40 Watt XT Dual Series DC/DC Converters
Features
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Fully Shielded/Filtered Design
Lowest Noise Outputs, 70 mV P-P
Very Low and Specified Reflected Ripple Current
Very Low I/O Capacitance, 500 pF Typical
Water Washable Shielded Copper Case
5 Year Warranty
Description
These dual output converters are designed for ultra wide input
range low noise telecommunications, industrial, and instrument
applications. The very wide input range (4:1) is ideal for
battery or unregulated input applications while the low noise
complements even the most sensitive analog circuitry.
These converters are state of the art 220 kHz MOSFET
based designs that provide outstanding regulation and
conversion efficiencies of over 85%.
Remote ON/OFF and output voltage trim functions are also
included.
The converters are protected from output shorts to common
by a high speed pulse by pulse digital current limit circuit and
a self resetting thermal overload protection circuit.
As with all CALEX converters the 40 Watt XT Dual series
is covered by our 5 Year Warranty.
Model
24D5.3000XT
24D12.1500XT
24D15.1200XT
48D5.3500XT
48D12.1700XT
48D15.1300XT
Selection Chart
Input Range
VDC
Min
9
9
9
20
20
20
Max
36
36
36
72
72
72
VDC
±5
±12
±15
±5
±12
±15
Output
mA
±3000
±1500
±1200
±3500
±1700
±1300
Power
W
30
36
36
35
41
39
40 Watt XT Dual Series Block Diagram
A
2401 Stanwell Drive • Concord, California 94520 • Ph: 925/687-4411 or 800/542-3355 • Fax: 925/687-3333 • www.calex.com • Email: sales@calex.com
1
3/2001
40 Watt XT Dual Series DC/DC Converters
Input Parameters*
Model
Voltage Range
Input Current Full Load
No Load
Efficiency
Reflected Ripple (1)
Switching Frequency
Maximum Input
Overvoltage,
100ms Maximum
Turn-on Time,
1% Output Error
Recommended Fuse
MIN
MAX
TYP
TYP
TYP
TYP
TYP
TYP
MAX
TYP
40
45
30
30
(2)
40
24D5.3000XT
24D12.1500XT 24D15.1200XT
9
36
1820
20
82
50
10
48D5.3500XT
48D12.1700XT 48D15.1300XT
20
72
1010
15
85
55
7.0
Units
VDC
960
15
85
55
7.0
mA
%
mA P-P
mA RMS
kHz
80
30
30
VDC
ms
AMPS
1550
15
81
80
8.5
1835
20
82
50
10
220
885
15
82
40
6.5
Output Parameters*
Model
Output Voltage
Output Voltage Accuracy
Rated Load Range (3)
Load Regulation:
25% Max Load to
Max Load (4)
Cross Regulation (5)
Line Regulation
Vin = Min-Max VDC
Short Term Stability (6)
Long Term Stability
Noise, Peak - Peak (1)
RMS Noise
Temperature Coefficient
Short Circuit Protection
MIN
TYP
MAX
MIN
MAX
TYP
MAX
TYP
TYP
MAX
TYP
TYP
TYP
TYP
TYP
MAX
130
40
70
15
70
30
50
250
Output to Common and Thermal Protection
24D5.3000XT
±5
4.950
5.000
5.050
0
±3000
0.4
1.0
2.5
24D12.1500XT 24D15.1200XT
±12
11.900
12.000
12.100
0
±1500
0.1
0.5
0.8
0.1
0.2
< 0.05
< 0.1
120
35
130
35
100
30
±15
14.900
15.000
15.100
0
±1200
48D5.3500XT
±5
4.950
5.000
5.050
0
±3500
0.4
1.0
2.5
48D12.1700XT 48D15.1300XT
±12
11.900
12.000
12.100
0
±1700
0.1
0.5
0.8
±15
14.900
15.000
15.100
0
±1300
Units
VDC
VDC
mA
%
%
%
%/24Hrs
%/kHrs
mV P-P
mV RMS
ppm/°C
NOTES
*
(1)
(2)
(3)
(4)
(5)
(6)
All parameters measured at Tc = 25°C, nominal input voltage
and full rated load unless otherwise noted. Refer to the
CALEX Application Notes for the definition of terms,
measurement circuits and other information.
