Datasheet

NDL Series
Isolated 2W Wide Input Single Output DC/DC Converters
KDC_NDL.F05 Page 3 of 4
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APPLICATION NOTES
External capacitance
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.
Value
Input Voltage (V) CIN COUT
5 & 12 100µF, 25V 100µF, 25V
24 & 48 10µF, 200V 100µF, 25V
Test circuit
Control Pin
The NDL 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 NDL 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
(e.g. 1N4001) is required to provide high impedence when the signal is
low. From the NDL specification, the drive current to operate this function
is recommended to be 10mA, 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
= = 330
Pin 8 (CS)
This pin provides a connection point to the main reservoir capacitor. Additional capacitance can be added from this pin to pin 7. Any lower ESR capacitor will remove ripple
and noise to some degree. The benefit of this access point over simple additional output capacitance is that it precedes the output filter inductor. Maximum values of external
capacitance will be dependent on the output voltage, the loading of the converter and the desired ripple figure. Values can be up to 100µF.
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.
NDL
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
10 x 10
-3
NDL
COUT
CIN
- V
IN
+ V
IN
+ V
OUT
Supply + V
IN
Supply - V
IN
- V
OUT
RoHS COMPLIANT 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
NDL05 POWER DERATING CURVE
4.5
Isolation voltage (V)
Output Power (W)
0.5
0
56789
1.0
1.5
1.75
2.0
2.5