A
6 Watt LV Single 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
3/2001, eco# 041007-1
Features
Universal 3.5 to 16 Volt Input Range
Up to 6 Watts of PCB Mounted Power
Efficiencies to 77%
Fully Isolated, Filtered Design
-40 to 85C Operation
Very Low I/O Capacitance, 300 pF Typical
Small Water Washable Nonconductive Case
5 Year Warranty
Description
The universal input of the LV single series spans 3.5 to 16
volts. This makes these converters ideal for 4.8 to 12 volt
battery and the more traditional 5 volt logic powered systems.
Coupled with this is the nonconductive case which makes
for safe installation on tight, multi-board systems. No extra
components or heatsinking are required for most applications
saving you design time and valuable PCB space.
Full isolation is provided to help cut ground loops in logic
powered systems that could create havoc with sensitive, high
precision analog circuitry.
What all this means to you is a tighter, more compact
overall system that has the capability of being universally
6 Watt LV Single Series Block Diagram
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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.
As with all CALEX converters the LV Single series is
covered by our 5 Year Warranty.
A
6 Watt LV Single 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
3/2001, 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)
Reduced output power available at 3.5V input. Full output power
is available above 4.6V input. See applications section for more
information.
(2)
Noise is measured per CALEX Application Notes. Measurement
bandwidth is 0-20 MHz for peak-peak measurements, 10 kHz to
1 MHz for RMS measurements. Output noise is measured with
a 0.01F ceramic in parallel with a 1F/35V Tantalum capacitor
located 1" away from the converter to simulate your PCB's
standard decoupling.
(3)
To determine the correct fuse size, see CALEX Application
Notes.
(4)
Short term stability is specified after a 30 minute warmup
at full load, constant line and recording the drift over a 24
hour period.
(5)
The transient response is specified as the time required to settle
from a 50 to 75 % step load change (rise time of step = 2 Sec)
to a 1% error band.
(6)
Dynamic response is the peak overshoot voltage during the
transient response time as defined in note 5 above.
(7)
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 will reduce expected operational life.
The data sheet specifications are not guaranteed over the
functional temperature range.
(8)
The case thermal impedance is specified as the case
temperature rise over ambient per package watt dissipated.
(9)
No minimum load required for operation . Dynamic regulation
may degrade when run with less than 5% load.
(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
6 Watt LV Single 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
3/2001, eco# 041007-1
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Mechanical tolerances unless otherwise noted:
X.XX dimensions: 0.020 inches
X.XXX dimensions: 0.005 inches
Applying the Input
Figure 1 shows the recommended input connections for the
LV Single 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 LV Converter is more than 0.15
ohms the optional capacitor C2 may be required (See text for more
information). Optional transient protector diode D1 may be used if
desired for added protection. The fuse serves as a catastrophic
failure protector and should not be omitted.
When using the LV Single be sure that the impedance at
the input to the converter is less than 0.15 ohms from DC to
about 200 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 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
Application 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 circuits needed, no heatsinking
problems, just "plug and play".
The LV Single 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 3.5 to 16 volt input allows you to specify your
system for operation from any 5 volt logic supply or a 4.8 to 12
volt nominal battery input.
Noise has also achieved new lows in this single 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 LV converters achieve noise levels of less
than 50 mV peak to peak (S12 and S15 models) and are fully
specified and tested to a wide bandwidth of 0-20 MHz.
A water washable, non-conductive case is standard along
with specified operation over the full industrial temperature
range of -40 to +85C case temperature.
BOTTOM VIEW
SIDE VIEW
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A
6 Watt LV Single 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
3/2001, eco# 041007-1
L1 = 10H
C1 = 10F / 25V, TANTALUM
C2 = SEE TEXT
Generally this is not a problem with battery powered
circuits and only appears when the LV Single is powered by
marginally sized 5 or 12 volt linear supplies that can't supply
the required startup current. See the "Input Current Vs. Line
Input" curve for the low voltage current requirements of the LV
Single.
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 5 mA RMS (Vin = 5 V, 10 kHz to 1
MHz bw). See the discussion above for the optimum selection
of C2.
Figure 2.
This circuit will reduce the input reflected ripple current to less than
5 mA RMS. See the discussion in the text for help on the optimum
selection of C2. 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 the 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.
United Chemi-Con LXF, SXE, RXC, RZ and RZA series
Suggested Part:
LXF25VB221M8X15LL
220F, 25V, 105C Rated
ESR = 0.13 ohms
Allowable Ripple at 85 C = 960 mA
Nichicon
PR and PF series
Suggested Part:
UPR1E102MRH
1000F, 25V, 105C Rated
ESR = 0.1 ohms
Allowable Ripple at 85C = 1.2 A
Panasonic
HFG and HFQ Series
Suggested Part:
ECEA1EFG102
1000F, 25V, 105C Rated
ESR = 0.05 ohms
Allowable Ripple at 105C = 1.28 A
required when operating with about a 6 volt input. The
impedance reduces as the input voltage is raised or lowered
or the power is reduced. In general you should keep the peak
to peak voltage measured across the input pins less than 0.25
volts peak to peak (not including the high frequency spikes)
for maximum converter performance and life.