Noise is measured per CALEX application notes. Measurement
bandwidth is 0-20 MHz. RMS noise is measured over a 0.01-1
MHz bandwidth. To simulate standard PCB decoupling practices,
output noise is measured with a 10µf, tantalum and 0.01µF,
ceramic capacitor located 1 inch away from the converter. Input
ripple is measured into a 10µH source impedance.
See our application note for picking the correct fuse size.
The converter may be safely operated at any load from zero to
the full rating. Dynamic response of the converter will degrade
if the converter is operated with less than 25% output load.
Load regulation is defined for loading/unloading both outputs
simultaneously. Load range is 25 to 100%.
Cross regulation is defined for loading/unloading one output
while the other output is kept at full load. Load range is
25 to 100%.
Short term stability is specified after a 30 minute warmup
at full load, constant line and recording the drift over a 24
hour period.
(7)
(8)
Case is tied to the CMN output pin.
The functional temperature range is intended to give an additional
data point for use in evaluating this power supply. At the
low functional temperature the power supply will function with
no side effects, however sustained operation at the high
functional temperature may reduce the expected operational
life. The data sheet specifications are not guaranteed over
the functional temperature range.
(9) The case thermal impedance is specified as the case temperature
rise over ambient per package watt dissipated.
(10) Specifications subject to change without notice.
A
2401 Stanwell Drive • Concord, California 94520 • Ph: 925/687-4411 or 800/542-3355 • Fax: 925/687-3333 • www.calex.com • Email: sales@calex.com
2
3/2001
40 Watt XT Dual Series DC/DC Converters
General Specifications*
All Models
ON/OFF Function
ON Logic Level
or Leave Pin Open
OFF Logic Level
or Tie Pin to -Input
Open Circuit Voltage
Input Resistance
Converter Idle Current
ON/OFF Pin Low
Isolation (7)
Isolation Voltage
Input to Output, 24D
Input to Output, 48D
10µA Leakage
Input to Output
Capacitance
Output Trim Function
Trim Range
Input Resistance
Environmental
Case Operating Range
Case Functional Range (8)
Storage Range
Thermal Shutdown
Case Temperature
Thermal Impedance (9)
Unit Weight
Mounting Options
Chassis Mounting Kit
-I Suffix on Part Number
-HS Suffix on Part Number
MS9
Inserts In Case
Heat Sink Option
MIN
MAX
MIN
MAX
MIN
MAX
TYP
TYP
TYP
-40
85
-55
90
-55
105
100
4.4
7
°C
°C
°C
°C
°C/Watt
oz
Units
MIN
MAX
TYP
TYP
TYP
4
1.0
5
6
7
VDC
VDC
VDC
kohms
mA
MIN
MIN
TYP
700
1544
500
VDC
BOTTOM VIEW
pF
Mechanical tolerances unless otherwise noted:
SIDE VIEW
MIN
MIN
±10
10
%
kohms
X.XX dimensions: ±0.020 inches
X.XXX dimensions: ±0.005 inches
Pin
1
2
3
4
5
6
8
Function
+INPUT
-INPUT
+OUTPUT
CMN
-OUTPUT
TRIM
ON/OFF
Applications Information
You truly get what you pay for in a CALEX converter, a
complete system oriented and specified DC/DC converter -
no surprises, no external noise filtering circuits needed, no
heatsinking problems, just “plug and play”.
The 40 Watt XT Dual series like all CALEX converters
carries the full 5 year CALEX no hassle warranty. We can offer
a five year warranty where others can’t because with CALEX
it’s rarely needed.
Keep reading, you’ll find out why.
Noise has also achieved new lows in this design, while the
industry standard is to specify output noise as 1 to 5% peak
to peak typical with no mention of measurement bandwidth.
The XT converters are fully specified and tested to a wide
bandwidth of 0-20 MHz.
A
Input filtering reduces reflected ripple noise and is similarly
low and also fully specified for typical values (exact value
depends on input voltage range). Typical RMS noise over a 10
kHz to 1 MHz bandwidth is specified for both the input and
output.
