A
10 Watt WD Dual Series DC/DC Converters
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
eco# 030327-1, eco# 041007-1
Features
Isolated Dual Outputs
Universal 18 to 72 volt input range
Up to 10 Watts of PCB Mounted Power
Efficiencies to > 80%
Fully Isolated, Filtered Design
Low Noise Outputs
Very low I/O Capacitance, 375 pF typical
Water Washable Shielded Copper Case
Five Year Warranty
Description
The universal input of the WD Dual series spans 18 to 72 volts.
This makes these converters ideal for 24 and 48 volt battery,
process control and telecom applications.
Coupled with these features is a low output noise of
typically less than 80 mV peak to peak. The noise is also fully
specified for RMS value and if even these impressive noise
figures aren't enough, our applications section shows a
simple add on circuit that can reduce the output noise to less
than 10 mV p-p.
Full isolation is provided to help cut ground loops in
industrial systems, where unknown input power quality could
create havoc with sensitive, high precision analog circuitry.
No extra components or heatsinking are required for most
applications saving you design time and valuable PCB space.
10 Watt Dual WD Series Block Diagram
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What all this means to you is a tighter, more compact
overall system that has the capability of being universally
powered. Full application information is provided to make
integrating this supply in your system a snap.
Other input and output voltage combinations may be
factory ordered, contact CALEX applications engineering at
1-800-542-3355 for more information.
A
10 Watt WD Dual Series DC/DC Converters
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
eco# 030327-1, eco# 041007-1
NOTES
*
All parameters measured at Tc = 25C, 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.
(1)
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 10F tantalum and 0.01F
ceramic capacitor located 1 inch away from the converter. Input
ripple is measured into a 10H source impedance.
(2)
See our application note for picking the correct fuse size.
(3)
The converter may be safely operated at any load from zero to
the full rating. Dynamic response of the converter may degrade
if the converter is operated with less than 25% output load.
(4)
Load regulation is defined for loading/unloading both outputs
simultaneously. Load range is 25 to 100%.
(5)
Cross regulation is defined for loading/unloading one output
while the other output is kept at full load. Load range is
25 to 100%.
(6)
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)
Case is tied to the CMN output pin.
(8)
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.
(11) Water Washability - Calex DC/DC converters are designed to
withstand most solder/wash processes. Careful attention should
be used when assessing the applicability in your specific
manufacturing process. Converters are not hermetically sealed.
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A
10 Watt WD Dual Series DC/DC Converters
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
eco# 030327-1, eco# 041007-1
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Mechanical tolerances unless otherwise noted:
X.XX dimensions: 0.020 inches
X.XXX dimensions: 0.005 inches
Pin location shown is for the mating PCB
BOTTOM VIEW
SIDE VIEW
Applying The Input
Figure 1 shows the recommended input connections for the
WD 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.
Figure 1.
If the source impedance driving the WD Converter is more than
about 0.3 ohms at 120 kHz the optional capacitor C1 may be
required (See text for more information). Optional transient protec-
tor diodes may be used if desired for added input and output
protection. The output can be used as a 10, 24 or 30 V single output
as shown.
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 reduction circuits needed, no
heatsinking problems, just "plug and play".
The WD 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.
General Information
The universal 18 to 72 volt input allows you to specify your
system for operation from any 24 or 48 volt nominal input.
Five sided shielding is standard along with specified
operation over the full industrial temperature range of -40 to
+85C case temperature.
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A
10 Watt WD Dual Series DC/DC Converters
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
eco# 030327-1, eco# 041007-1
When using the WD Dual be sure that the impedance at the
input to the converter is less than 0.3 ohms from DC to about
120 kHz, this is usually not a problem in battery powered
systems when the converter is connected directly to the
battery. If the converter is located more than about 1 inch from
the input source an added capacitor may be required directly
at the input pins for proper operation.
The maximum permissible source impedance is a function
of output power and line voltage. The impedance can be
higher when operating at less than full power. The minimum
impedance is required when operating with a 18 volt input at
full load. In general you should keep the voltage measured
across the input pins less than 0.5 volts peak to peak (not
including the high frequency spikes) for maximum converter
performance.
