www.murata-ps.com
www.murata-ps.com/support
For full details go to
www.murata-ps.com/rohs
UEI15 Series
Isolated Wide Input Range 15-Watt DC/DC Converters
MDC_UEI15W.C11 Page 1 of 17
Featuring a full 15 Watt or greater output in one square inch of board area, the UEI
series isolated DC/DC converter family offers effi cient regulated DC power for printed
circuit board mounting.
GATE DRIVE
Control
Reference, Trim &
Error Amplifier
+VIN
−VIN
+VOUT
–VOUT
On/Off
Control
TRIM
ISOLATION BARRIER
ISOLATION
Typical topology is shown.Figure 1. Simplifi ed block diagram—3.3V and 5VOUT models only.
Typical unit
FEATURES
Small footprint DC/DC converter, ideal for
high current applications
Industry standard 0.96" x 1.1" X 0.32" open
frame package and pinout
Wide range input voltages 9-36 and 18-75 Vdc
Assembly and attachment for RoHS standards
Isolation up to 2250 VDC (basic)
Up to 15 Watts or greater total output power
with overtemperature shutdown
High effi ciency synchronous rectifi er forward
topology
Stable operation with no required external
components
Usable -40 to 85°C temperature range (with
derating)
Certifi ed to UL 60950-1, CAN/CSA-C22.2 No.
60950-1, IEC60950-1, EN60950-1 safety ap-
provals, 2nd edition
Extensive self-protection shut down features
PRODUCT OVERVIEW
Wide range 4:1 inputs on the 0.96" x 1.1" x 0.32"
converter are either 9 to 36 Volts DC (Q12 models)
or 18 to 75 Volts DC (Q48 models), ideal for battery-
powered and telecom equipment. The industry-
standard pinout fi ts larger 1" x 2" converters. Fixed
output voltages from 3.3 VDC to 15 VDC are regu-
lated to within ±0.2% or less and may be trimmed
within ±10% of nominal output. Applications
include small instruments, area-limited microcon-
trollers, computer-based systems, data communi-
cations equipment, remote sensor systems, vehicle
and portable electronics.
The UEI 15W series includes full magnetic and
optical isolation up to 2250 Volts DC (basic insula-
tion). For connection to digital systems, the outputs
offer fast settling to current step loads and toler-
ance of higher capacitive loads. Excellent ripple
and noise specifi cations assure compatibility to
circuits using CPU’s, ASIC’s, programmable logic
and FPGA’s. For systems requiring controlled
startup/shutdown, an external switch, transis-
tor or digital logic may be used to activate the
remote On/Off control.
A wealth of self-protection features avoid both
converter and external circuit problems. These
include input undervoltage lockout and overtem-
perature shutdown. The outputs current limit using
the “hiccup” autorestart technique and the outputs
may be short-circuited indefi nitely. Additional
features include output overvoltage and reverse
conduction elimination.
The high effi ciency offers minimal heat buildup
and “no fan” operation.
REG.-Nr. D806
PART NUMBER STRUCTURE
www.murata-ps.com/support
UEI15 Series
Isolated Wide Input Range 15-Watt DC/DC Converters
MDC_UEI15W.C11 Page 2 of 17
➀ Please refer to the part number structure for additional options and complete
ordering part numbers.
➁ All specifi cations are typical at nominal line voltage and full load, +25 deg.C. unless
otherwise noted. See detailed specifi cations.
➂ Minimum output load for all models is 10% of maximum current.
➃ RoHS-6 compliance does not claim EU RoHS exemption 7b (lead in solder).
PERFORMANCE SPECIFICATIONS SUMMARY AND ORDERING GUIDE ➀
Root Models ➀
Output Input
Effi ciency
Open Frame
Package – C75
VOUT
(V)
IOUT
(A)e
Power
(W)
R/N (mVp-p) ➁Regulation (Max.)
VIN
Nom.
