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Description
The QHS is a series of high efficiency, high-density, single output dc-dc converters for onboard conversion of
standard telecom and datacom input voltages into isolated low voltage outputs in a through-hole mounting
package. The two-board construction provides a cool environment for control components and the integrated
metallic substrate PCB provides superior thermal management for power components resulting in enhanced
product reliability. A heat sink can be conveniently and effectively attached to the IMS base plate for operations in
elevated ambient conditions or where airflow is minimal.
Model Selection
Model Input
Voltage
VDC
Input
Current, Max
ADC
Output
Voltage
Vout,
VDC
Output Rated
Current
I rated,
ADC
Output
Ripple/Noise,
mV p-p
Typical
Efficiency @
I rated, %
QHS12ZH 36-75 4.5 12.0 12 150 91
QHS25ZG 36-75 4.3 5.0 25 150 92
QHS40ZE 36-75 4.5 3.3 40 150 89
QHS40ZD 36-75 3.3 2.5 40 100 88
QHS40ZB 36-75 2.5 1.8 40 100 85
QHS50ZA 36-75 2.7 1.5 50 100 79
QHS50ZY 36-75 2.3 1.2 50 100 76
Applications
• Distributed power architectures
• Telecommunications equipment
• LAN/WAN
• Data processing
Features
• Low profile – 12.7 mm height
• Input/output isolation: 1500VDC, Basic
insulation
• High efficiency - up to 92% 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
• Remote on/off (primary referenced), positive or
negative logic
• Output voltage trim adjust
• UL1950 recognition, CSA 22.2 No. 950-95
certification, TUV IEC950
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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.
Table 1. Absolute Maximum Ratings
Parameter Conditions/Description Min Max Units
Input voltage Continuous
Transient
75
80
VDC
VDC
Operating Temperature Base Plate Temperature -40 100 °C
Storage Temperature -40 125 °C
ON/OFF Control Voltage Referenced to -Vin 20 VDC
Environmental and Mechanical Specifications
All specifications apply over specified input voltage, output load, and temperature range, unless otherwise noted.
Table 2. Environmental and Mechanical Specifications
Parameter Conditions/Description Min Nom Max Units
Shock Halfsine wave, 3 axes 50 g
Sinusoidal Vibration GR-63-Core, Section 5.4.2 1 g
Weight 1.2/35 Oz/g
Water Washing Standard process Yes
MTBF Per Bellcore TR-NWT-000332 1,980 kHrs
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Isolation Specifications
All specifications apply over specified input voltage, output load, and temperature range, unless otherwise noted.
Table 3. Isolation Specifications
Parameter Conditions/Description Min Nom Max Units
Insulation Safety Rating Basic
Isolation Voltage Input to output, input to base plate 1500 VDC
Isolation Voltage Output to base plate 500 VDC
Isolation Resistance 10 MOhm
Isolation Capacitance 1000 pF
Input Specifications
All specifications apply over specified input voltage, output load, and temperature range, unless otherwise noted.
Table 4. Input Specifications
Parameter Conditions/Description Min Nom Max Units
Input Voltage Continuous 36 48 75 VDC
Turn-On Input Voltage Ramping Up 34 VDC
Turn-Off Input Voltage Ramping Down 33 VDC
Input over voltage protection Ramping up 76 84 VDC
Turn-On Time To Output Regulation Band
100% Resistive Load
5 ms
Input Reflected Ripple Current Full Load, 12uH source inductance
60 mA p-p
Inrush Transient Vin=Vin.max 0.1 A2s
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Output Specifications
All specifications apply over specified input voltage, output load and temperature range, unless otherwise noted.
Table 5. Output Specifications
Parameter Conditions/Description Min Nom Max Units
Output Voltage Setpoint Accuracy Vin=Vin.nom, Full Load
1.8V -1.67 1.67 %Vout
2.5V -2.00 2.00 %Vout
3.3V -1.5 1.5 %Vout
12V -2.0 2.0 %Vout
Output Current* See selection chart for Irated 0 100 %Irated
Line Regulation Vin.min to Vin.max, Irated 0.2 %Vout
Load Regulation Vin=Vin.nom, 10% to 100%Irated 0.75 %Vout
Total output voltage regulation Over all input voltage, load, and
temperature conditions
-3 3 %Vout
Remote Sense Headroom*** 10% %Vout
Dynamic Regulation
Peak Deviation
Settling Time
50-75% load step change
to 1% error band
5
250
%Vout
µs
Admissible Load Capacitance Irated, Nom Vin 27,000 µF
12V 8,000
µF
Output Current Limit Threshold** Vout≤0.97Vout.nom 110 150 %Irated
Switching Frequency 2.5V and 1.8V 300 kHz
3.3V 450 kHz
12V 400 kHz
Overvoltage Protection,
Non Latching
Over all input voltage and load
conditions
120 140 %Vout
Trim Range Irated, Vin=Vnom 90 110 %Vout
* At Iout<Iout.min, the output may contain low frequency component that exceeds ripple specifications.
