IRF AHP2812D High reliability hybrid dc/dc converter Datasheet

PD-97389
AHP28XXD SERIES
28V Input, Dual Output
HIGH RELIABILITY
HYBRID DC/DC CONVERTERS
Description
The AHP 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 or +270 volt inputs with
output power ranging from 80 to 120 watts. For
applications requiring higher output power, individual
converters can be operated in parallel. The internal
current sharing circuits assure equal current distribution
among the paralleled converters. This 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. Undervoltage 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.
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 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-PRF38534 for class H. The HB grade is processed and
screened to the class H requirement, but may not
necessarily meet all of the other MIL-PRF-38534
requirements, 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
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AHP
Features
n
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n
n
n
n
n
n
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16 To 40 Volt Input Range
±5, ±12, and ±15 Volts Outputs Available
High Power Density - up to 70 W / in3
Up To 100 Watt Output Power
Parallel Operation with Stress and Current Sharing
Input Over-Voltage Protection
High Efficiency - to 85%
Continuous Short Circuit and Overload
Protection
External Synchronization Port
Remote Sensing Terminals
Primary and Secondary Referenced
Inhibit Functions
Line Rejection > 40 dB - DC to 50KHz
Fault Tolerant Design
Full Military Temperature Range
Ceramic Feedthru Copper Core Pins
Low Profile (0.380") Seam Welded Package
Single Output Versions Available
full military temperature range without output
power deration. Two grades with more limited
screening are also avail-able for use in less
demanding applications. Variations in electrical,
mechanical and screening can be accommodated.
Contact IR Santa Clara for special requirements.
1
04/16/09
AHP28XXD 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
Subgroups
Parameter
Test Conditions
INPUT VOLTAGE
Note 6
OUTPUT VOLTAGE
VIN = 28V, 100% Load
Positive Output
Negative Output
Positive Output
Negative Output
Positive Output
Negative Output
Positive Output
Negative Output
Positive Output
Negative Output
Positive Output
Negative Output
AHP2805D
AHP2812D
AHP2815D
AHP2805D
AHP2812D
AHP2815D
1
1
1
1
1
1
2, 3
2, 3
2, 3
2, 3
2, 3
2, 3
OUTPUT CURRENT
Nom
Max
Unit
16
28
40
V
4.95
-5.05
11.88
-12.12
14.85
-15.15
4.90
-5.10
11.76
-12.24
14.70
-15.30
5.00
-5.00
12.00
-12.00
15.00
-15.00
5.05
-4.95
12.12
-11.88
15.15
-14.85
5.10
-4.90
12.24
-11.76
15.30
-14.70
V
12.8
6.4
5.3
A
VIN = 16, 28, 40V - Notes 6, 11
Either Output
Either Output
Either Output
AHP2805D
AHP2812D
AHP2815D
OUTPUT POWER
Total of Both Outputs - Notes 6,11
AHP2805D
AHP2812D
AHP2815D
MAXIMUM CAPACITIVE LOAD
Each Output - Note 1
OUTPUT VOLTAGE
TEMPERATURE COEFFICIENT
VIN = 28V, 100% Load - Notes 1, 6
OUTPUT VOLTAGE REGULATION
Line
Load
Min
1, 2, 3
1, 2, 3
Cross
AHP2805D
1, 2, 3
AHP2812D
1, 2, 3
AHP2815D
1, 2, 3
Note 10
No Load, 50% Load, 100% Load
VIN = 16, 28, 40V
VIN = 16, 28, 40V - Note 12
Positive Output
Negative Output
Positive Output
Negative Output
Positive Output
Negative Output
80
96
100
W
10,000
µF
-0.015
+0.015
-0.5
-1.0
+0.5
+1.0
-1.0
-9.0
-1.0
-5.0
-1.0
-5.0
+1.0
+9.0
+1.0
+5.0
+1.0
+5.0
%/°C
%
For Notes to Specifications, refer to page 4
2
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AHP28XXD Series
Static Characteristics (Continued)
Parameter
OUTPUT RIPPLE VOLTAGE
AHP2805D
AHP2812D
AHP2815D
Group A
Subgroups
1, 2, 3
1, 2, 3
1, 2, 3
INPUT CURRENT
No Load
1
2, 3
Inhibit 1
1, 2, 3
Inhibit 2
AHP2805D
AHP2812D
AHP2815D
INPUT RIPPLE CURRENT
AHP2805D
AHP2812D