(V)
Range
(V)
IIN =
no
load
(mA)
IIN =
full
load
(A)Typ. Max. Line Load Min. Typ. (inches) (mm)
Case
Pinout
UEI15-033-Q12 3.3 4.5 14.85 60 90 ±0.05% ±0.1% 24 9-36 43 0.71 86.5% 89%
1.1×0.96×0.32 27.9×24.4×8.1 P85
UEI15-033-Q48 3.3 5 16.5 60 90 ±0.2% ±0.2% 48 18-75 24 0.4 85.5% 88%
UEI15-050-Q12 5 3 15 70 125 ±0.05% ±0.075% 24 9-36 41 0.72 86.3% 87.3%
UEI15-050-Q48 5 3 15 60 95 ±0.05% ±0.06% 48 18-75 28 0.36 84.3% 86.0%
UEI15-120-Q12 12 1.3 15.6 110 150 ±0.05% ±0.05% 24 9-36 15 0.77 82.3% 84.5%
UEI15-120-Q48 12 1.3 15.6 85 120 ±0.0 75% ±0.05% 48 18-75 15 0.38 83.3% 85%
UEI15-150-Q12 15 1.1 16.5 130 175 ±0.05% ±0.05% 24 9-36 18 0.81 83.5% 85%
UEI15-150-Q48 15 1.1 16.5 80 120 ±0.05% ±0.05% 48 18-75 14 0.4 83.3% 85.3%
Nominal Output Voltage
in Tenths of a Volt
Unipolar Wide Input
15-Watt Series
UEI15 -Q12
--
033 P M
On/Off Control Logic:
P = Positive
N = Negative
Surface Mount Option
Blank = Standard through-hole pin mount version
M = SMT version (MSL rating 2)
CRoHS-6 Hazardous
Substance Compliance (note 4)
Input Voltage Range
Q12 = 9-36V
Q48 = 18-75V
Lx
Pin Length Option
Blank = Std. pin length 0.25˝ (6.3mm)
L1 = 0.110˝ (2.79mm)*
L2 = 0.145˝ (3.68mm)*
SPECIAL MODEL NUMBERS:
UEI-31204-C, Restricted AVL and surface mount
H
Conformal Coating Option
Blank = No coating, standard
H = Coating added, optional
(Built to order; contact Murata Power Solutions for MOQ and lead times.
Not available on SMT models.)
*Special quantity order is required;
no sample quantities available.
Note:
Some model number combinations
may not be available. Please contact
Murata Power Solutions.
www.murata-ps.com/support
UEI15 Series
Isolated Wide Input Range 15-Watt DC/DC Converters
MDC_UEI15W.C11 Page 3 of 17
cRemove overload for recovery.
MISCELLANEOUS CHARACTERISTICS
Model Family
Current Limit
Inception 98% of
Vout, after warmup
A
Short
Circuit
Protection
Method
Short
Circuit
Current
A
Short Circuit
Duration
(output shorted
to ground)➀
Pre-
biased
setup
Calculated
MTBF
Hours ➃
Operating Temperature Range Storage
Temperature
Range
ºC
Thermal
protection/
shutdown
ºC
See
Derating
Curves
UEI15-033-Q12 6.0
Current
limiting,
hiccup
autorestart
0.3 Continuous Monotonic
2 x 106
–40 to +85ºC –55 to +125 ºC
115
UEI15-033-Q48 7.2 3.49 x 106
UEI15-050-Q12 4.6
2 x 106
UEI15-050-Q48 4.5
UEI15-120-Q12 2.0
UEI15-120-Q48 1.8 4.1 x 106135
UEI15-150-Q12 1.6 2.1 x 106
115
UEI15-150-Q48 1.7 2 x 106
17
INPUT CHARACTERISTICS
Model Family
Start-up
threshold
V
Under-
voltage
Shut-
down
V
Refl ected
(back)
Ripple
Current
mA pk-pk
Input Current Recom-
mended
Fast-blow
Fuse
A
Internal
Input
Filter
Type
Reverse
Polarity
Protec-
tion
Remote On/Off Control
Inrush
Transient
A2sec
Min.
Load
mA
Output Short
Circuit
mA
Low Line
A
Standby
Mode
mA
On/Off
Current
mA
Positive Logic
blank model
suffi x
Negative Logic
"N" model
suffi x
UEI15-033-Q12 9.1 8.6
30 0.05
100
50
1.86
1
4
C
None.
