QLS30 Series – 30A Quarter-Brick DC/DC Converter
48V Input
1.8V, 1.5V, 1.2V Output
Data Sheet
REV. 10/01 Page
5 of 8
Typical Application
Figure 7 below shows the recommended
connections for the QLS30 series converter.
+Vo
+Sense
Trim
-Sense
-Vo
-Vi
+Vi
On/Off
Fuse
C1
C2
C3
QLS30ZX
Fig.7 Typical application of QLS30 series
The QLS30 series converters do not require any
external components
However, if the distribution of the input voltage to
the converter contains significant inductance, the
capacitor C1 may be required to enhance
performance of the converter. A minimum of a
33
μ
F electrolytic capacitor with the ESR<0.7
is
recommended for the QLS30 series.
for
proper
operation.
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.
For output decoupling we recommend to use a
10
μ
F tantalum and a 1
μ
F ceramic capacitors
connected directly across the output pins of the
converter. Note that the capacitors do not
substitute the filtering required by the load.
Shutdown Feature Description
The ON/OFF pin in the QLS30 series converters
functions as a normal soft shutdown. It is
referenced to the –Vin pin (see Figure 7). With
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).
Output Voltage Trim
The trim feature allows the user to adjust the
output voltage from the nominal. This can be used
to accommodate a different requirement or to do
production margin testing. There are two
variances available in the QLS30 series.
Negative Trim (No suffix)
The QLS30 negative trim units trim up with a
resistor from the TRIM pin to the –Sense pin and
trim down with a resistor from the TRIM pin to the
+Sense pin, as shown in Fig.8.
The negative trim schematic is shown in Figure 8.
Fig.8 QLS30 series negative trim schematic
The general equation (1) for changing the output
voltage on the negative trim modules is invariant,
but the constants in the equation change due to
different internal values.