.015
µF
OUTPUT VOLTAGE
TEMPERATURE COEFFICIENT
V
+0.015
%/°C
IN
OUTPUT VOLTAGE REGULATION
1, 2, 3
1, 2, 3
No Load, 50% Load, 100% Load
-70
-20
+70
+20
mV
mV
AHP2828S
Line
Line
V
IN
= 16, 28, 40V
All Others
1, 2, 3
-1.0
+1.0
%
Load
OUTPUT RIPPLE VOLTAGE
AHP2803R3S
V
= 16, 28, 40V, 100% Load,
IN
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
30
30
40
40
45
BW = 10MHz
AHP2805S
AHP2808S
AHP2809S
AHP2812S
AHP2815S
AHP2828S
mV
pp
50
100
For Notes to Specifications, refer to page 4
2
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AHP28XXS Series
Static Characteristics (Continued)
Group A
Parameter
INPUT CURRENT
Subgroups
Test Conditions
Min
Nom
Max
Unit
V
= 28V
IN
1
2, 3
1, 2, 3
1, 2, 3
80
100
5.0
50
No Load
I
= 0
OUT
mA
Inhibit 1
Inhibit 2
Pin 4 Shorted to Pin 2
Pin 12 Shorted to Pin 8
INPUT RIPPLE CURRENT
AHP2803R3S
V
= 28V, 100% Load, BW = 10MHz
IN
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
60
60
60
60
60
60
60
AHP2805S
AHP2808S
AHP2809S
AHP2812S
AHP2815S
AHP2828S
mA
pp
CURRENT LIMIT POINT
As a percentage of full rated load
V
V
= 90% V
, V = 28V, Note 5
NOM IN
OUT
1
2
3
115
105
125
125
115
140
%
W
LOAD FAULT POWER
DISSIPATION
Overload or Short Circuit
V
= 28V
IN
1, 2, 3
33
= 28V, 100% Load
EFFICIENCY
AHP2803R3S
AHP2805S
AHP2808S
AHP2809S
AHP2812S
AHP2815S
AHP2828S
IN
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
72
78
79
80
80
81
81
74
81
82
83
84
85
84
%
ENABLE INPUTS
(Inhibit Function)
Converter Off
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
V
µA
V
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
ns
%
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
DEVICE WEIGHT
MTBF
Slight Variations with Case Style
85
g
MIL-HDBK-217F, AIF @ T = 70°C
300
KHrs
C
For Notes to Specifications, refer to page 4
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3
AHP28XXS Series
Dynamic Characteristics -55°C < TCASE < +125°C, VIN=28V unless otherwise specified.
Group A
Subgroups
Test Conditions
Min
Nom
Max
Unit
LOAD TRANSIENT RESPONSE
Note 2, 8
AHP2803R3S / AHP2805S
4, 5, 6
4, 5, 6
Load Step 50% ⇔ 100%
Load Step 10% ⇔ 50%
-450
-450
-500
-500
-600
-600
-750
-750
-750
-750
-1200
-1200
450
200
mV
µs
Amplitude
Recovery
4, 5, 6
4, 5, 6
450
400
mV
µ
s
Amplitude
Recovery
⇔
AHP2808S
AHP2809S
AHP2812S
AHP2815S
AHP2828S
Amplitude
Recovery
4, 5, 6
4, 5, 6
Load Step 50%
100%
500
200
mV
µs
4, 5, 6
4, 5, 6
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%
500
400
mV
µs
Amplitude
Recovery
4, 5, 6
4, 5, 6
600
200
mV
µ
s
Amplitude
Recovery
4, 5, 6
4, 5, 6
600
400
mV
µs
Amplitude
Recovery
4, 5, 6
4, 5, 6
750
200
mV
µs
Amplitude
Recovery
4, 5, 6
4, 5, 6
750
400
mV
µ
s
Amplitude
Recovery
4, 5, 6
4, 5, 6
750
200
mV
µs
Amplitude
Recovery
4, 5, 6
4, 5, 6
750
400
mV
µs
Amplitude
Recovery
4, 5, 6
4, 5, 6
1200
200
mV
µ
s
Amplitude
Recovery
4, 5, 6
4, 5, 6
1200
400
mV
µs
Amplitude
Recovery
LINE TRANSIENT RESPONSE
Note 1, 2, 3
-500
500
500
mV
µs
Amplitude
Recovery
⇔
40V
V
Step = 16
IN
TURN-ON CHARACTERISTICS
V
= 16, 28, 40V. Note 4
IN
Overshoot
Delay
4, 5, 6
4, 5, 6
Enable 1, 2 on. (Pins 4, 12 high or
open)
12
10
%
ms
0
4.0
50
LOAD FAULT RECOVERY
LINE REJECTION
Same as Turn On Characteristics.