Install
external
fuse. See
note 15.
1
OFF=Gnd pin
or –0.7 to +0.7V
max. ON=open
pin or +10 to
+15V max.
OFF=open pin
or +10 to +
15V max.
ON=Gnd pin
or –0.7 to
+0.8V max.
UEI15-033-Q48 16.7 15.6 65 1.03 2
UEI15-050-Q12 9.5 8.5 105 1.90 4
UEI15-050-Q48 16.7 15.6 60 0.96 2 L
UEI15-120-Q12 9.5 8.4 110 2.04 4
C
UEI15-120-Q48 16.7 15.6 56 1.02 1.5
UEI15-150-Q12 9.5 8.4 130 2.13 4
UEI15-150-Q48 16.7 16.2 60 1.06 2
OUTPUT CHARACTERISTICS
Model Family
IOUT
Max.
mA
VOUT
Accuracy
50% Load
% of VNOM
Adjustment
Range
% of VNOM
Temperature
Coeffi cient
% of VOUT /ºC
Capacitive Loading Max.
Low ESR <0.02Ω Max,
μF
Overvoltage protection
V
OV
protection
method
Voltage Out-
put Range
Ripple/Noise
(20 MHz
bandwidth)8
Line/Load
Regulation
Effi ciency
UEI15-033-Q12
See
Ordering
Guide
(Minimum
load is 10%
of Imax)
±1 ±10 ±0.02
1,000
4.5
Magnetic
feedback See ordering guide
UEI15-033-Q48 3.9
UEI15-050-Q12 5.9
UEI15-050-Q48
470
5.9
UEI15-120-Q12 14.1
UEI15-120-Q48 15
UEI15-150-Q12 19.5
UEI15-150-Q48 20
ISOLATION CHARACTERISTICS
Model Family
Input to
Output Min.
Vdc
Isolation
Resistance
Min.
MΩ
Isolation
Capacitance
pF
Isolation
Safety
Rating
UEI15-033-Q12 2000 10 1000
Basic
insulation
UEI15-033-Q48 2250 10 1500
UEI15-050-Q12 2000 10 1500
UEI15-050-Q48 2250 10 1000
UEI15-120-Q12 2000 10 1000
UEI15-120-Q48 2250 10 1000
UEI15-150-Q12 2000 10 1500
UEI15-150-Q48 2250 10 1000
18
18
18
18
19
FUNCTIONAL SPECIFICATIONS
DYNAMIC CHARACTERISTICS
Model Family
Dynamic Load
Response
(50-75-50%
load step) μSec
to 1% VOUT ➀
Peak
Deviation
mV
Start-up Time
Switching
Frequency
KHz
VIN to VOUT regulated
(Max.) mSec
Remote On/Off to VOUT
regulated max.) mSec
UEI15-033-Q12 150 ±125
50 50
350
UEI15-033-Q48
100
±35 350
UEI15-050-Q12 ±60 350
UEI15-050-Q48 ±30 375
UEI15-120-Q12 150 ±150 340
UEI15-120-Q48
100
±200 350
UEI15-150-Q12 ±125 340
UEI15-150-Q48 ±175 380
www.murata-ps.com/support
UEI15 Series
Isolated Wide Input Range 15-Watt DC/DC Converters
MDC_UEI15W.C11 Page 4 of 17
Absolute Maximum Ratings
Absolute maximums are stress ratings. Exposure of devices to greater than any
of these conditions may adversely affect long-term reliability. Proper operation
under conditions other than those listed in the Performance/Functional Specifi -
cations is neither implied nor recommended.
(4) Mean Time Before Failure is calculated using the Telcordia (Belcore) SR-
332 Method 1, Case 3, ground fi xed conditions, Tpcboard=+25 deg.C, full load,
natural air convection.
(5) The On/Off Control is normally controlled by a switch. But it may also be
driven with external logic or by applying appropriate external voltages which are
referenced to Input Common. The On/Off Control Input should use either an open
collector or open drain transistor.
