QLS25 DC-DC Series Data Sheet
25A Quarter-Brick
Features
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Applications
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Distributed power architectures
Telecommunications equipment
LAN/WAN applications
Data processing applications
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Description
The QLS25 is a new series of cost-effective, high-density single output DC-DC converters providing onboard
conversion of standard telecom and datacom input voltages into isolated low voltage outputs in a through-hole
mounting package. High efficiencies and a patent-pending board design significantly improve thermal
characteristics by evening out hot spots and enhance product reliability.
RoHS lead solder exemption compliant
Cost-effective single board design
Low profile – 11 mm height
Input/output isolation: 1500VDC, basic
insulation
High efficiency - up to 90% at full load
Start-up into high capacitive load
Low conducted and radiated EMI
Output overcurrent protection
Output overvoltage protection
Back drive protection
Overtemperature protection
Remote sense
Set point accuracy
±
1%
Remote on/off (primary referenced), positive
or negative logic
Output voltage trim adjust, positive or
negative
UL 1950 Recognition, CSA 22.2 No. 950-95
certification, TUV IEC950
Model Selection
Model
Input
Voltage
VDC
36-75
36-75
36-75
Input
Current, Max
ADC
4.8
3.3
2.5
Output
Voltage
Vout,
VDC
5.0
3.3
2.5
Output Rated
Current
I
rated,
ADC
20
25
25
Output
Ripple/Noise,
mV p-p
150
100
100
Typical
Efficiency @
I
rated,
%
90
89
87
QLS20ZG
QLS25ZE
QLS25ZD
This product is intended for integration into end-use equipment. All the required procedures for CE marking of end-use equipment
should be followed.
SEP 12, 2003 revised to OCT 26, 2006
Page 1 of 8
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QLS25 DC-DC Series Data Sheet
25A Quarter-Brick
Absolute Maximum Ratings
Stresses in excess of the absolute maximum ratings may cause performance degradation, adversely effect long-
term reliability, and cause permanent damage to the converter.
Parameter
Input voltage
Operating Temperature
Storage Temperature
ON/OFF Control Voltage
Conditions/Description
Continuous
Transient, 100ms
PC Board Temperature
Referenced to -Vin
Min
Max
75
100
100
125
50
Units
VDC
VDC
°C
°C
VDC
-40
-40
Environmental and Mechanical Specifications
All specifications apply over specified input voltage, output load, and temperature range, unless otherwise noted.
Parameter
Shock
Sinusoidal Vibration
Weight
Water Washing
MTBF
Conditions/Description
Halfsine wave, 3 axes
GR-63-Core, Section 5.4.2
Standard process
Per Bellcore TR-NWT-000332
Min
50
1
Nom
Max
Units
g
g
Oz/g
kHrs
1.2/35
Yes
1,980
Isolation Specifications
All specifications apply over specified input voltage, output load, and temperature range, unless otherwise noted.
Parameter
Insulation Safety Rating
Isolation Voltage
Isolation Resistance
Isolation Capacitance
Conditions/Description
Min
1500
10
1100
Nom
Basic
Max
Units
VDC
MOhm
pF
Input Specifications
All specifications apply over specified input voltage, output load, and temperature range, unless otherwise noted.
Parameter
Input Voltage
Turn-On Input Voltage
Turn-Off Input Voltage
Turn-On Time
Input Reflected Ripple Current
Inrush Transient
Conditions/Description
Continuous
Ramping Up
Ramping Down
To Output Regulation Band
100% Resistive Load
Full Load, 12µH source inductance
Vin=Vin.max
60
0.1
mA p-p
A
2
s
Min
36
Nom
48
33
32
5
10
Max
75
Units
VDC
VDC
VDC
mS
SEP 12, 2003 revised to OCT 26, 2006
Page 2 of 8
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QLS25 DC-DC Series Data Sheet
25A Quarter-Brick
Output Specifications
All specifications apply over specified input voltage, output load and temperature range, unless otherwise noted.