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 tradeoffs 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%. For example 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.
Startup Current Demand
Because the LV Single appears as a constant power load to
your source and operation starts at about 3 volts, you should
be sure that your source can supply the required current at low
voltages when starting.
A
6 Watt LV Single 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
3/2001, eco# 041007-1
Applying the Output
Figure 3 shows typical output connections for the LV Single.
In most applications no external output capacitance will be
necessary. Only your normal 1 to 10 F tantalum and 0.001
to 0.1 F 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.
Figure 3.
The LV Single may be directly connected to your load without any
external components required for most applications. Transient
overvoltage diode D1 may be added for extra protection against
output faults or if the input has the possibility of being shorted to the
load. General Semiconductor or Motorola SA and 1.5KE series
devices provide excellent protection.
Output Power
The available output power of the LV Single is reduced when
operating below 4.6 volts. See the "Low Voltage Power" curve
for more information. In general, from 4.6 to 16 volts full power
is available from the LV Single. Below 4.6 volts input the
available output power is linearly derated from 100% at 4.6
volts to 50% at 3.5 volts. For example a 5S12.500LV is
capable of providing 3 watts of output power at 3.5 volts input.
Ultra Low Noise Output Circuit
The circuit shown in figure 4 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 LV Single as possible, even if your load is at some
distance from the converter.
Operation With Very Light Loads
The LV Single conserves power when operating at very light
loads by operating in a burst power mode. This may cause the
output noise to increase with a repetition rate of 10's of
milliseconds. If this causes a problem the LV Single may be
operated with a pre-load of about 5% of it's full rated power.
The exact value will depend on the external components in
your system.
Dynamic response of the LV Single will degrade when the
unit is operated with less than 25% of full rated power.
L1 = 10H
C1 = 100F / 25V, ALUMINUM
C2 = 10F / 25V, TANTALUM
Figure 4.
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. All of the ground connections must be as
short as possible back to the CMN pin.
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 10 F, 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 case is made from a non-conductive high temperature
plastic material. The case is floating from the input sections.
The input is coupled to the outputs only by the low 300 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.
Temperature Derating
The LV Single 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 19C per package watt dissipated.
For example: If a 12 volt output converter is delivering 4.5
watts with a 5 volt input, at what ambient could it expect to run
with no moving air and no extra heatsinking?
Efficiency of the converter is approximately 74% at 4.5
watts of output power, this leads to an input power of about 6
watts. The case temperature rise would be 6 - 4.5 watts or 1.5
watts
19 = 29C. This number is subtracted from the
maximum case temperature of 85C to get: 56C.
A
6 Watt LV Single 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
3/2001, eco# 041007-1
This example calculation is for an LV Single without any
extra heat sinking or appreciable air flow. Both of these factors
can greatly effect the maximum ambient temperature. 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.
Remember, it is the system designers responsibility to be
sure that the case temperature of the LV Single does not
exceed 85C for maximum reliability in operation.
0
10
20
30
40
50
60
70
80
90
100
LOAD (%)
60
65
70
75
80
EFFICIENCY (%)
EFFICIENCY Vs. LOAD
LINE = 5VDC
LINE = 16VDC
0
2
4
6
8
10
12
14
16
LINE INPUT (VOLTS)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
INPUT CURRENT (AMPS)
INPUT CURRENT Vs. LINE INPUT VOLTAGE
100% LOAD
50% LOAD
10
100
1000
10000
100000
1000000
FREQUENCY (Hz)
.01
.1
1
10
OUTPUT IMPEDANCE (OHMS)
OUTPUT IMPEDANCE Vs. FREQUENCY
5 VOLT OUTPUT
12/15 VOLT OUTPUT
4
6
8
10
12
14
16
LINE INPUT(VOLTS)
65
70
75
80
85
EFFICIENCY(%)
EFFICIENCY Vs. LINE INPUT VOLTAGE
100% FULL LOAD
50% FULL LOAD
3
5
7
9
11
13
15
17
LINE INPUT (VDC)
0.0
0.2
0.4
0.6
0.8
1.0
RMS INPUT CURRENT (AMPS)
RMS INPUT CURRENT Vs LINE INPUT
100% LOAD
75% LOAD
50% LOAD
Typical Performance (Tc=25C, Vin=Nom VDC, Rated Load).
3.50
3.75
4.00
4.25
4.50
4.75
5.00
LINE INPUT (VDC)
0
20
40
60
80
100
120
% AVAILABLE POWER
LOW VOLTAGE POWER AVAILABLE
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