(6) Output current limiting begins when the output voltage degrades
approximately 2% from the selected setting.
(7) The outputs are not intended to sink appreciable reverse current. This may
damage the outputs.
(8) Output noise may be further reduced by adding an external fi lter. See I/O Fil-
tering and Noise Reduction.
(9) All models are fully operational and meet published specifi cations, including
“cold start” at –40°C.
(10) Regulation specifi cations describe the deviation as the line input voltage
or output load current is varied from a nominal midpoint value to either extreme.
(11) The output overvoltage protection is automatic recovery after fault
removal. The overvoltage may occur either from internal failure or from an
external forcing voltage as in a shared power system.
(12) Output current limit and short circuit protection is non-latching. When the
overcurrent fault is removed, the converter will immediately recover.
(13) Do not exceed maximum power specifi cations when adjusting the output
trim.
(14) At zero output current, the output may contain low frequency components
which exceed the ripple specifi cation. The output may be operated indefi nitely
with no load.
(15) If reverse polarity is accidentally applied to the input, to ensure reverse in-
put protection with full output load, always connect an external input fuse in series
with the +VIN input. Use approximately twice the full load input current rating at
minimum input voltage.
(16) “Hiccup” operation repeatedly attempts to restart the converter with a
brief, full-current output. If the overcurrent condition still exists, the restart current
will be removed and then tried again. This short current pulse prevents over-
heating and damaging the converter. Once the fault is removed, the converter
immediately recovers normal operation.
(17) On model UEI15-050-Q48, if VIN <20V, output trim may only be adjusted
downwards from +5.0V (more negative).
(18) Typical values shown. For minimum and maximum values see table below.
CAUTION: This product is not internally fused. To comply with safety
agency certifi cations and to avoid injury to personnel or equipment, the user
must connect an external fast-blow fuse to the input terminals. See fuse
information.
(19) All models require 10% of Imax minimum output load to meet specifi -
cations. However, they will not be damaged at zero output load.
SPECIFICATION NOTES
(1) All models are tested and specifi ed with external capacitors listed in the
table below. The external capacitors listed below are ONLY for establishing test
specifi cations. They are required for our test fi xtures and equipment. Your applica-
tion may not need them. The converter is stable with no external capacitors but
Murata Power Solutions strongly recommends external caps. All caps are low-ESR
types. Where two or more capacitors are listed, these are connected in parallel. All
caps should mount close to the DC/DC using short leads.
All specifi cations are typical unless noted. General conditions for Specifi ca-
tions are +25 deg.C, VIN=nominal, VOUT=nominal, full load. Adequate airfl ow must
be supplied for extended testing under power.
(2) Input Ripple Current is tested and specifi ed over a 5 Hz to 20 MHz band-
width. Input fi ltering is CIN=33 μF, 100V tantalum, CBUS=220 μF, 100V electro-
lytic, LBUS=12 μH.
(3) Note that Maximum Power Derating curves indicate an average current at
nominal input voltage. At higher temperatures and/or lower airfl ow, the DC/DC
converter will tolerate brief full current outputs if the total RMS current over time
does not exceed the Derating curve. All Derating curves are presented at sea level
altitude. Be aware of reduced power dissipation with increasing density altitude.