AHP2815D
CURRENT LIMIT POINT
Expressed as a percentage
of Full Rated Load
LOAD FAULT POWER DISSIPATION
Overload or Short Circuit
ENABLE INPUTS (Inhibit Function)
Converter Off
Sink Current
Converter On
Sink Current
SWITCHING FREQUENCY
SYNCHRONIZATION INPUT
Frequency Range
Pulse Amplitude, Hi
Pulse Amplitude, Lo
Pulse Rise Time
Pulse Duty Cycle
ISOLATION
Min
Nom
VIN = 28V
IOUT = 0
Max
Unit
60
80
80
mVpp
80
100
5.0
Pin 4 Shorted to Pin 2
mA
Pin 12 Shorted to Pin 8
50
30
30
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
1
2
3
1, 2, 3
EFFICIENCY
AHP2805D
AHP2812D
AHP2815D
Test Conditions
VIN = 16, 28, 40V, 100% Load,
BW = 10MHz
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
1, 2, 3
VIN = 28V, 100% Load
VOUT = 90% VNOM, Equal current on
positive and negative outputs - Note 5
115
105
105
VIN = 28V
VIN = 28V, 100% Load
Logical Low on Pin 4 or Pin 12
Note 1
Logical High on Pin 4 and Pin 12 - Note 9
Note 1
78
82
81
2.0
500
1, 2, 3
1, 2, 3
1, 2, 3
500
2.0
-0.5
1
Note 1
Note 1
Input to Output or Any Pin to Case
(except Pin 3). Test @ 500VDC
DEVICE WEIGHT
Slight Variations with Case Style
MTBF
MIL-HDBK-217F, AIF @ TC = 40°C
550
20
100
125
125
125
%
33
W
%
0.8
100
50
100
V
µA
V
µA
600
KHz
700
10
0.8
100
80
KHz
V
V
ns
%
MΩ
85
300
mApp
81
84
85
-0.5
1, 2, 3
60
60
60
g
KHrs
For Notes to Specifications, refer to page 4
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3
AHP28XXD Series
Dynamic Characteristics -55°C < TCASE < +125°C, VIN=28V unless otherwise specified.
Parameter
Group A
Subgroups
AHP2812D
Either Output
AHP2815D
Either Output
Min
Nom
Max
Unit
Notes 2, 8
LOAD TRANSIENT RESPONSE
AHP2805D
Either Output
Test Conditions
Amplitude
Recovery
4, 5, 6
4, 5, 6
Load Step 50% ⇔ 100%
-450
450
200
mV
µs
Amplitude
Recovery
4, 5, 6
4, 5, 6
Load Step 10% ⇔ 50%
10% ⇒ 50%
50% ⇒ 10%
-450
450
200
400
mV
µs
µs
Amplitude
Recovery
4, 5, 6
4, 5, 6
Load Step 50% ⇔ 100%
-750
750
200
mV
µs
Amplitude
Recovery
4, 5, 6
4, 5, 6
Load Step 10% ⇔ 50%
10% ⇒ 50%
50% ⇒ 10%
-750
750
200
400
mV
µs
µs
Amplitude
Recovery
4, 5, 6
4, 5, 6
Load Step 50% ⇔ 100%
-750
750
200
mV
µs
Amplitude
Recovery
4, 5, 6
4, 5, 6
Load Step 10% ⇔ 50%
10% ⇒ 50%
50% ⇒ 10%
-750
750
200
400
mV
µs
µs
-500
500
500
mV
µs
12
10
%
ms
LINE TRANSIENT RESPONSE
Notes 1, 2, 3
VIN Step = 16 ⇔ 40V
Amplitude
Recovery
TURN-ON CHARACTERISTICS
Overshoot
Delay
VIN = 16, 28, 40V - Note 4
4, 5, 6
4, 5, 6
Enable 1, 2 on. (Pins 4, 12 high or
open)
LOAD FAULT RECOVERY
Same as Turn On Characteristics.
LINE REJECTION
MIL-STD-461D, CS101, 30Hz to 50KHz
Note 1
0
4.0
40
50
dB
Notes to Specifications:
1.
2.
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.
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.
10. Load current split equally between +VOUT and -VOUT.
11. Output load must be distributed so that a minimum of 20% of the total output power is being provided by one of
the outputs.
12. Cross regulation measured with load on tested output at 30% of maximum load while changing the load on
other output from 30% to 70%.
4
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AHP28XXD Series
AHP28XXD Circuit Description
Figure I. AFL Dual Output Block Diagram
DC Input
1
Enable 1 4
Input
Filter
Output
Filter
7 + Output
Current
Sense
Primary
Bias Supply
8 Output Return
Output
Filter
Sync Output
5
Sync Input
6
Control
Case
3
Input Return
2
Circuit Operation and Application Information
The AHP series of converters employ a forward switched
mode converter topology. (refer to the block diagram in
Figure I.) Operation of the device is initiated when a DC
voltage whose magnitude is within the specified input voltage
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. By maintaining a DC voltage within specified
operating range at the input, continuous generation of the
bias voltage is assured.
