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Applications
• Base station amplifiers
• Distributed power architectures
• Telecommunications equipment
• LAN/WAN applications
• Data processing applications
Features
• Low profile – 12.7 mm height
• Input-to-output isolation: 1500VDC
• Basic insulation
• High efficiency - up to 93% at full load
• Tight dynamic load response
• Output overcurrent protection
• Output overvoltage protection
• Overtemperature protection
• Remote sense
• Remote on/off (primary referenced), positive
or negative logic option
• Output voltage trim adjust, positive or
negative option
• UL 1950 Recognition, CSA 22.2 No. 950-95
certification, TUV IEC950
Description
The FHS Series power modules are dc-dc converters that operate over an input voltage range of 36 to 75VDC and
provide a regulated DC output voltage at up to 18 amps of output current. The output is fully isolated from the
input, which allows a positive or negative output configuration.
The open-frame module is constructed with a two-board approach. The power devices are connected to an
Insulated Metal Substrate (IMS) base plate, which provides very low thermal impedance. A separate PCB is
populated with the control circuitry and is physically isolated from the hotter IMS board. This approach allows for
lower component temperatures, hence increased reliability. The standard feature set includes remote on/off,
remote output voltage sensing, negative logic output trim (optional positive logic output trim available1), input under
and overvoltage lockout and overtemperature shutdown with hysteresis.
Model Selection
Model Input
voltage
(VDC)
Input
current, Max,
(ADC)
Output
voltage
(VDC)
Output rated
current
I rated, (ADC)
Output
Ripple/Noise
(mV p-p)
Typical
Efficiency
@ I rated, (%)
FHS18Z28 36-75 16 28 18 150 93
This product is intended for integration into end-use equipment. All the required procedures for CE marking of end-use
equipment should be followed.
1 Consult factory for availability.
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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.
Parameter Conditions/Description Min Max Units
Input voltage Continuous
Transient, 100ms
75
100
VDC
VDC
Operating Temperature Baseplate Temperature -40 110 °C
Storage Temperature -55 125 °C
ON/OFF Control Voltage Referenced to -Vin 7 VDC
Output Power 504 W
Environmental and Mechanical Specifications
All specifications apply over specified input voltage, output load, and temperature range, unless otherwise noted.
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 5.4/152 Oz/g
Water Washing Standard process Yes
MTBF Per Bellcore TR-NWT-000332 1,000 kHrs
Isolation Specifications
All specifications apply over specified input voltage, output load, and temperature range, unless otherwise noted.
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 1500 VDC
Isolation Resistance 10 MOhm
Isolation Capacitance 1000 pF
Safety Regulatory Compliance
Safety Agency Standard Approved To: Marking
Underwriters Laboratories UL60950/CSA60950-00 cULus
TUV product Service TUV EN60950:2000 TUV PS Baurt mark
CB report IEC60950:1999 N/A.
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Input Specifications
All specifications apply over specified input voltage, output load, and temperature range, unless otherwise noted.
Parameter Conditions/Description Min Nom Max Units
Input Voltage Continuous 36 48 75 VDC
Turn-On Input Voltage Ramping Up 1 32 34 36 VDC
Turn-Off Input Voltage Ramping Down 1 30 32 34 VDC
Turn On/Off Hysteresis 1.5 VDC
Input over voltage protection Turn-Off threshold 76 80 84 VDC
Input Reflected Ripple Current Full Load, 12µH source inductance
BW=20MHz 2
60 mAP-P
Inrush Transient Vin=Vin.max 0.1 A2s
1 Refer to Fig. 2 for waveform.
2 Refer to Fig. 10 for Test measurement circuit.
Output Specifications
All specifications apply over specified input voltage, output load, and temperature range, unless otherwise noted.