** Overcurrent protection is non-latching with auto recovery.
*** Vout can be increased up to 10% via the sense leads or up to 10% via the trim function, however total output voltage trim from all sources
should not exceed 10% of Vout
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Feature Specifications
All specifications apply over specified input voltage, output load and temperature range, unless otherwise noted.
Table 6. Feature Specifications
Parameter Conditions/Description Min Nom Max Units
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
On/Off signal is low – converter is ON
ON/OFF pin is connected to -Vin
ON/OFF pin is floating
On/Off signal is low–converter is OFF
ON/OFF pin is floating
ON/OFF pin is connected to -Vin
-0.5
3.5
3.5
-0.5
1.8
1
20
5
20
5
1.8
1
VDC
mADC
VDC
VDC
VDC
VDC
VDC
mADC
Overtemperature Protection Average board temperature 105 °C
Characteristic Curves
60
65
70
75
80
85
90
95
10 20 30 40 50 60 70 80 90 100
LOAD %
EFFICIENCY %
EFF.(35V)
EFF.(48V)
EFF.(75V)
Figure 1. QHS12ZH Efficiency vs. Output Load
60
65
70
75
80
85
90
95
10 20 30 40 50 60 70 80 90 100
LOAD %
EFFICIENCY %
EFF.(36V)
EFF.(48V)
EFF.(75V)
Figure 2. QHS40ZE Efficiency vs. Output Load
60
65
70
75
80
85
90
95
10 20 30 40 50 60 70 80 90 100
LOAD %
EFFICIENCY %
EFF.(36V)
EFF.(48V)
EFF.(75V)
Figure 3. QHS40ZD Efficiency vs. Output Load
55
60
65
70
75
80
85
90
10 20 30 40 50 60 70 80 90 100
LOAD %
EFFICIENCY %
EFF.(36V)
EFF.(48V)
EFF.(75V)
Figure 4. QHS40ZB Efficiency vs. Output Load
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0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0 10203040506070
Input Voltage (V)
Input Current (A)
Figure 5. QHS12ZH Input Characteristics
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0 10203040506070
Input Voltage (V)
Input Current (A)
Figure 6. QHS40ZE Input Characteristics
0
0.5
1
1.5
2
2.5
3
3.5
4
0 10203040506070
Input Voltage (V)
Input Current (A)
Figure 7. QHS40ZD Input Characteristics
0
0.5
1
1.5
2
2.5
3
0 10203040506070
Input Voltage (V)
Input Current (A)
Figure 8. QHS40ZB Input Characteristics
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Typical Application
Figure 9 shows the recommended connections for the
QHS Series converter.
+Vo
+Sense
Trim
-Sense
-Vo-Vi
+Vi
On/Off
Fuse
C1 C2 C3
QHS40ZX
Figure 9. Typical Application of the QHS Series
The QHS 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 QHS 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.
Shutdown Feature Description
The ON/OFF pin in the QHS 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.
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
Industry Standard Trim
The 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 10.
Figure 10. QHS Series Positive Trim Schematic
The equations below determine the trim resistor
value required to achieve a ∆V change in the
output voltage.
Ω
⎟
⎠
⎞
⎜
⎝
⎛−
∆
−
∆
∆+
=− k
Vo
upRadj )2.10
%
510
%225.1
%)100(1.5
Ω
⎟
⎠
⎞
⎜
⎝
⎛−
∆
=− kdownRadj )2.10
%
510
where ∆V% is the output voltage change
expressed in percents of the nominal output
voltage, Vout.
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Notes:
1. When the output voltage is trimmed up, the output power from
the converter must not exceed its maximum rating. The power is
determined by measuring the output voltage on the output pins,
and multiplying it by the output current.
2. In order to avoid creating apparent load regulation degradation, it
is important that the trim resistors are connected directly to the
remote sense pins, and not to the load or to traces going to the
load.
3. The QHS Series converters will trim down further than the 10%
limit. In general, this is permissible. The user must confirm that
the results are acceptable in the application.
