Datasheet

NDH Series
Isolated 3W Dual Output DC/DC Converters
KDC_NDH.C02 Page 3 of 4
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RoHS COMPLIANCE INFORMATION
This series is compatible with RoHS soldering systems with a peak wave solder temperature of 300ºC
for 10 seconds. The pin termination finish on this product series is Tin Plate, Hot Dipped over Matte
Tin with Nickel Preplate. The series is backward compatible with Sn/Pb soldering systems.
For further information, please visit www.murata-ps.com/rohs
APPLICATION NOTES
External capacitance
Although these converters will work without external capacitors, they are neces-
sary 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.
Value
C
IN COUT
10μF, 200V 47μF, 25V
Test circuit
Control Pin
The NDH converters have a shutdown feature which enables the user to put the converter into a low power state. The control pin connects directly to the base of an
internal transistor, and the switch off mechanism for the NDH works by forward biasing this NPN transistor. If the pin is left open (high impedance), the converter will be
ON (there is no allowed low state for this pin), but once a control voltage is applied with sufficient drive current, the converter will be switched OFF. A suitable application
circuit is shown below.
D
1
(eg 1N4001) is required to provide high impedence when the signal
is low. From the NDH specification, the drive current to operate this
function is recommended to be 6mA, and hence the value of R
1
can be
derived as follows:
R
1
=
Assuming V
C
=5V, V
D
=0.7V and V
Q
=1V:
R
1
= = 550Ω
Cross Regulation
Load regulation is at its best when the positive and negative loads are balanced. When the loads are asymmetric, the negative output is not as tightly regulated as the
positive output. To meet ripple specification a total minimum load of 25% full load is required, however, the NDH can be used with much lighter loading at the expense
of increased ripple. A small load is required on the negative output of 150mW to ensure the maximum negative output voltage is not exceeded.
Cross regulation is defined as change in the negative output voltage as a percentage of nominal as the positive output load is changed from 12.5% to 50% with the
negative load is fixed at 50% of full load.
NDH
V
IN
V
C
OV
-V
IN
CTRL
R
1
D
1
Q
1
R
2
V
C
- V
D
- V
Q
I
C
5 - 0.7 - 1.0
6 x 10
-3
NDH
+VIN
+VOUT
-VOUT
OV
C
OUT
COUT
CIN
-VIN