The switched voltage impressed on the secondary output
transformer windings is rectified and filtered to provide the
positive and negative converter output voltages. An error
amplifier on the secondary side compares the positive 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 control section of the converter varying the pulse width
of the square wave signal driving the MOSFETs, narrowing
the pulse width if the output voltage is too high and widening
it if it is too low. These pulse width variations provide the
necessary corrections to regulate the magnitude of output
voltage within its’ specified limits.
Share
Amplifier
Error
Amp
& Ref
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-Output
11 Share
12 Enable 2
10 Trim
series can be initiated by simply applying an input voltage to
pins 1 and 2 and connecting the appropriate loads between
pins 7, 8, and 9. As is the case with any high power density
converter, operation should not be initiated before secure
attachment to an appropriate heat dissipator. (See Thermal
Considerations, page 7) Additional application information
is provided in the paragraphs following.
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.
Figure II. Enable Input Equivalent Circuit
+5.6V
Pin 4 or
Pin 12
1N4148
100K
Disable
270K
Because the primary portion of the circuit is coupled to the
secondary side with magnetic elements, full isolation from
input to output is maintained.
Although incorporating several sophisticated and useful
ancilliary features, basic operation of the AHP28XXD
9
2N3904
200K
Pin 2 or
Pin 8
5
AHP28XXD 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 secondary
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 idle current. (See specification
table).
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
output.
The sync input port permits synchronization of an AHP
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 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 indicated, 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
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 synch output has adequate
drive reserve to synchronize at least five additional
converters. A typical synchronization connection option is
illustrated in Figure III.
Figure III. Preferred Connection for Parallel Operation
Power
Input
1
Vin
Enable 2
Rtn
Case
Share
Enable 1
AHP
Trim
- Output
Return
Sync Out
Optional
Synchronization
Connection
12
+ Output
Sync In
6
7
1
12
Share
Bus
Enable 2
Vin
Rtn
Share
Case
Enable 1
AHP
Sync Out
Trim
to Negative Load
- Output
Return
Sync In
+ Output
7
6
1
Vin
Enable 2
Rtn
Share
Case
Enable 1
AHP
Sync Out
Sync In
6
to Positive Load
12
Trim
- Output
Return
+ Output
7
(Other Converters)
Parallel Operation-Current and Stress Sharing
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 current
sharing among the members of a set whose load current
exceeds the capacity of an individual AHP. An important
6
feature of the 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
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AHP28XXD Series
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 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.
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 “total 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. Note that the
current we refer to here is the total output current, that is,
the sum of the positive and negative outout currents.
Thermal Considerations
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.
Since 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
trade name of Sil-Pad® 4001 . This particular product is an
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.
A conservative aid to estimating the total heat sink surface
area (AHEAT SINK) required to set the maximum case temperature rise (∆T) above ambient temperature is given by
the following expression:
.
⎧ ∆T ⎫−143
⎬
− 3.0
A HEAT SINK ≈ ⎨
⎩ 80P 0.85 ⎭
where
∆T = Case temperature rise above ambient
⎫
⎧ 1
P = Device dissipation in Watts = POUT ⎨
− 1⎬
⎭
⎩ Eff
As an example, assume that it is desired to operate an
AHP2815D in a still air environment where the ambient
temperature is held to a constant +25°C while holding the
case temperature at TC ≤ +85°C; then case temperature
rise is
∆T = 85 - 25 = 60°C
From the Specification Table, the worst case full load
efficiency for AHP2815D is 83% at 100 watts: thus, power
dissipation at full load is given by
⎧ 1
⎫
P = 100 • ⎨ − 1⎬ = 100 • (0.205) = 20.5W
⎩ .83 ⎭
and the required heat sink area is
60
⎧
⎫
A HEAT SINK = ⎨
0.85 ⎬
⎩ 80 • 20.5
⎭
−1.43
− 3.0 = 56.3 in 2
Thus, a total heat sink surface area (including fins, if any) of
56 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 7" (28 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 +25°C ambient
air.
1Sil-Pad is a registered Trade Mark of Bergquist, Minneapolis, MN
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7
AHP28XXD Series
Input Filter
Figure V. Connection for VOUT Adjustment
The AHP28XXD 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.
12
Enable 2
Share
AHP28xxD
Figure IV. Input Filter Circuit
RADJ
Trim
+
- Vout
To
Loads
Return
3.5µH
+ Vout
Pin 1
7
11.2 µfd
Pin 2
Connect Radj to + to increase, - to decrease
Table 1. Output Voltage Trim Values and Limits
AHP2805D
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.
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.