Parameter Conditions/Description Min Nom Max Units
Output Voltage Setpoint Accuracy Vin=Vin.nom, Full Load 27.44 28 28.56 Vdc
Output Current 1.8 18 A
Line Regulation Vin.min to Vin.max, IRATED-MAX 0.2 0.5 %Vout
Load Regulation Vin=Vin.nom, 10% to 100%Irated 0.5 1.0 %Vout
Output Temperature Regulation TBaseplate = -40OC to +110OC) 0.02 %Vo/OC
Ripple and Noise, DC to 20MHz 1,2 Over line and load
Tamb= 0°C to 85°C
150
30
mVP-P
mVRMS
Dynamic Regulation
Peak Deviation
Settling Time
50-75% load step change
to 1% error band
700
250
800
750
mV
µs
Output Turn-On Time 3 To 97% VoNOM 15 25 ms
Admissible Load Capacitance IRATED, resistive load, VinNOM 100
µF/A
Backdrive Protection No damage to converter Yes
Switching Frequency 400 kHz
1 At Iout<Iout-min, the output may contain low frequency component that exceeds ripple specifications.
2 See Figure 11 for test setup
3 Refer to fig. 3
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Protections Specifications
All specifications apply over specified input voltage, output load, and temperature range, unless otherwise noted.
Parameter Conditions/Description Min Nom Max Units
Overcurrent Protection
Type Non-latching, auto-recovery
Threshold 20 23 29 A
Short Circuit Hiccup-type 1 15 ARMS
Overvoltage Protection 2
Type Clamping / Hiccup, auto-recovery
Threshold All Vin and Io conditions 115 140 % Vout
Overtemperature Protection
Type Non-latching, auto-recovery
Threshold Baseplate temperature 120 130
°C
Recovery 90 °C
1 Refer to Fig. 4 2 Refer to Fig. 5
Feature Specifications
All specifications apply over specified input voltage, output load, and temperature range, unless otherwise noted.
Parameter Conditions/Description Min Nom Max Units
ON/OFF 1
Negative Logic (-N suffix)
Converter ON
Source Current
Converter OFF
Open Circuit Voltage
ON/OFF signal is low or the pin is
connected to -Vin – converter is ON
Von/off in reference to -Vin
ON/OFF pin is connected to -Vin
Von/off in reference to -Vin
ON/OFF pin is floating
-0.5
2.5
0.5
0.8
1
7
5
VDC
mADC
VDC
VDC
Positive Logic (no suffix)
Converter ON
Open Circuit Voltage
Converter OFF
Source Current
On/Off signal is low or the pin is floating
–converter is OFF
Von/off in reference to -Vin
ON/OFF pin is floating
Von/off in reference to -Vin
ON/OFF pin is connected to -Vin
2.5
-0.5
0.5
7
5
0.8
1
VDC
VDC
VDC
mADC
Remote Sense 2
Remote Sense Headroom 5 %Vout
Output Voltage Trim 2
Trim Up Vin = Vin-nom, Iout=Irated 10 %
Trim Down Vin = Vin-nom, Iout=Irated -10 %
1 Additional information located on page 6.
2 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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Efficiency Characteristics
FHS18Z28. EFF. VS. LOAD
40
45
50
55
60
65
70
75
80
85
90
95
100
10 20 30 40 50 60 70 80 90 100
LOAD %
EFFICIENCY
%
EFF.(36V) EFF.(48V) EFF.(75V)
Figure 1. FHS18Z28 Efficiency vs. Output Load
Input Turn-On / Off Operation
Input Current vs. Voltage
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
0 1020304050607080
Input Voltage (V)
Input Current (A)
Turn On
Voltage
Threshold
Turn Off
Voltage
Threshold
Figure 2. FHS18Z28 Input UVLO Characteristics
Turn-on Waveform
Figure 3. Output Voltage turn-on FHS18Z28
Conditions: Vin=48V, Load: full, , Co=none
(Note: monotonic rise characteristic)
Short Circuit Operation
Figure 4. Output Current with Shorted Output Pins,
Vin = 75Vdc, Scale is 20Amp/Div.