Parameter
Output Voltage Setpoint Accuracy
Output Current*
Line Regulation
Load Regulation
Total output voltage regulation
Remote Sense Headroom
Dynamic Regulation
Peak Deviation
Settling Time
Admissible Load Capacitance
Output Current Limit Threshold**
Switching Frequency
Overvoltage Protection,
Non Latching
Trim Range
Over all input voltage and load
conditions
I
rated
, Vin=Vnom
120
90
to 1% error band
I
rated
, Nom Vin
Vout≤0.97Vout.nom
20,000
110
270
140
110
140
50-75% load step change
5
150
%Vout
μs
μF
%I
rated
kHz
%Vout
%Vout
Conditions/Description
Vin=Vin.nom, Full Load
See selection chart for I
rated
Vin.min to Vin.max, I
rated
Vin=Vin.nom, 10% to 100%I
rated
Over all input voltage, load, and
temperature conditions
-2
Min
-1
10
Nom
Max
1
100
0.2
0.2
2
0.5
Units
%Vout
%I
rated
%Vout
%Vout
%Vout
VDC
* At Iout<Iout.min, the output may contain low frequency component that exceeds ripple specifications.
** Overcurrent protection is non-latching with auto recovery.
Feature Specifications
All specifications apply over specified input voltage, output load, and temperature range, unless otherwise noted.
Parameter
Shutdown (ON/OFF)
Negative Logic
Converter ON
Source Current
Converter OFF
Open Circuit Voltage
Positive Logic
Converter ON
Open Circuit Voltage
Converter OFF
Source Current
Overtemperature
Protection
Conditions/Description
On/Off signal is low – converter is ON
-1.0
ON/OFF pin is connected to -Vin
3.5
ON/OFF pin is floating
On/Off signal is low–converter is OFF
3.5
ON/OFF pin is floating
-1.0
ON/OFF pin is connected to -Vin
Average board temperature
105
1.8
1
50
5
50
5
1.8
1
VDC
mADC
VDC
VDC
VDC
VDC
VDC
mADC
°C
Min
Nom
Max
Units
SEP 12, 2003 revised to OCT 26, 2006
Page 3 of 8
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QLS25 DC-DC Series Data Sheet
25A Quarter-Brick
Characteristic Curves
4
95
90
Efficiency, %
85
80
36V
75
70
65
0
4
8
12
Output current, A
16
20
48V
75V
Input current, ADC
3.5
3
2.5
2
1.5
1
0.5
0
0
10
20
30
40
50
Input voltage, VDC
60
70
Figure 4. QLS20ZG Input Characteristic
Figure 1. QLS20ZG Efficiency vs. Output Load
3.5
95
Input current, ADC
3
2.5
2
1.5
1
0.5
0
0
10
20
30
40
50
Input voltage, VDC
60
70
90
Efficiency, %
85
80
75
70
65
0
5
10
15
Output current, A
20
25
36V
48V
75V
Figure 5.QLS25ZE Input Characteristic
Figure 2. QLS25ZE Efficiency vs. Output Load
3.0
Input current, ADC
36V
48V
75V
95
90
Efficiency, %
85
80
75
70
65
0
5
10
15
Output current, A
20
25
2.5
2.0
1.5
1.0
0.5
0.0
0
10
20
30
40
50
60
70
Input voltage, VDC
Figure 6. QLS25ZD Input Characteristic
Figure 3. QLS25ZE Efficiency vs. Output Load
SEP 12, 2003 revised to OCT 26, 2006
Page 4 of 8
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QLS25 DC-DC Series Data Sheet
25A Quarter-Brick
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).
Typical Application
Figure 7 shows the recommended connections for
the QLS25 Series converter.
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 QLS25 Series.
Negative Trim
The QLS25 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 Figure 8.
The negative trim schematic is shown in Figure 8.
Figure 7. Typical application of QLS25 Series
The QLS25 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 QLS25 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.
Shutdown Feature Description
The ON/OFF pin in the QLS25 Series converters
functions as a normal soft shutdown. It is referenced
to the –Vin pin (see Figure 7). 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.
SEP 12, 2003 revised to OCT 26, 2006
Figure 8. QLS25 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.
R
TRIM
=
A
−
B
× Δ
V
,
kΩ
Δ
V
(1)
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