ABSOLUTE MAXIMUM RATINGS
Input
Voltage
Q12 models Volts Max. continuous 36 VDC
Volts, transient 100mS 50 VDC
Q48 models Volts Max. continuous 75 VDC
Volts, transient 100mS 100 VDC
On/Off control,
referred to –VIN
Volts, Min. –0.3
Volts, Max. 15
Input Reverse Polarity Protection See fuse section
Output Overvoltage, Volts Max. VOUT nom. +20%
Output Current, sustained short circuit Current-limited, see specs
Storage Temperature Range, Min. ºC -55
Max. ºC +125
INPUT/OUTPUT EXTERNAL TEST CAPACITORS
Model Input Capacitor Output Capacitor(s)
UEI15-033-Q12 100 μF 1 μF & 10 μF
UEI15-033-Q48 4.7 μF ceramic 1 μF & 10 μF
UEI15-050-Q12 100 μF 1 μF & 10 μF
UEI15-050-Q48 4.7 μF ceramic 1 μF & 10 μF
UEI15-120-Q12 100 μF 1 μF & 10 μF
UEI15-120-Q48 4.7 μF ceramic 1 μF & 10 μF
UEI15-150-Q12 100 μF 1 μF & 10 μF
UEI15-150-Q48 4.7 μF ceramic 1 μF & 10 μF
Root Models Conditions Minimum Typical Maximum Units
All UEI15 Q12 Start up at –40°C 10 10.5 11 Vdc
Root Models Conditions Minimum Maximum Units
All UEI15 Q12 @+25°C 8.8 10 Vdc
www.murata-ps.com/support
PERFORMANCE DATA
UEI15 Series
Isolated Wide Input Range 15-Watt DC/DC Converters
MDC_UEI15W.C11 Page 5 of 17
Maximum Current Temperature Derating @sea level
(VIN = 24V, airfl ow from input to output)
Maximum Current Temperature Derating @sea level
(VIN = 48V, airfl ow from input to output)
Maximum Current Temperature Derating @sea level
(VIN = 12V or 24V, airfl ow from input to output)
3
.
5
0
3
.
7
0
3
.
9
0
4
.
1
0
4
.
3
0
4
.
5
0
4
.
7
0
4
.
9
0
5
.
1
0
4
0
4
5
5
0
5
5
6
0
6
5
7
0
7
5
8
0
8
5
A
m
A
A
b
i
e
n
t
T
e
m
p
e
r
a
t
u
r
e
(
°C
)
O
u
t
p
u
t
C
urrent
(
A
mps
)
N
a
tural Convection
a
a
0.5 m/s (100
L
F
M
)
1.0 m/s (200
L
F
M)
(
1.5 m/s (300
L
F
)
M)
3
.
8
0
4
.
0
0
4
.
2
0
4
.
4
0
4
.
6
0
4
.
8
0
5
.
0
0
5
.
2
0
4
0
4
5
5
0
5
5
6
0
6
5
7
0
7
5
8
0
8
5
A
m
A
A
b
i
e
n
t
t
e
m
p
e
r
a
t
u
r
e
(°C)
O
u
t
p
u
t
Cu
rr
e
nt
(
A
(
(
mps
)
N
a
tural Convection
a
a
0
.5 m/s (100
L
F
M
)
1.0 m/s (200
L
F
M
)
1.5 m/s (300
L
F
M
)
(
2
.0 m
/
s
(
400
L
F
)
M)
2
.
0
2
.
5
3
.
0
3
.
5
4
.
0
4.
5
5
.
0
5
.
5
4
0
4
5
5
0
5
5
6
0
6
5
7
0
7
5
8
0
8
5
A
m
A
A
b
i
e
n
t
t
e
m
p
e
r
a
t
u
r
e
(°C
)
O
u
t
p
u
t
Current
(
A
(
(
mps)
N
a
tural Convection
a
a
Effi ciency vs. Line Voltage and Load Current @ 25°C
Effi ciency vs. Line Voltage and Load Current @ 25°C
UEI15-033-Q12
UEI15-033-Q48
50
55
60
65
70
75
80
85
90
0 0.5 1 1.5 2 2.5 3 3.5 4
Load Current (Amps)
Efficiency (%)
Vin = 24 V
Vin = 36 V
Vin = 9 V
Vin = 18 V
50
55
60
65
70
75
80
85
90
Load Current (Amps)
Efficiency (%)
12345
Vin = 75 V
Vin = 18 V
Vin = 48 V
UEI15-033-Q48
www.murata-ps.com/support
PERFORMANCE DATA
Maximum Current Temperature Derating @Sea Level
(VIN = 24V, airfl ow is from pin 1 to pin 3)
0
0.5
1
1.5
0.33 m/s (65 LFM)
Ambient Temperature (
°
C)
Output Current (Amps)
20 25 35 45 55 65 7530 40 50 60 70 80 85
Maximum Current Temperature Derating @Sea Level
(VIN = 24V, airfl ow is from pin 1 to pin 3)
0
1
2
3
4
20 25 35 45 55 65 7530 40 50 60 70 80 85
0.33 m/s (65 LFM)
Ambient Tem
p
erature
(
°C
)
Output Current (Amps)
UEI15 Series
Isolated Wide Input Range 15-Watt DC/DC Converters
MDC_UEI15W.C11 Page 6 of 17
Effi ciency vs. Line Voltage and Load Current @ 25°C
UEI15-050-Q48
Load Current (Amps)
Efficiency (%)
100
90
80
70
60
50
40
30
20
10
0
0
0.5
1
1.5
2
2.5
