QLS30 DC-DC Series Data Sheet
30A Quarter-Brick Converter
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
Typical Application
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.
Figure 7 shows the recommended connections for the
QLS30 Series converter.
QLS30ZX
Fuse
+Vo
+Vi
Negative Trim (No suffix)
+Sense
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.
C1
C2 C3
Trim
On/Off
-Vi
-Sense
-Vo
The negative trim schematic is shown in Figure 8.
Figure 7. Typical Application of QLS30 Series
The QLS30 Series converters do not require any external
components for proper operation.
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
33μF electrolytic capacitor with the ESR<0.7Ω is
recommended for the QLS30 Series.
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 using a 10μF
tantalum and a 1μF ceramic capacitors connected directly
across the output pins of the converter. Note that the
capacitors do not substitute the filtering required by the
load.
Figure 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.
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.
A− B×ΔV
kΩ
(1)
RTRIM
=
,
ΔV
where A and B are constants from the table below, and ΔV
is the absolute value of the desired change in the output
voltage in Volts.
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.
Model
Trim Up
Trim Down
A
B
1
A
B
QLS30ZB
QLS30ZA
QLS30ZY
0.57
0.283
0.5928
0.2711
0.065
1.4676
0.352
3.96
0.121
3.01
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.
0.5686
MCD10053 Rev. 1.0
Page 6 of 9
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