‘Hi Pot Test’, ‘Flash Tested’, ‘Withstand Voltage’, ‘Proof Voltage’, ‘Dielectric Withstand Voltage’ & ‘Isolation Test Voltage’ are all terms that relate to the same thing, a test voltage,
applied for a specified time, across a component designed to provide electrical isolation, to verify the integrity of that isolation.
C&D Technologies NDTS series of DC/DC converters are all 00% production tested at their stated isolation voltage. This is kVDC for second.
A question commonly asked is, “What is the continuous voltage that can be applied across the part in normal operation?”
For a part holding no specific agency approvals, such as the NDTS series, both input and output should normally be maintained within SELV limits i.e. less than 42.4V peak, or
60VDC. The isolation test voltage represents a measure of immunity to transient voltages and the part should never be used as an element of a safety isolation system. The part
could be expected to function correctly with several hundred volts offset applied continuously across the isolation barrier; but then the circuitry on both sides of the barrier must
be regarded as operating at an unsafe voltage and further isolation/insulation systems must form a barrier between these circuits and any user-accessible circuitry according to
safety standard requirements.
REPEATED HIGH-VOLTAGE ISOLATION TESTING
It is well known that repeated high-voltage isolation testing of a barrier component can actually degrade isolation capability, to a lesser or greater degree depending on materials,
construction and environment. The NDTS series has an EI ferrite core, with no additional insulation between primary and secondary windings of enameled wire. While parts can be
expected to withstand several times the stated test voltage, the isolation capability does depend on the wire insulation. Any material, including this enamel (typically polyurethane)
is susceptible to eventual chemical degradation when subject to very high applied voltages thus implying that the number of tests should be strictly limited. We therefore strongly
advise against repeated high voltage isolation testing, but if it is absolutely required, that the voltage be reduced by 20% from specified test voltage.
This consideration equally applies to agency recognized parts rated for better than functional isolation where the wire enamel insulation is always supplemented by a further
insulation system of physical spacing or barriers.
RoHS COMPLIANCE INFORMATION
This series is compatible with RoHS soldering systems with a peak wave solder
temperature of 300ºC for 0 seconds. The pin termination finish on this product series
is Tin. The series is backward compatible with Sn/Pb soldering systems.
For further information, please visit www.cd4power.com/rohs
www.cd4power.com
Technical enquiries
email: mk@cdtechno.com, tel:
+44 (0)908 65232
KDC_NDTSC.D01
Page 2 of 6
NDTS SERIES
Isolated 3W Single Output DC/DC Converters
APPLICATION NOTES
Recommended Input & Output Capacitors
Although these converters will work without external capacitors, they are necessary in order to guarantee the full parametric performance over the full line and load range. All
parts have been tested and characterized using the following values and test circuit.
Input Voltage
5V, 2V
24V, 48V
C
IN
00µF, 25V (0.25Ω at 00kHz)
0µF, 00V (.5Ω at 00kHz)
Output Voltage
3.3V, 5V
2V, 5V
C
OUT
220µF, 6V (0.2Ω at 00kHz)
00µF, 25V (0.25Ω at 00kHz)
Test circuit
+ V
OUT
Supply + V
IN
+ V
IN
C
IN
Supply - V
IN
- V
IN
NDTS
- V
OUT
C
OUT
Reflected Ripple Current Measurement
2
µ
H
Supply + V
IN
Current
Probe
+ V
IN
+ V
OUT
C
C
IN
NDTS
- V
OUT
C
OUT
Load
Supply - V
IN
C
= 220µF, ESR < 0.Ω at 00kHz
- V
IN
www.cd4power.com
Technical enquiries
email: mk@cdtechno.com, tel:
+44 (0)908 65232
KDC_NDTSC.D01
Page 3 of 6
NDTS SERIES
Isolated 3W Single Output DC/DC Converters
APPLICATION NOTES (continued)
Minimum Load
The minimum load for correct operation is 25% of the full rated load across the specified input voltage range. Lower loads may cause a significant increase in output ripple and
may cause the output voltage to exceed its specification transiently during power-down when the input voltage also falls below its rated minimum.
The following graphs show the typical required minimum load required for stable operation in mA verses input voltage. Some variants are not included as they do not typically
require a minimum load for stable operation: NDTD22C, and NDTD25C.
The NDTS series will operate from a wider input range than specified in the input characteristics datasheet table with output power derating. Please contact C&D Technologies for
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