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QLS30ZA

30A Quarter-Brick DC/DC Converter

Power-One Inc. 

QLS30 Series – 30A Quarter-Brick DC/DC Converter

48V Input

1.8V, 1.5V, 1.2V Output

Data Sheet

Typical Application

Figure 7 below shows the recommended

connections for the QLS30 series converter.

Fuse

C1

QLS30ZX

+Vi

On/Off

+Vo

+Sense

Trim

C2 C3

-Sense

-Vi

-Vo

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).

Fig.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 to use 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.

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.

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

REV. 10/01

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.

Page 5 of 8

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