
MCD10089 Rev. 1.1, 8-Oct-08
Page 5 of 9
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QKS48T21120 DC-DC Bus Converter Data Sheet
Quarter-Brick with 48VDC Input; 12VDC @ 21A Output
Efficiency Curve
Figure 1. QKS48T21120 Efficiency vs. Output Load
Typical Application
Figure 2 shows the recommended connections for
the QKS48T21120 converter.
+Vo
-Vo
-Vi
+Vi
On/Off
Fuse
C1
C3
Figure 2. Typical Application of QKS48T21120
The QKS48T21120 converter does not require any
external components for proper operation. However,
a 100 μF low ESR input capacitor and a 330 μF
output capacitor are recommended for optimal
performance
Refer to the “Inrush Current Control Application
Note” on www.power-one.com for suggestions on
how to limit the magnitude of the inrush current.
Shutdown Feature Description
The ON/OFF pin in the QKS48T21120 converter
functions as a normal soft shutdown. It is referenced
to the –Vin pin (see Figure 2). With the positive
logic, when the ON/OFF pin is pulled low, the output
is turned off and the unit goes into a very low input
power mode.
With negative logic, when the ON/OFF pin is pulled
low, the unit is turned on.
An open collector switch is recommended to control
the voltage between the ON/OFF pin and the -Vin
pin of the converter. The ON/OFF pin is pulled up
internally, so no external voltage source is required.
The user should avoid connecting a resistor between
the ON/OFF pin and the +Vin pin.
When the ON/OFF pin is used to achieve remote
control, the user must take care to insure that the pin
reference for the control is really the -Vin pin. The
control signal must not be referenced ahead of EMI
filtering, or remotely from the unit. Optically coupling
the information and locating the optical coupler
directly at the module will solve any of these
problems.
Note:
If the ON/OFF pin is not used, it can be left floating (positive logic),
or connected to the -Vin pin (negative logic).