There is no lower limit on the allowed source impedance,
it can be any physically realizable value, even approaching 0.
If the source impedance is too large in your system you
should choose an external input capacitor as detailed below.
Picking An External Input Capacitor
If an input capacitor is needed at the input to the converter it
must be sized correctly for proper converter operation. The
curve "RMS Input Current Vs Line Input" shows the RMS
ripple current that the input capacitor must withstand with
varying loading conditions and input voltages.
Several system tradeoff's must be made for each particular
system application to correctly size the input capacitor.
The probable result of undersizing the capacitor is increased
self heating, shortening it's life. Oversizing the capacitor can
have a negative effect on your products cost and size,
although this kind of overdesign does not result in shorter life
of any components.
There is no one optimum value for the input capacitor. The
size and capacity depend on the following factors:
1) Expected ambient temperature and your temperature
derating guidelines.
2) Your ripple current derating guidelines.
3) The maximum anticipated load on the converter.
4) The input operating voltage, both nominal and excursions.
5) The statistical probability that your system will spend a
significant time at any worst case extreme.
Factors 1 and 2 depend on your system design guidelines.
These can range from 50 to 100% of the manufacturers listed
maximum rating, although the usual derating factor applied is
about 70%. 70% derating means if the manufacturer rated the
capacitor at 1 A RMS you would not use it over 0.7 A RMS in
your circuit.
Factors 3 and 4 realistically determine the worst case ripple
current rating required for the capacitor along with the RMS
ripple current curve.
Factor 5 is not easy to quantify. At CALEX we can make no
assumptions about a customers system so we leave to you
the decision of how you define how big is big enough.
Suitable capacitors for use at the input of the converter are
given at the end of this section.
Very Low Noise Input Circuit
Figure 2 shows a very low noise input circuit that may be used
with the converters. This circuit will reduce the input reflected
ripple current to less than 10 mA peak-peak (Vin = 48 V, 10
kHz to 1 MHz bw). See the discussion above for the optimum
selection of C1.
Figure 2.
This circuit will reduce the input reflected ripple current to less than
10 mA peak to peak. See the discussion in the text for help on the
optimum selection of C1. L1 should be sized to handle the maximum
input current at your lowest operating voltage and maximum expected
output power.
Suggested Capacitor Sources
These capacitors may be used to lower your sources input
impedance at the input of the converter. These capacitors will
work for 100% load, worst case input voltage and ambient
temperature extremes. They however, may be oversized for
your exact usage, see "Picking An External Input Capacitor"
above for more information. You may also use several smaller
capacitors in parallel to achieve the same ripple current rating.
This may save space in some systems.
Suitable capacitors can be found from the following sources:
United Chemi-Con
SXE, RXC, RZ and RZA series
Suggested Part:
SXE100VB33RM10X15LL
33F, 100V, 105 C RATED
ESR=0.3 OHMS
Allowable Ripple at 85C = 0.8A
Nichicon
PR and PF series
Suggested Part:
UPR2A100MHH
100F, 100V, 105C RATED
ESR=0.18 OHMS
Allowable Ripple at 85C = 0.8A
Panasonic
TS-NH Series
Suggested Part:
ECES2AG331D
330F, 100V, 105C RATED
ESR=0.2 OHMS
Allowable Ripple at 85C = 1.1A
L1 = 20 H
C1 = See Text
C2 = 10 F/100 V, 0.25 - 1 ohm ESR
A
10 Watt WD Dual Series DC/DC Converters
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
eco# 030327-1, eco# 041007-1
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 1 to 10F, 0.5 to 5 ohm ESR
capacitor bypass be used directly at the converters output
pins. These capacitors prevent any common mode switching
currents from showing up at the converters output as normal
mode output noise. See "Applying the Output" for more
information on selecting output capacitors.
Also see the CALEX application note "Dealing With
Common Mode Noise" for more information on using common
grounds.