Output Voltage Adjust
By use of the trim pin (10), the magnitude of output voltages
can be adjusted over a limited range in either a positive or
negative direction. Connecting a resistor between the trim
pin and either the output return or the positive output will
raise or lower the magnitude of output voltages. The span
of output voltage adjustment is restricted to the limits shown
in Table I.
AHP2812D
AHP2815D
Vout
Radj
Vout
Radj
Vout
Radj
5.5
5.4
5.3
5.2
5.1
5.0
4.9
4.8
4.7
4.6
4.583
0
12.5K
33.3K
75K
200K
∞
190K
65K
23K
2.5K
0
12.5
12.4
12.3
12.2
12.1
12.0
11.7
11.3
10.8
10.6
10.417
0
47.5K
127K
285K
760K
∞
975K
288K
72.9K
29.9K
0
15.5
15.4
15.3
15.2
15.1
15.0
14.6
14.0
13.5
13.0
12.917
0
62.5K
167K
375K
1.0M
∞
1.2M
325K
117K
12.5K
0
Note that the nominal magnitude of output voltage resides in
the middle of the table and the corresponding resistor value
is set to ∞. To set the magnitude greater than nominal, the
adjust resistor is connected to output return. To set the
magnitude less than nominal, the adjust resistor is connected
to the positive output. (Refer to Figure V.)
For output voltage settings that are within the limits, but
between those listed in Table I, it is suggested that the
resistor values be determined empirically by selection or by
use of a variable resistor. The value thus determined can
then be replaced with a good quality fixed resistor for
permanent installation.
When use of this adjust feature is elected, the user should
be aware that the temperature performance of the converter
output voltage will be affected by the temperature
performance of the resistor selected as the adjustment
element and therefore, is advised to employ resistors with a
tight temperature coefficient of resistance.
8
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AHP28XXD Series
General Application Information
The AHP28XXD 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.
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 2 relates
nominal resistance values and selected wire sizes.
Table 2. Nominal Resistance of Cu Wire
Wire Size, AWG
Resistance per ft
24 Ga
25.7 mΩ
22 Ga
16.2 mΩ
20 Ga
10.1 mΩ
18 Ga
6.4 mΩ
16 Ga
4.0 mΩ
14 Ga
2.5 mΩ
12 Ga
1.6 mΩ
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 1.5 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 resistance
and resulting voltage drop will be reduced to 25% or 31%
of that with 20 gauge wire.
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 VI, it can be seen that referred to system ground,
the voltage on the input return pin is given by
eRtn = IRtn • RP
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,
IRtn diminishes to near zero and eRtn will then be at system
ground.
As an example of the effects of parasitic resistance,
consider an AHP2815D operating at full power of 100 W.
From the specification sheet, this device has a minimum
efficiency of 83% which represents an input power of more
than 120 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 7.5
Amps.
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.
Figure VI. Problems of Parasitic Resistance in input Leads
Rp
esource
Rp
Iin
IRtn
100
µfd
Vin
eRtn
Rtn
Case
System Ground
Enable 1
Sync Out
Sync In
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9
AHP28XXD Series
AHP28XXD 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
6
1.750
1.000
Ref
0.200 Typ
Non-cum
7
1.500 1.750 2.00
Pin
ø 0.040
0.375
Pin
ø 0.040
0.220
0.220
0.36
2.500
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
BERYLLIA WARNING: 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
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AHP28XXD Series
Available Screening Levels and Process Variations for AHP28XXD Series.
MIL-STD-883
Method
Requirement
Temperature Range
No
Suffix
ES
Suffix
HB
Suffix
CH
Suffix
-20°C to +85°C
-55°C to +125°C
-55°C to +125°C
-55°C to +125°C
Element Evaluation
MIL-H-38534
9
9
9
1010
Cond B
Cond C
Cond C
2001, Y1 Axis
500g
3000g
3000g
Internal Visual
2017
Temperature Cycle
Constant Acceleration
Burn-in
‘
1015
48hrs @ 85°C
48hrs @ 125°C
160hrs @ 125°C
160hrs @ 125°C
MIL-PRF-38534
Specification
25°C
25°C
-55, +25, +125°C
-55, +25, +125°C
Seal, Fine & Gross
1014
Cond C
Cond A, C
Cond A, C
Cond A, C
External Visual
2009
‘
9
9
9
Final Electrical (Group A)
* per Commercial Standards
AHP28XXD Pin Designation
Pin No.
Part Numbering
AHP 28 05 D X / CH
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
Negative Output
10
Output Voltage Trim
11
Share
12
Enable 2
Model
Input Voltage
Screening Level
ES, HB, CH
Blank = min screening
28 = 28V
270 = 270V
Case Style
Output Voltage
Outputs
05 = 5V, 12 = 12V
15 = 15V
W, X, Y, Z
S = Single
D = Dual
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
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11
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