Safety Considerations
The QHS Series converters feature 1500 Volt DC
isolation from input to output. The input to output
resistance is greater than 10MOhm. These converters
are provided with Basic insulation between input and
output circuits according to all IEC60950 based
standards. Nevertheless, if the system using the
converter needs to receive safety agency approval,
certain rules must be followed in the design of the
system. In particular, all of the creepage and clearance
requirements of the end-use safety requirements must
be observed. These documents include UL60950 -
CSA60950-00 and EN60950, although other or
additional requirements may be needed for specific
applications.
The QHS Series converters have no internal fuse. The
external fuse must be provided to protect the system
from catastrophic failure as shown in Figure 7. The
user can select a fuse based upon the highest inrush
transient at the maximum input voltage and the
maximum input current of the converter, which occurs
at the minimum input voltage. Both input traces and the
chassis ground trace (if applicable) must be capable of
conducting a current of 1.5 times the value of the fuse
without opening. The fuse must not be placed in the
grounded input line, if any.
In order for the output of the QHS Series converter to
be considered as SELV (Safety Extra Low Voltage) or
TNV-1, according to all IEC60950 based standards, one
of the following requirements must be met in the system
design:
• If the voltage source feeding the module is SELV or
TNV-2, the output of the converter may be
grounded or ungrounded.
• If the voltage source feeding the module is ELV, the
output of the converter may be considered SELV
only if the output is grounded per the requirements
of the standard.
• If the voltage source feeding the module is a
Hazardous Voltage Secondary Circuit, the
voltage source feeding the module must be
provided with at least Basic insulation
between the source to the converter and any
hazardous voltages. The entire system,
including the QHS converter, must pass a
dielectric withstand test for Reinforced
insulation. Design of this type of systems
requires expert engineering and under-
standing of the overall safety requirements
and should be performed by qualified
personnel.
Thermal Considerations
The QHS Series converters are designed for
natural or forced convection cooling. The
maximum allowable output current of the
converters is determined by meeting the derating
criteria for all components used in the converters.
For example, the maximum semiconductor
junction temperature is not allowed to exceed
120°C to ensure reliable long-term operation of
the converters. Contact Power-One for the
complete list of the derating criteria.
The graphs in Figures 11-14 show the maximum
output current of the QHS Series converters at
different ambient temperatures under both natural
and forced (longitudinal airflow direction, from pin
1 to pin 3) convection.
For example, from Figure 11, the QHS40ZE
operating at 55°C can deliver up to 18A reliably
with 100LFM forced air, while up to 25A reliably
with 400LFM forced air.
0
2
4
6
8
10
12
25 30 35 40 45 50 55 60 65 70 75 80 85
Ambient Temperature (C)
Output Current (A)
0
100LFM
200LFM
300LFM
400LFM
Figure 11. QHS12ZH (12V) Derating Curves
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0
5
10
15
20
25
30
35
40
25 30 35 40 45 50 55 60 65 70 75 80 85
Ambient Temp erature (C)
Output Current (A)
0
100LFM
200LFM
300LFM
400LFM
Figure 12. QHS40ZE (3.3V) Derating Curves
0
5
10
15
20
25
30
35
40
25 30 35 40 45 50 55 60 65 70 75 80 85
Ambient Temperature (C)
Output Current (A)
0
100LFM
200LFM
300LFM
400LFM
Figure 13. QHS40ZD (2.5V) Derating Curves
0
5
10
15
20
25
30
35
40
25 30 35 40 45 50 55 60 65 70 75 80 85
Ambient Temperature (C)
Output Current (A)
0
100LFM
200LFM
300LFM
400LFM
Figure 14. QHS40ZB (1.8V) Derating Curves
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Mechanical Drawing
Figure 15. Mechanical Drawing
Ordering:
Table 8. Ordering Information
Options Suffixes to add to part number
Positive- Standard, no suffix required Remote ON/OFF
Negative- Add “NT” suffix
0.18”- Standard, no suffix required
0.11”- Add “8” suffix
Pin Length
0.15”- Add “9” suffix
Notes:
Consult factory for the complete list of available options.
NUCLEAR AND MEDICAL APPLICATIONS - Power-One products are not authorized for use as critical components in life support systems,
equipment used in hazardous environments, or nuclear control systems without the express written consent of the respective divisional
president of Power-One, Inc.
TECHNICAL REVISIONS - The appearance of products, including safety agency certifications pictured on labels, may change depending on
the date manufactured. Specifications are subject to change without notice.
Pin Function
1 -Vin
2 On/off
3 +Vin
4 -Vout
5 -Sense
6 Trim
7 +Sense
8 +Vout
Mechanical Tolerances
Inches Millimeters
X.XX ±0.020 X.X ±0.5
X.XXX ±0.010 X.XX ±0.25
Pin
±0.002 ±0.05
Table 7. Pinout/Functions
