NTF Series
Isolated 1W Wide Input DC/DC Converters
APPLICATION NOTES
Recommended input & output capacitors
Value
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.
CIN
COUT
10μF, 200V
good low esr capacitor
22μF, 16V
good low esr capacitor
Test circuit, 5V, 12V and 15V output
+ VIN
+ VOUT
CIN
NTF
COUT
- VOUT
- VIN
ON/OFF Pin
This provides an OFF function, which puts the converter into a low power mode. When the pin is un-connected, the converter is on. The circuit used must be able to sink a peak
curent of 50mA to guarantee turning the converter off. The circuit should be an open collector arrangement, an example circuit is shown below. Voltages should not be applied
directly to the ON/OFF pin. The BC547 should be fitted close to the NTF ON/OFF pin to prevent the addition of excess wiring capacitance.
CTRL
47kꢀ
BC547
VCONTROL
NTF
100nF
- VIN
CONTROL PIN CIRCUIT INPUT VOLTAGE VCONTROL
Min.
0
Max.
0.2
30
Units
V
V
Module ON
Module OFF
1.6
Output voltage adjustment
The trim resistor equations are:
Where:
R
DOWN = (VDOWN - L) x G
G
L
K
V
NOM - VDOWN
NTFS0505MC
NTFS1205MC, NTFS2405MC
NTFSXX12MC
30100
100000
38300
49900
1.24
1.24
2.5
3.76
3.76
9.5
R
UP
=
G x L
UP - L - K
V
2.5
12.5
NTSFXX15MC
TRIM UP
TRIM DOWN
+VIN
+VOUT
+VIN
+VOUT
RDOWN
TRIM
NTF
NTF
TRIM
RUP
-VOUT
-VOUT
When the output voltage is trimmed up, output current must be derated so that the maximum output power is not exceeded.
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KDC_NTFC.A02 Page 6 of 8
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