3
Vin = 36 V
Vin = 75 V
Vin = 18 V
Vin = 24 V
Maximum Current Temperature Derating @Sea Level
(VIN = 24V or 48V, airfl ow is from input to output)
40 45 50 55 60 65 70 75 80 85
2.50
2.60
2.70
2.80
2.90
3.00
3.10
3.20
Ambient Temperature (°C)
Output Current (Amps)
Natural Convection
Effi ciency vs. Line Voltage and Load Current @ 25°C
UEI15-050-Q12
Load Current (Amps)
Efficiency (%)
10
20
30
40
50
60
70
80
90
100
0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3
Vin = 24 V
Vin = 36 V
Vin = 9 V
Vin = 18 V
Effi ciency vs. Line Voltage and Load Current @ 25°C
UEI15-120-Q12
Load Current (Amps)
Efficiency (%)
60
65
70
75
80
85
90
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3
Vin = 24 V
Vin = 36 V
Vin = 9 V
Vin = 18 V
www.murata-ps.com/support
PERFORMANCE DATA
Effi ciency vs. Line Voltage and Load Current @ 25°C UEI15-120-Q48 Maximum Current Temperature Derating @Sea Level
(VIN = 24V or 48V, airfl ow is from pin 2 to pin 1)
Load Current (Amps)
Efficiency (%)
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3
70
72
74
76
78
80
82
84
86
88
90
Vin = 48 V
Vin = 75 V
Vin = 18 V
Vin = 24 V
Ambient Temperature (°C)
Output Current (Amps)
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
40 45 50 55 60 65 70 75 80 85
Natural Convection
Effi ciency vs. Line Voltage and Load Current @ 25°C
Effi ciency vs. Line Voltage and Load Current @ 25°C
UEI15-150-Q12
Maximum Current Temperature Derating @Sea Level
(VIN = 12V and 24V, airfl ow is from input to output)
Maximum Current Temperature Derating @Sea Level
(VIN = 24V and 48V, airfl ow is from input to output)
Load Current (Amps)
Efficiency (%)
74
76
78
80
82
84
86
88
90
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1
Vin = 24 V
Vin = 36 V
Vin = 9 V
Load Current (Amps)
Efficiency (%)
60
65
70
75
80
85
90
95
0.07 0.18 0.28 0.38 0.49 0.59 0.69 0.80 0.90 1.00 1.10
Vin = 24 V
Vin = 48 V
Vin = 75 V
Vin = 18 V
UEI15-150-Q48
Ambient Temperature (°C)
Output Current (Amps)
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
40 45 50 55 60 65 70 75 80 85
Natural Convection
Ambient Temperature (°C)
Output Current (Amps)
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
40 45 50 55 60 65 70 75 80 85
Natural Convection
UEI15 Series
Isolated Wide Input Range 15-Watt DC/DC Converters
MDC_UEI15W.C11 Page 7 of 17
www.murata-ps.com/support
MECHANICAL SPECIFICATIONS, OPEN FRAME
0.32 MAX
8.1
0.41
.30
TYP
0.400
10.16
0.15
0.58
SIDE VIEW
MOUNTING
PLANE
.040±.002
.071 .002 SHOULDER
6X AT PINS 1-6
C
L
BOTTOM VIEW
#5
#4
#3
C
L
C
L
#6
#2
#1
RECOMMENDED
PRI-SEC BARRIER
0.400
10.16
0.400
10.16
0.100
2.54
0.200
5.08
0.800
20.32
TOP VIEW
PIN #1
1.10
27.9
0.96
24.4
END VIEW
0.475
REF
0.25
6.3
UEI15 Series
Isolated Wide Input Range 15-Watt DC/DC Converters
MDC_UEI15W.C11 Page 8 of 17
PHYSICAL CHARACTERISTICS
Pin Material Copper alloy
Pin Diameter 0.04˝ (1.016mm)
Pin Finish Gold plate
Through Hole Pin Material Copper alloy
TH Pin Plating Metal and Thickness Nickel subplate 50 μ-inches
Gold overplate 5 μ-inches
Weight 0.352 oz./10 grams
Electromagnetic Interference EN55022/CISPR22 (see note 1) (Requires
external fi lter)
Flammability Rating UL 94V-0
Safety
Certifi ed to UL/cUL 60950-1, CAN/CSA-
C22.2-60950-1, IEC/EN 60950-1, 2nd
edition
Case 75
Third Angle Projection
Dimensions are in inches (mm shown for ref. only).