Case Grounding
The copper case serves not only as a heat sink but also as a
EMI shield. The 0.017 inch thick case provides >20 dB of
absorption loss to both electric and magnetic fields at 120
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 CMN output 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 375 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.
Temperature Derating
The WD Dual series can operate up to 85C case temperature
without derating. Case temperature may be roughly calculated
from ambient by knowing that the case temperature rise is
approximately 16C per package watt dissipated.
For example: If a WD Dual converter is delivering 8 Watts
with a 48 volt input, at what ambient could it expect to run with
no moving air and no extra heatsinking?
Efficiency of the converter is approximately 80% at 8 watts
of output power, this leads to an input power of about 10
Watts. The case temperature rise would be 10 - 8 Watts or 2
Watts x 16 = 32C. This number is subtracted from the
maximum case temperature of 85C to get: 53C.
This example calculation is for a WD Dual without any extra
heat sinking or appreciable air flow. Both of these factors can
greatly effect the maximum ambient temperature (see below).
Exact efficiency depends on input line and load conditions,
check the efficiency curves for exact information.
This is a rough approximation to the maximum ambient
temperature. Because of the difficulty of defining ambient
temperature and the possibility that the loads dissipation may
actually increase the local ambient temperature significantly,
these calculations should be verified by actual measurement
before committing to a production design.
Applying The Output
Figure 1 shows typical output connections for the WD Dual. In
most applications no external output capacitance will be
necessary. Only your normal 1 to 10F tantalum and 0.001 to
0.1F ceramic 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
and by all means use our low noise circuit provided.
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.
Ultra Low Noise Output Circuit
The circuit shown in figure 3 can be used to reduce the output
noise to below 10 mV p-p over a 20 MHz bandwidth. Size
inductor L1 appropriately for the maximum expected load
current. All of the ground connections must be as short as
possible back to the CMN pin. The filter should be placed as
close to the WD Dual as possible, even if your load is at some
distance from the converter.
Figure 3.
This circuit can reduce the output noise to below 10 mV p-p over a
20 MHz bandwidth. Size inductor L1 appropriately for the maximum
expected load current. The filter should be constructed as close as
possible to the converter and all of the ground connections must be
as short as possible back to the CMN pin.
Operation With Very Light Loads
Dynamic response and cross regulation of the WD Dual will
degrade when the unit is operated with less than about 25%
of full rated power. If this is a problem the most lightly loaded
output may be "Pre-Loaded" with a resistor to common as
needed. The exact amount of preloading required is dependent
on your system requirements, so some experimentation is
necessary to arrive at the optimum value.
L1 = 20 H
C1 = 22 F / 20 V, Tantalum
C2 = 0.01 F / 100 V, Ceramic
A
10 Watt WD Dual Series DC/DC Converters
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
6
eco# 030327-1, eco# 041007-1
Typical Performance (Tc=25C, Vin=Nom VDC, Rated Load).
15
25
35
45
55
65
75
LINE INPUT(VOLTS)
70
75
80
85
90
EFFICIENCY(%)
EFFICIENCY Vs. LINE INPUT VOLTAGE
100% FULL LOAD
50% FULL LOAD
0
10
20
30
40
50
60
70
80
90
100
LOAD (%)
70
75
80
85
90
EFFICIENCY (%)
EFFICIENCY Vs. LOAD
LINE = 18VDC
LINE = 48VDC
LINE = 72VDC
0
10
20
30
40
50
60
70
80
LINE INPUT (VOLTS)
0.0
0.2
0.4
0.6
0.8
1.0
INPUT CURRENT (AMPS)
INPUT CURRENT Vs. LINE INPUT VOLTAGE
100% LOAD
50% LOAD
15
25
35
45
55
65
75
LINE INPUT (VDC)
0.0
0.2
0.4
0.6
0.8
RMS INPUT CURRENT (AMPS)
RMS INPUT CURRENT Vs. LINE INPUT
100% LOAD
75% LOAD
50% LOAD
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