NCS1 Series

Isolated 1W 4:1 Input Single Output DC/DC Converters

KDC_NCS1.A02 Page 2 of 8

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TEMPERATURE CHARACTERISTICS

Parameter

Conditions

Min.

Typ.

Max.

Units

Operation

-40

105

°C

Storage

-50

125

Case temperature above ambient

15

22

ABSOLUTE MAXIMUM RATINGS

Short-circuit protection (for SELV input voltages)

Continuous

Control pin input voltage

18V Max

Lead temperature 1.0mm from case for 10 seconds (to JEDEC JESD22-B106 ISS C)

260°C

Input voltage, NCS1 12V input types

25V

Input voltage, NCS1 24V input types

40V

APPLICATION NOTES

Start-up times

Part No.

Start-up times

ms

NCS1S1203SC

6

NCS1S1205SC

9

NCS1S1212SC

20

NCS1S2403SC

12

NCS1S2405SC

7

NCS1S2412SC

12

Control Pin

The NCS1 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 NCS1 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. 1N4003) is required to provide high impedence when the signal is low.

From the NCS1 specification, the drive current to operate this function is recom-

mended to be 3mA, 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

=

= 1100Ω

NCS1

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

Typical start up times for this series, with a typical input voltage rise time of 2.2μs and output capacitance of 10μF, are shown in the table below. The product series will

start into a capacitance of 47μF with an increased start time, however the maximum recommended output capacitance is 10μF.