20 Watt NT Single Series DC/DC Converters
Features
Fully Self Contained, No External Parts
Required for Operation
Low and Specified Input/Output Capacitance
Efficiencies to 85%
Overcurrent Protected and Thermal Shutdown
Circuitry for Long, Reliable Operation
Five-sided, Shielded, Low Thermal
Gradient Copper Case
5 Year Warranty
Water Washable Case Design
Description
These 20 Watt NT converters are ideal for battery operated
industrial, medical control and remote data collection systems.
They have achieved an exceptionally low input/output
capacitance (290 pF) that is half that of comparable models.
This low capacitance contributes to their exceptional input/
output isolation.
Complete overload protection with independent pulse-by-
pulse current limiting and an overtemperature shutdown
circuit ensure zero-failure rate operation. Each converter is
encased in a five-sided, shielded and sealed water washable
case.
Model
12S3.4000NT
12S5.4000NT
12S12.1700NT
12S15.1400NT
24S3.4000NT
24S5.4000NT
24S12.1700NT
24S15.1400NT
48S3.4000NT
48S5.4000NT
48S12.1700NT
48S15.1400NT
Selection Chart
Input Range
VDC
Min
Max
9
18
9
18
9
18
9
18
18
36
18
36
18
36
18
36
36
72
36
72
36
72
36
72
Output
VDC
3.33
5
12
15
3.33
5
12
15
3.33
5
12
15
Output
mA
4000
4000
1700
1400
4000
4000
1700
1400
4000
4000
1700
1400
20 Watt NT Single 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
eco# 041007-1
20 Watt NT Single Series DC/DC Converters
Input Parameters*
Model
Voltage Range
Reflected Ripple (2)
Input Current Full Load
No Load
Efficiency
Switching Frequency
Maximum Input
Overvoltage,
100ms Maximum
Turn-on Time,
1% Output Error
Recommended Fuse
Model
Voltage Range
Reflected Ripple (2)
Input Current Full Load
No Load
Efficiency
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
45
10
(3)
1.00
10
85
MIN
MAX
TYP
TYP
TYP
TYP
TYP
TYP
MAX
TYP
24
10
(3)
24S12.1700NT 24S15.1400NT
18
36
35
10
1.02
10
86
0.35
8
80
220
85
0.50
8
83
48S3.4000NT
48S5.4000NT
48S12.1700NT 48S15.1400NT
36
72
20
6
0.51
8
84
0.51
8
85
1.46
16
76
2.12
16
79
12S3.4000NT
12S5.4000NT
12S12.1700NT 12S15.1400NT
9
18
40
15
2.15
16
79
220
45
2.21
16
79
0.70
10
80
24S3.4000NT
18
36
35
10
1.01
10
83
24S5.4000NT
Units
VDC
mA P-P
mA RMS
A
mA
%
kHz
VDC
ms
AMPS
Units
VDC
mA P-P
mA RMS
A
mA
%
kHz
VDC
ms
AMPS
Output Parameters*
Model
Output Voltage
Output Voltage Accuracy
Rated Load Range
Load Regulation
25% Max-Max Load
Line Regulation
Vin = Min-Max VDC
Short Term Stability (4)
Long Term Stability
Transient Response (5)
Dynamic Response (6)
Input Ripple Rejection (7)
Noise, 0-20MHz bw (2)
RMS Noise, 0.01-1MHz
Temperature Coefficient
Short Circuit Protection to
Common for all Outputs
NOTES
MIN
TYP
MAX
MIN
MAX
TYP
MAX
TYP
MAX
TYP
TYP
TYP
TYP
TYP
TYP
TYP
TYP
MAX
12S3.4000NT
24S3.4000NT
48S3.4000NT
3.33
3.30
3.33
3.36
0.0
4.0
0.3
0.6
0.5
1.0
12S5.4000NT
24S5.4000NT
48S5.4000NT
5
4.95
5.00
5.05
0.0
4.0
0.2
0.4
12S12.1700NT
24S12.1700NT
48S12.1700NT
12
11.90
12.00
12.10
0.0
1.7
0.1
0.2
0.01
0.1
< 0.05
< 0.2
300
300
> 40
50
8
50
150
A
12S15.1400NT
24S15.1400NT
48S15.1400NT
15
14.90
15.00
15.10
0.0
1.4
0.1
0.2
Units
VDC
VDC
A
%
%
%/24Hrs
%/kHrs
µs
mV peak
dB
mV P-P
mV RMS
ppm/°C
50
100
50
10
300
60
14
350
50
8
Continuous, Current Limit and Thermal Protection
*
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.