(Actual amplitude: 10.8ARMS)
Once the output current is brought back into its
specified range, the converter automatically exits
the hiccup mode and continues normal operation.
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OVP Operation
Figure 5. Output Voltage Under OVP Condition,
Vin = 75Vdc, Min Load. Scale is 10V/Div.
(Actual amplitude: 34VPEAK)
Typical Application
Figure 6 shows the recommended connections for
the FHS Series converter.
+Vo
+Sense
Trim
-Sense
-Vo-Vi
+Vi
On/Off
Fuse
C1 C2 C3
FHSXXZX
Figure 6. Typical Application of the FHS Series
FHS 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 100µF electrolytic capacitor with the
ESR<0.7Ω is recommended.
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 FHS Series converters
functions as a normal soft shutdown. It is
referenced to the –Vin pin or signal ground (see
Figure 6). With the positive logic, when the
ON/OFF pin is pulled low, the output is turned off
and the unit exhibits very low input current.
With negative logic (which is denoted by the suffix
“–N” in the part number), 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).
Remote Sense
The FHS Series converters have the capability to
remotely sense both lines of the output. This
feature moves the effective output voltage
regulation point from the output of the unit to the
point of connection of the remote sense pins. This
feature automatically adjusts the output voltage of
the converter in order to compensate for voltage
drops in distribution and maintain a regulated
voltage at the point of load. This is shown in
Figures 6, 7 & 8.
If the remote sense feature is not to be used, the
sense pins should be connected locally. The
+Sense (or Vsense) pin should be connected to the
+Vout pin directly at the output of the converter and
the –Sense (Vsense RTN) pin should be connected
to the -Vout pin directly at the output of the
converter.
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If sense pins are not connected to the load, or the
respective output pins, the converter will not be
damaged, but may not meet the output voltage
regulation specifications.
Output Voltage Trim
The trim feature allows the user to adjust the output
voltage from the nominal value. This can be used to
compensate for distribution drops, perform margining
in production, or accommodate other requirements
when output voltage needs to be adjusted from the
nominal value. There are two trim options available.
Optional Positive Trim (suffix –T)
The -T option units trim up with a resistor from the
TRIM pin to the (+)Vsense pin and trim down with a
resistor from the TRIM pin to the (-)Vsense RTN pin
as shown in Figure 7.
Figure 7. FHS Series Positive Trim Schematic (-T)
The equations below determine the trim resistor
value required to achieve a ∆% change in the output
voltage.
Ω
⎟
⎠
⎞
⎜
⎝
⎛−
∆
−
∆
∆+
=− k
Vonom
upRadj )2.42
%
510
%
%)100(17.4
Ω
⎟
⎠
⎞
⎜
⎝
⎛−
∆
=− kdownRadj )2.42
%
510
where ∆% is the output voltage change expressed
in percent of the nominal output voltage, Vout.
(example: to trim up or down by 5% of Vo nominal,
∆% = 5)
Negative Logic Trim (no P/N suffix)
The negative logic trim unit trims down with a
resistor from Trim to Vsense, and trims up with a
resistor from Trim to VsenseRTN (see figure 8).
Figure 8. FHS Series Negative Trim Schematic
The equations below determine the trim resistor
value required to achieve a new output voltage.
Ω
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛−
−−
=− k
Voadj
upRadj 20
1))225.1/(4.54*225.1/(49.2
49.2
Ω
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛−
−−
=− k
Voadj
downRadj 20
1))225.1(03.2/(4.54
4.54
where Voadj is the desired output voltage
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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 FHS 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 FHS Series converters feature 1500 Volt DC
isolation from input to output. The input-to-output
resistance is greater than 10MΩ. 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 FHS Series converters have no internal fuse.
