The QLS25 is a series of cost-effective, high-density single output DC-
DC converters providing on-board 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: 1500 VDC, 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
Approved to the latest edition of the following standards:
UL/CSA60950-1, IEC60950-1 and EN60950-1.
Distributed power architectures
Telecommunications equipment
LAN/WAN applications
Data processing applications
Asia-Pacific
+86 755 298 85888
Europe, Middle East
+353 61 225 977
North America
+1 866 513 2839
© 2015 Bel Power Solutions, Inc.
BCD.00736_AA
2
MODEL
QLS20ZG
QLS25ZE
QLS25ZD
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
This product is intended for integration into end-use equipment. All the required procedures for CE marking of end-use equipment should
be followed.
Model numbers highlighted in yellow or shaded are not recommended for new designs.
All specifications apply over specified input voltage, output load, and temperature range, unless otherwise noted.
PARAMETER
Absolute Maximum Ratings
1
Input Voltage
Operating Temperature
Storage Temperature
ON/OFF Control Voltage
Referenced to -Vin
Continuous
Transient, 100ms
PC Board Temperature
-40
-40
75
100
100
125
50
VDC
VDC
°C
°C
VDC
CONDITIONS / DESCRIPTION
MIN
NOM
MAX
UNITS
Isolation Characteristics
Insulation Safety Rating
Isolation Voltage
Isolation Resistance
Isolation Capacitance
1500
10
1100
Basic
VDC
MΩ
pF
Feature Characteristics
Shutdown (ON/OFF) Negative Logic
Converter ON
Source Current
Converter OFF
Open Circuit Voltage
Shutdown (ON/OFF) Positive Logic
Converter ON
Open Circuit Voltage
Converter OFF
Source Current
Overtemperature Protection
ON/OFF pin is connected to -Vin
Average Board Temperature
105
ON/OFF pin is floating
-1
ON/OFF pin is floating
On/Off signal is low –converter is OFF
3.5
50
5
1.8
1
VDC
VDC
VDC
mADC
°C
ON/OFF pin is connected to -Vin
3.5
On/Off signal is low – converter is ON
-1.0
1.8
1
50
5
VDC
mADC
VDC
VDC
Input Characteristics
Operating Input Voltage Range
Turn-On Input Voltage
Turn-Off Input Voltage
Continuous
Ramping Up
Ramping Down
36
48
33
32
75
VDC
VDC
VDC
tech.support@psbel.com
3
Turn-On Time
Input Reflected Ripple Current
Inrush Transient
To Output Regulation Band
100% Resistive Load
Full Load, 12µH source inductance
Vin=Vin.max
5
10
60
0.1
ms
mA p-p
A
2
s
Output Characteristics
Output Voltage Setpoint Accuracy
Output Current Range
2
Line Regulation
Load Regulation
Total output voltage regulation
Remote Sense Headroom
Dynamic Regulation
Peak Deviation
Settling Time
Admissible Load Capacitance
Output Current Limit Threshold
3
Switching Frequency
Overvoltage Protection,
Non Latching
Trim Range
Overall 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
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
-1
10
1
100
0.2
0.2
2
0.5
%Vout
%I
rated
%Vout
%Vout
%Vout
VDC
Enviromental and Mechanical
Weight
1.2/35
GR-63-Core, Section 5.4.2
1
50
Yes
Oz/g
g
g
Sinusoidal Vibration
Shock
Water Washing
Halfsine wave, 3 axes
Standard process
Reliability
MTBF
1
Per Bellcore TR-NWT-000332
1,980
kHrs
Stresses in excess of the absolute maximum ratings may cause performance degradation, adversely effect long-term reliability, and
cause permanent damage to the converter
2
At Iout<Iout.min, the output may contain low frequency component that exceeds ripple specifications.
3
Overcurrent protection is non-latching with auto recovery.
tech.support@psbel.com
4
Figure 1 shows the recommended connections for the QLS25 Series converter.
Figure 1. 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<0.7 is recommended for the QLS25 Series.
Refer to the “Inrush Current Control Application Note” on
belpowersolutions.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.
The ON/OFF pin in the QLS25 Series converters functions as a normal soft shutdown. It is referenced to the –Vin pin (see
Figure 1). 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).
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.
tech.support@psbel.com
5
2.4
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 Fig.2.
The negative trim schematic is shown in Figure 2.
Figure 2. 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
½
A
B
V
V
,
[kΩ]
(1)
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.
MODEL
TRIM UP
A
QLS20ZG
QLS25ZE
QLS25ZD
3.77
2.07
1.27
B
6.81
3.92
3.92
TRIM DOWN
A
11.58
3.5
1.31
B
9.88
5.61
4.95
tech.support@psbel.com
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