
DS_NC12S60A_02072007
7
FEATURES DESCRIPTIONS
Remote On/Off
The remote ON/OFF input allows external circuitry to put
the NC converter into a sleep mode. Active-high remote
on/off is available as standard.
Active-high units of the NC series are turned on if the
remote ON/OFF pin is high (or floating). Pulling the pin low
will turn off the unit. To guarantee turn-on the enable
voltage must be above 2.4V and to turn off the enable
voltage must be pulled below 0.8V
The remote ON/OFF input can be driven in a variety of
ways as shown in Figures 26, 27, and 28. If the remote
ON/OFF signal originates on the primary side, the remote
ON/OFF input can be driven through a discrete device
(e.g. a bipolar signal transistor) or directly from a logic
gate output. The output of the logic gate may be an
open-collector (or open-drain) device. If the drive signal
originates from the opposite of an isolated side, the
remote ON/OFF input can be isolated and driven through
an opto-coupler.
Figure26:
Remote ON/OFF Input Drive Circuit for Non-Isolated
Bipolar
Figure 27
:
Remote ON/OFF Input Drive Circuit for Logic Driver
DESIGN CONSIDERATIONS
The NC60A is designed using three-phase synchronous
buck topology. Block diagram of the converter is shown in
Figure 25. The output can be trimmed in the range of 0.9V
to 5.0V by a resistor from trim pin to ground. The remote
sense is able to compensate for a drop from the output of
converter to point of load.
The converter can be turned on/off by remote control.
Positive OUTEN logic implies that the converter DC
output is enabled when this signal is driven high (greater
than 2.4V) or floating and
disabled when
low (below
0.8V). Negative OUTEN logic is an option.
The converter provides an open collector signal, Power
Good. The power good signal is pulled low when output is
not within ±10% of Vout or when Enable is off.
The converter can protect itself into hiccup mode against
over current and short circuit condition. Also, the
converter will shut down due to over voltage protection is
detected.
The converter has an over temperature protection which
can protect itself by shutting down for an over
temperature event. There is a thermal hysteresis of
typically 25
℃
Safety Considerations
It is recommended to add a fuse at input line. As to
current rating of the fuse, it depends on the output voltage
and current setting.
o
o
TRIM
Vo
GROUND
o
o
o
5V
VIN
GROUND
OUTEN
o
o
TRIM
Vo
GROUND
o
o
o
VIN
GROUND
OUTEN
Figure 25:
Block Diagram