The external fuse must be provided to protect the
system from catastrophic failure as shown in Figure
6. The fuse with a rating not greater than 20A is
recommended. The user can select a lower rating
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 FHS 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 FHS
converter, must pass a dielectric withstand test
for Reinforced insulation. Design of this type of
systems requires expert engineering and
understanding of the overall safety
requirements and should be performed by
qualified personnel.
Thermal Considerations
FHS 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 125°C to ensure reliable long-term
operation of the converters. Contact Power-One for
the complete list of the derating criteria.
Figure 9 shows the maximum output current of the
FHS Series at different ambient temperatures under
both natural and forced (longitudinal airflow
direction, from pin 1 to pin 4) convection.
THERMAL DERATING CURVE
Vin = 54V, Orientation : Vin- to Vin +
0
5
10
15
20
25 40 55 70 85
Ambient Temperature (Deg C)
Load Current (A)
NC (25 - 35 LFM) 100 LFM 200 LFM 300 LFM 400 LFM
FHS18Z28
Data Rev: 01
Figure 9. FHS18Z28 Derating Curves
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Test Configurations
. Figure 10. Input Reflected Ripple Current Test Setup
Note: Measure input reflected-ripple current with a simulated
inductance (Ltest) of 12 µH. Capacitors offset possible battery
impedance. Measure current as shown above.
To improve accuracy and repeatability of output
ripple and noise measurements, Power-One utilizes
the test setup shown in Figure 11.
DUT
LOAD1
0.1uf
ceramic SCOPE
COPPER STRIPS (2 to 3 i nches)
+Vo1
-Vo1
10uF
Tantalum
Figure 11. Output Ripple and
Noise Measurement Test Setup
A BNC connector is used for the measurements to
eliminate noise pickup associated with long ground
leads of conventional scope probes. The
connector, a 0.1µF ceramic and a 10µF tantalum
capacitors, and the load are located 2-3” away from
the converter.
BATTER
Y
Cs 220 uF
ESR < 0.1 OHM
@ 20 ºC, 100
kHz
Ltest
12 uH
22 uF
ESR < 0.7 OHM
@ 20 ºC, 100 kHz
Vi(+)
Vi(-)
TO OSCILLOSCOPE
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Conducted EMI (Line)
FHS18Z28
C1
Vin+
Vin-
+
-
VIN
LOAD1
C2
FC100V20A
CASEGND
C3 C4
C5 C6
Vo1
-Vo1
Ref. Des Description Manufacture
C1, 2 0.47µF @100V MLC Capacitor (1812) AVX or Equivalent (Equiv.)
C3 100µF @ 100V Alum. Electrolytic Capacitor Nichicon NRSZ Series or Equiv.
C4 22µF@ 100V Alum. Electrolytic Capacitor United Chemicon KMG Series or Equiv.
C5, 6 0.01µF MLC Capacitor AVX or Equiv.
F1 FC100V20A Input Filter Module Power-One
Figure 12. Recommended Filter Configuration
(to meet CISPR 22 Class A for Conducted Emissions)
The above circuit and component values are offered as a guide. Performance results vary depending on
circuit layout techniques, proximity to noise emitting components and conductor traces and other variables
of the specific application. Verification of compliance must be performed.
Figure 13. Measured Performance Characteristics
CISPR 22 Class A for Conducted Emissions
Vin=48Vdc, Io=18Amps
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Mechanical Drawing
Ordering Information
Notes:
1 Consult factory for availability.
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 +Vin
3 Sgnd
4 On/off
5, 6, 7 Vout
8,9,10 -Vout
11 -Sense
12 +Sense
13 Trim
14 NU
15 IOG
Options Suffixes to add to part number
Positive- Standard, no suffix required Remote ON/OFF
Negative- Add “N” suffix
Negative- No suffix required Trim
Positive - Add “T” suffix 1
0.18”- Standard, no suffix required
0.11”- Add “8” suffix 1
Pin Length
0.15”- Add “9” suffix 1
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