(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 0.01µF ceramic in parallel with a 1µF/35V Tantalum capacitor
located 1" away from the converter to simulate
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# 041007-1
20 Watt NT Single 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
12S Models
24S and 48S Models
Isolation (8)
Isolation Voltage
Input to Output 12S, 24S
Input to Output 48S
10µA Leakage
Input to Output
Capacitance
Output Trim Function
Trim Range
Input Resistance
Open Circuit Voltage
Environmental
Case Operating Range
No Derating
Case Functional Range (9)
Storage Range
Thermal Shutdown
Case Temperature
Thermal Impedance (10)
General
Unit Weight
Chassis Mounting Kit
MIN
MIN
TYP
700
1544
290
Units
MIN
MAX
TYP
TYP
>1.6
<0.7
2.5
20
VDC
VDC
VDC
kohms
TYP
TYP
13
14
mA
mA
BOTTOM VIEW
VDC
SIDE VIEW
Mechanical tolerances unless otherwise noted:
pF
X.XX dimensions: ±0.020 inches
X.XXX dimensions: ±0.005 inches
MIN
MIN
TYP
MIN
MAX
MIN
MAX
MIN
MAX
TYP
TYP
TYP
±5
10
2.5
-40
90
-55
100
-55
105
105
9.5
2.3
MS8
%
kohms
VDC
°C
°C
°C
°C
°C/Watt
oz
Pin
1
2
3
4
5
6
Function
ON/OFF
-INPUT
+INPUT
+OUTPUT
CMN
TRIM
NOTES (cont.)
your PCB’s standard decoupling. Input reflected ripple is measured
into a 10µH source impedance.
(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 µSec)
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 input ripple rejection is specified for DC to 120 Hz ripple with
a modulation amplitude of 1% of Vin.
(8) The Case is tied to the -IN pin.
(9) 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.
(10) The case thermal impedance is specified as the case
temperature rise over ambient per package watt dissipated.
(11) Specifications subject to change without notice.
(12) 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.
A
Applications Information
General Information
The 20 Watt NT Single series is also 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 3 mA from the input source.
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 20 Watt
single will provide zero failure rate operation.
A fully five-sided shielded, sealed, water washable case is
standard along with specified operation over the full industrial
temperature range of -40 to +90°C.
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# 041007-1
20 Watt NT Single Series DC/DC Converters
General Operation
Figure 1 shows the recommended connections for the 20 Watt
NT Single DC/DC converter. A fuse is recommended to
protect the input circuit and should not be omitted.
For applications that require remote sensing, the circuit
shown in Figure 3 may be used. This circuit can adjust for up
to 0.25 Volts drop in a 5 Volt output. This is equivalent to 0.06
ohms at 4 Amps.
D1, D2 - Overvoltage clamp is optional, see text
Figure 1.
Standard connections for the 20 Watt NT Single: The ON/OFF and
TRIM pins can be left floating if they are not used. The input fuse
should not be omitted. The overvoltage diodes may be added to the
circuit directly at the converter to provide transient protection to your
circuit.
R1 = 470 OHM, 1/4W, 5%
R2 = 1.0K, 1/4W, 5%
R3 = 2.4K, 1/4W, 5%
R4, R5 = 4.99K, 1/4W, 5%
C1 = 0.01µF, 100V, CER
D1 = 1N4448
Q1 = 2N3906
IC1 = TL431CLP
The ON/OFF and +5 TRIM pins may be left floating if they
are not used. No external capacitance on either the input or
outputs is required for normal operation, in fact, it can degrade
the converter’s performance. See our application note
“Understanding DC/DC Converters Output Impedance” and
the low noise circuits later in this data sheet for more information.