MIL-STD-461D, CS101, 30Hz to 50KHz
Note 1
40
dB
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 has returned to within ±1% of
OUT
V
OUT
at 50% load.
3. Line transient transition time ≥ 100 µs.
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 µs.
9. Enable inputs internally pulled high. Nominal open circuit voltage ≈ 4.0VDC.
4
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AHP28XXS Series
AHP28XXS Circuit Description
Figure I. AHP 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
Inhibiting Converter Output
Circuit Operation and Application Information
The AHP 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 nominal
converter switching frequency. Maintaining a DC voltage
within the specified operating range at the input assures
continuous generation of the primary bias voltage.
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 generate the
converter DC 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 MOSFET, narrowing the width if the output voltage
is too high and widening it if it is too low, thereby regulating
the output voltage.
Figure II. Enable Input Equivalent Circuit
+5.6V
100K
1N4148
Pin 4 or
Pin 12
Disable
290K
2N3904
200K
Remote Sensing
Pin 2 or
Pin 8
Connection of the + and - sense leads at a remotely located
load permits compensation for excessive resistance
between the converter output and the load when their
physical separation could cause undesirable voltage drop.
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 remotely sensed application.
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 standby current. (See specification table).
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5
AHP28XXS Series
Synchronization of Multiple Converters
When operating multiple converters, system requirements
often dictate operation of the converters at a common
frequency. To accommodate this requirement, the AHP
series converters provide both a synchronization input and
a synchronization output.
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.
The sync output signal is a continuous pulse train set at 550
±50 KHz, with a duty cycle of 15 ±5%. This signal is refer-
enced to the input return and has been tailored to be com-
patible with the AHP 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.
The sync input port permits synchronization of an AHP
connverter 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 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.
Figure III. Preferred Connection for Parallel Operation
1
12
Power
Input
Enable 2
Vin
Rtn
Share
+ Sense
- Sense
Return
Case
AHP
Enable 1
Sync Out
Sync In
+ Vout
7
6
1
Optional
Synchronization
Connection
Share
Bus
12
Enable 2
Vin
Rtn
Share
Case
+ Sense
AHP
AHP
Enable 1
Sync Out
Sync In
- Sense
Return
+ Vout
to Load
6
1
7
12
Enable 2
Share
Vin
Rtn
Case
+ Sense
- Sense
Return
+ Vout
Enable 1
Sync Out
Sync In
6
7
(Other Converters)
ParallelOperation-CurrentandStressSharing
AHP 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.
Figure III. illustrates the preferred connection scheme for
operation of a set of AHP 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 AHP. An important feature of
6
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AHP28XXS 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 outputs erature rise (∆T) above ambient temperature is given by
the following expression:
should be connected to the load with equal lengths of wire of
the same gauge and 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 output and return pins connected at a star
point which is located as 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 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
total output current to +2.20v at full load.
⎧
⎨
⎩
⎫
⎭
1
⎬
−1
P = Device dissipation in Watts = POUT
Eff
As an example, it is desired to maintain the case temperature
of an AHP2815S 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
technological concepts, the AHP 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.
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
⎧
⎨
⎫
⎭
1
⎩.83
⎬
(
)
P = 120•
− 1 = 120• 0.205 = 24.6W
and the required heat sink area is
−1.43
⎧
⎨
⎩
⎫
⎬
⎭
60
2
A
HEAT SINK
=
− 3.0 = 71in
Because the 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
0.85
80 • 24.6
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
ambient. A flat aluminum plate, 0.25" thick and of
approximate dimension 4" by 9" (36 in 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.
2
1
trade name of Sil-Pad® 400 . This particular product is an
2
insulator but electrically conductive versions are also
available. Use of these materials assures maximum surface
contact with the heat 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 can be somewhat messy to use.
1
Sil-Pad is a registered Trade Mark of Bergquist, Minneapolis, MN
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7
AHP28XXS Series
Input Filter
The AHP28XXS series converters incorporate a single stage
LC input filter whose elements dominate the input load
impedance characteristic during the turn-on. The input circuit
is as shown in Figure IV.
⎡
⎢
⎣
⎤
⎥
⎦
VNOM
RADJ = 1000⋅
VOUT −VNOM − 0.25
Figure IV. Input Filter Circuit
For VNOM < VOUT < (VNOM + 0.25V), a resistor is connected
between the +Sense and +Output pins with the –Sense
connected to the output return as shown in Figure VI.