Full overload protection is provided by independent pulse-
by-pulse current limiting and an over-temperature shutdown
circuit. These protection features assure you that our XT Dual
will provide you with zero failure rate operation.
Five sided shielding is standard along with specified
operation over the full industrial temperature range of -40 to
+85°C case temperature.
General Information
The XT Dual series is mindful of battery operation for industrial,
medical control and remote data collection applications. The
remote ON/OFF pin places the converter in a very low power
mode that draws typically less than 10 mA from the input
source.
2401 Stanwell Drive • Concord, California 94520 • Ph: 925/687-4411 or 800/542-3355 • Fax: 925/687-3333 • www.calex.com • Email: sales@calex.com
3
3/2001
40 Watt XT Dual Series DC/DC Converters
Applying The Input
Figure 1 shows the recommended input connections for the
XT Dual DC/DC converter. A fuse is recommended to protect
the input circuit and should not be omitted. The fuse serves to
prevent unlimited current from flowing in the case of a
catastrophic system failure.
No external capacitance on the input is required for normal
operation, in fact it can degrade the converters performance.
Normal RF bypass capacitors in the 1000 pF to 0.01µF range
may be used without harm.
Remote ON/OFF Pin Operation
The remote ON/OFF pin may be left floating if this function is
not used. The equivalent input circuit for the ON/OFF pin is
shown in figure 3. The best way to drive this pin is with an open
collector/drain or relay contact. See our application note titled
“Understanding the remote ON/OFF function” for more
information about using the remote ON/OFF pin.
When the ON/OFF pin is pulled low with respect to the -
Input, the converter is placed in a low power drain state. The
ON/OFF pin turns the converter off while keeping the input
bulk capacitor fully charged, this prevents the large inrush
current spike that occurs when the +input pin is opened and
closed.
Figure 1.
Standard connections for the XT Dual. The ON/OFF and TRIM pins
may be left floating if they are not used. The input protection fuse
should not be omitted. If desired, external transient protection
diodes can be used. See the text below for suggestions regarding
input and output capacitance. The load may also be operated in
“Single ended” mode as shown.
Figure 3.
The simplified schematic of the XT Dual series ON/OFF pin. The
input impedance is approximately 6 k ohms. By leaving this pin
floating the converter will be in the ON state. When the pin is pulled
below 1.0 volts (with respect to the -Input pin) the converter is placed
in the power down or OFF state. See our application note on the
remote ON/OFF function for more information.
Ultra Low Noise Input Circuit
The circuit shown in figure 2 can be used to reduce the input
noise to below 20 mA p-p over a 20 MHz bandwidth. It is
important to size inductor L1 appropriately for the maximum
expected load current and input voltage. Capacitor C1 should
be the moderate ESR type specified. The use of a very low
ESR capacitor should be avoided as this will make a high-Q
filter when we really want a low-Q, controlled cutoff filter.
Applying The Output
Figure 1 shows typical output connections for the XT Dual. In
most applications no external output capacitance will be
necessary. Only your normal 1 to 10 µF and 0.001 to 0.1 µF
bypass capacitors sprinkled around your circuit as needed
locally are required. Do not add extra output capacitance and
cost to your circuit “Just Because”.
If you feel you must add external output capacitance, do
not use the lowest ESR, biggest value capacitor that you can
find! This can only lead to reduced system performance or
oscillation. See our application note “Understanding Output
Impedance For Optimum Decoupling” for more information or
use the ultra low noise output circuit below.
Output Trimming
The trim pin may be used to adjust the outputs from the
nominal factory setting. The trim may be used to adjust for
system wiring voltage drops. Figure 4 shows the proper
connections to use the trim pin. If output trimming is not
desired the trim pin may be safely left floating.
Trimming the output up reduces the output current
proportionally to keep the maximum power constant. Output
current is not increased over the listed maximum when
trimming the output voltage down.
A
Figure 2.
This circuit may be used to reduce the input reflected ripple to less
than 20 mA p-p. Capacitor C1 should be the moderate ESR type
shown to prevent input filter response peaking. Size the current
carrying capability of L1 for the maximum expected load and
minimum input operating voltage.