The usual 0.1 to 0.001 µF bypasses may be used around your
PCB as required without harm.
Extremely low ESR capacitors (< 0.5 ohms) should not be
used at the input as this will cause peaking of the input filter’s
transfer function and actually degrade the filter’s performance.
Applying the Output
The output is simply connected to your application circuit and
away you go. If extra low output noise is required in your
application the circuit shown in Figure 2 may be used to
reduce the output noise to below 10 mV P-P.
Figure 3.
This remote sensing circuit can be used to automatically adjust for
voltage drops in your system’s wiring.
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 10 kohms nominal for 3.3 and 5 Volt
units and 20 kohms for 12 and 15 Volt outputs.
A
Non Standard Output Voltages
L1 = 2µH
C1, C3 = 0.01µF, CERAMIC
C2 = 10µF/35V, TANTALUM
The trim may be used to adjust a +5 output unit up to 5.2 Volts
for ECL applications.
+12 Volt units will trim around a range of approximately
+9.6 to +12.6 Volts. +15 Volt units will trim around a range of
approximately +12 to +15.75 Volts.
Maximum power from the module is limited to the specified
non-trimmed maximum (Typical Output Voltage x Maximum
Rated Load = Maximum Power). Trimming the output up
reduces the output current proportionally to keep the maximum
power constant. Output current is not increased over the
Rated Maximum when trimming the output voltage down.
See our application note on remote sense and trim functions
for more information.
Figure 2.
For very low noise applications the circuits shown above can be
used. The input current ripple will be reduced approximately 30 dB
of the original value while the output noise will be reduced to typically
below 10 mV P-P.
The trim pin may be used to adjust the outputs by up to +5
% from the nominal factory setting to account 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.
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# 041007-1
20 Watt NT Single Series DC/DC Converters
Grounding
The input and output sections are fully floating from each
other. They may be operated 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 10µF, 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 converter’s output as normal mode
output noise. 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.
Case Grounding
The case serves not only as a heat sink but also as an EMI
shield. The 0.02 inch thick copper provides >25 dB of absorption
loss to both electromagnetic and electric fields at 220 kHz,
while at the same time providing about 30% better heat
sinking than competitive 0.01 inch thick steel cases.
The case shield is tied to the -input pin. This connection is
shown on the block diagram. The case is floating from the
input, coupled only by the 290 pF of isolation capacitance.
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 5. 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. When
the ON/OFF pin is released the converter fully powers up in
typically 10 milliseconds. 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.
Temperature Derating
The NT Single Series can operate up to 90°C case temperature
without derating. Case temperature may be roughly calculated
from ambient by knowing that the NT Singles case temperature
rise is approximately 9.5°C per package watt dissipated.
For example: If a 24 Volt input converter was delivering 15
Watts at 24 Volts input, at what ambient could it expect to run
with no moving air and no extra heat sinking?
Efficiency is approximately 86%. This leads to an input power
of about 17.4 Watts. The case temperature rise would be 2.4
Watts x 9.5 = 22.8°C. This number is subtracted from the
maximum case temperature of 90°C to get 67°C.
This is a rough approximation to the maximum ambient
temperature. Because of the difficulty of defining ambient
temperature and the possibility that the load’s dissipation may
actually increase the local ambient temperature significantly
or that convection cooling is suppressed by physical placement
of the module, these calculations should be verified by actual
measurement of operating temperature and your circuit’s
exact efficiency (efficiency depends on both line input and
load value) before committing to a production design.
A
Figure 5.
The simplified schematic of the NT Single Series ON/OFF pin. The
input impedance is approximately 20 kohms. The maximum open
circuit voltage is approximately 2.5 Volts. By leaving this pin floating
the converter will be in the ON state. When the pin is pulled below
0.7 Volts the converter is placed in the power down or OFF state.
See our application note on the remote ON/OFF function for more
information.
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# 041007-1
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