The resistor value (RADJ) is calculated as follows:
3.5µH
Pin 1
1000
RADJ
=
11.2 µfd
⎛
⎞
0.25
⎜
⎜
⎟
⎟
− 1
Pin 2
VOUT −VNOM
⎝
⎠
VNOM = device nominal output voltage
VOUT = desired output voltage
Input Over-Voltage Protection
One additional protection feature is incorporated into the
AHP input circuit. It is an input over-voltage protection. The
output will shutdown and restart at approximately 110% of
the maximum rated input voltage. This protection feature is
unique to the AHP.
RADJ = value of the external resistor required to
achieve the desired Vout
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.
Undervoltage Lockout
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
hysteresis 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.
Figure V. Connection for VOUT > VNOM+ 0.25V
Enable 2
Share
RADJ
+Sense
Output VoltageAdjust
AHP28XXS
- Sense
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 in the locations as shown in
Figure V or Figure VI depending on the desired output
voltage. The range of adjustment and corresponding range
of resistance values can be determined by use of the
equations presented below.
Return
To Load
+Vout
Figure VI. Connection for VNOM< VOUT < (VNOM+ 0.25V)
Enable 2
Share
RADJ
+Sense
AHP28XXS
- Sense
For (VNOM + 0.25V) < VOUT < (VNOM + 0.5V), a resistor is
connected between the +Sense and Sense pins with
the Sense connected to the output return as shown in
Figure V. The resistor value (RADJ) is calculated as
follows:
Return
To Load
+Vout
8
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AHP28XXS Series
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.
Table 1. Nominal Resistance of Cu Wire
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
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 AHP28XXS
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 ≅ 250mV above nominal device voltage.
2.5 m
Ω
1.6 mΩ
As an example of the effects of parasitic resistance,
consider an AHP2815S operating at full power of 120 W.
From the specification sheet, this device has a minimum
efficiency 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.
The consequence is that if the +sense connection is
unintentionally broken, an AHP28XXS has a fail-safe output
voltage of Vout + 250mV, where the 250mV 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 + 500mV.
This 500mV 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.
By choosing 14 or 16 gauge wire in this example, the
parasitic resistance and resulting voltage drop will be
General Application Information
reduced to 25% or 31% of that with 20 gauge wire.
The AHP28XXS series of converters are capable of
providing 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.
Another potential problem resulting from parasitically induced
voltage drop on the input lines is with regard to the operation
of the enable 1 port. The minimum and maximum 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 levels. In Figure VII, it can be seen
that referred to system ground, the voltage on the input
In applications requiring high static currents and large
transients, 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
directly across the input terminals to assure an adequately
low impedance at the input terminals. Table I relates nominal
resistance values and selected wire sizes.
return pin is given by
eRtn = IRtn • RP
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9
AHP28XXS Series
Incorporation of a 100 µfd capacitor at the input terminals
is recommended as compensation for the dynamic effects
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.
Therefore, the logic signal level generated in the system
must be capable of a TTL logic high plus sufficient additional
amplitude to overcome eRtn. When the converter is inhibited,
I
Rtn diminishes to near zero and eRtn will then be at system
ground.
Figure VII. Problems of Parasitic Resistance in input Leads
(See text)
Rp
Rp
Iin
Vin
100
µfd
esource
Rtn
eRtn
IRtn
Case
Enable 1
Sync Out
Sync In
System Ground
10
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AHP28XXS Series
AHP28XXS Case Outlines
Case X
Case W
Pin Variation of Case Y
3.000
2.760
ø 0.128
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
ø 0.040
0.220
2.500
0.220
2.800
0.525
2.975 max
0.238 max
0.42
0.380
Max
0.380
Max
Case Y
Case Z
Pin Variation of Case Y
1.150
0.300
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
ø 0.040
0.220
0.220
1.750
2.500
0.375
0.36
2.800
0.525
2.975 max
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
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11
AHP28XXS Series
Available Screening Levels and Process Variations for AHP28XXS 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
2017
1010
Temperature Cycle
Constant Acceleration
Burn-in
Cond B
500g
Cond C
3000g
Cond C
3000g
2001, Y1 Axis
1015
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
* per Commercial Standards
AHP28XXS Pin Designation
Part Numbering
AHP 28 05 S X / CH
Pin No.
Designation
Screening Level
ES, HB, CH
Blank = min screening
1
2
Positive Input
Input Return
Case
Model
Input Voltage
28 = 28V
270 = 270V
3
Case Style
W, X, Y, Z
4
Enable 1
Output Voltage
05 = 5V, 08 = 8V
09 = 9V, 12 = 12V
15 = 15V, 28 = 28V
Outputs
S = Single
D = Dual
5
Sync Output
Sync Input
Positive Output
Output Return
Return Sense
Positive Sense
Share
6
7
8
9
10
11
12
Enable 2
WORLD HEADQUARTERS: 233 Kansas St., El Segundo, California 90245, Tel: (310) 322 3331
IR SANTA CLARA: 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. 04/2009
12
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