2401 Stanwell Drive • Concord, California 94520 • Ph: 925/687-4411 or 800/542-3355 • Fax: 925/687-3333 • www.calex.com • Email: sales@calex.com
4
3/2001
40 Watt XT Dual Series DC/DC Converters
Down trim can actually reduce the minimum input voltage in
some circuits. Full up trim may not be achievable at minimum
input voltage and full rated load.
Operation With Very Light Loads
The dynamic response of the XT Dual will degrade when the
unit is operated with less than about 25% of full rated power.
Grounding
The input and output sections are fully floating from each
other. They may be operated fully floating or with a common
ground. If the input and output sections are connected either
directly at the converter or at some remote location from the
converter it is suggested that a 3.3 to 10 µF, 0.5 to 5 Ohm ESR
capacitor bypass be used directly at the converter output pins.
This capacitor prevents any common mode switching currents
from showing up at the converters output as normal mode
output noise. See “Applying the Output” for more information.
FIGURE 4.
The output can be trimmed by either a trimpot or fixed resistors. If
fixed resistors are used their values may range from 0 to infinite
ohms. The trimpot should be typically 20 k ohms.
Non Standard Output Voltages
The XT Duals will typically trim much lower than the -10%
specified. This allows the XT’s to be trimmed lower than
specified for RF or other special applications.
The 5 volt XT’s can be typically trimmed over a range of 3.9
to 5.6 volts. The 12 volt XT’s can be typically trimmed over a
range of 6.4 to 13.3 volts. The 15 volt XT’s can be typically
trimmed over a range of 6.7 to 16.9 volts.
Single Ended 10, 24 or 30 V Outputs
The dual outputs may also be used in a single ended mode as
shown in figure 1 to get 10, 24 or 30 volts of output at the full
rated power levels. To use the single ended mode just
connect your load to the + and - Output pins and leave the
CMN pin floating. Trimming of the outputs may also be done
while using the single ended mode.
Ultra Low Noise Output Circuit
The circuit shown in figure 5 can be used to reduce the output
noise to below 20 mV p-p over a 20 MHz bandwidth. Size the
inductors appropriately for the maximum expected load current.
Another “Trick” that can be used when operating with a
common ground is to use a 10 to 100 µH choke between the
grounds. This gives you a solid low frequency ground
connection, but looks like a high impedance to the switching
current effects and prevents them from flowing in the
connection. This will have the effect of preventing the common
mode currents from showing up as normal mode components
in your input or output circuits.
Be sure that the inductor has a self resonant frequency of
greater than 200 kHz and that the Q of the inductor is quite low.
If necessary to keep the inductor Q under control, parallel it
with a 200 to 1 k ohm resistor.
Case Grounding
The copper case serves not only as a heat sink but also as a
EMI shield. The 0.25 inch thick case provides >30 dB of
absorption loss to both electric and magnetic fields at 220
kHz, while at the same time providing 20 to 40 % better heat
sinking over competitive thin steel, aluminum or plastic designs.
The case shield is tied to the output CMN pin. This
connection is shown on the block diagram. The case is
floating from the input sections. The input is coupled to the
outputs only by the low 500 pF of isolation capacitance. This
low I/O capacitance insures that any AC common mode noise
on the inputs is not coupled to your output circuits.
Compare this isolation to the more usual 1000 - 2000 pF
found on competitive designs and you will see that CALEX
provides the very best DC and AC isolation available. After all,
you are buying an isolated DC/DC to cut ground loops. Don’t
let the isolation capacitance add them back in.
A
Temperature Derating
The XT Dual series can operate up to 85°C case temperature
without derating. Case temperature may be roughly calculated
from ambient by knowing that the XT Duals case temperature
rise is approximately 4.4°C per package watt dissipated.
For example: If an XT converter is outputting 35 Watts, at
what ambient could it expect to run with no moving air and no
extra heatsinking?
Figure 5.
For very low noise applications this circuit will reduce the output
noise to less than 20 mV p-p over a 0-20 MHz bandwidth. Be sure
to size the inductor appropriately for the maximum expected load
current.
2401 Stanwell Drive • Concord, California 94520 • Ph: 925/687-4411 or 800/542-3355 • Fax: 925/687-3333 • www.calex.com • Email: sales@calex.com
5
3/2001
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