Components are shown for reference only.
Tolerances (unless otherwise specified):
.XX ± 0.02 (0.5)
.XXX ± 0.010 (0.25)
Angles ± 1˚
Standard pin length is shown. Please refer to
the Ordering Guide for alternate pin lengths.
INPUT/OUTPUT CONNECTIONS
Pin Function
1 +Vin
2 -Vin
3 +Vout
4 Output Trim
5 -Vout
6 On/Off Control*
*The Remote On/Off can be provided
with either positive (P suffi x) or nega-
tive (N suffi x) logic
SECTION A-A
Depth
Pocket
9.5 [.38 in]
19.1 [.75 in]
Notes:
Material: Dow 220 antistat ethafoam1.
(Density: 34-35 kg/m3)
Dimensions: 252 x 252 x 19.1 mm2.
6 x 5 array (30 per tray)
3. All dimensions in millimeters [inches]
4. Tolerances unless otherwise specified: +1/-0
Typ
Typ
R
28.4
177.8
[9.92]
252.0
Typ
6.4
Typ
6.4
6.4
Typ 18.0
5x
Ref
38.1
22.9
190.5
Ref
252.0
[9.92]
25.4
4x 44.5
AA
19.1
Ref
252.0
Ref 252.0
Ref
9.5 deep
Ref
www.murata-ps.com/support
SHIPPING TRAYS AND BOXES, THROUGH-HOLE MOUNT
SHIPPING TRAY DIMENSIONS
UEI15 Series
Isolated Wide Input Range 15-Watt DC/DC Converters
MDC_UEI15W.C11 Page 9 of 17
Anti-static foam
Label
Label
Each tray is 6 x 5 units
(30 units per tray)
UEI modules are supplied in a 30-piece (6 x 5) shipping tray. The tray is an anti-static closed-cell polyethylene foam. Dimensions are shown below.
www.murata-ps.com/support
MECHANICAL SPECIFICATIONS, SURFACE MOUNT PACKAGE (MSL RATING 2)
0.400
10.16
0.13
REF
0.34
MAX
TOP VIEW
PIN #1
1.10
27.9
0.96
24.4
C
L
BOTTOM VIEW
#5
#4
#3
C
L
C
L
#6
#2
#1
0.400
10.16
0.400
10.16
0.800
20.32
0.100
2.54
0.100
2.54
END VIEW
.093
SIDE VIEW
MOUNTING
PLANE
.093 TYP
UEI15 Series
Isolated Wide Input Range 15-Watt DC/DC Converters
MDC_UEI15W.C11 Page 10 of 17
Third Angle Projection
Dimensions are in inches (mm shown for ref. only).
Components are shown for reference only.
Tolerances (unless otherwise specified):
.XX ± 0.02 (0.5)
.XXX ± 0.010 (0.25)
Angles ± 1˚
INPUT/OUTPUT CONNECTIONS
Pin Function
1 +Vin
2 -Vin
3 +Vout
4 Output Trim
5 -Vout
6 On/Off Control*
*The Remote On/Off can be provided
with either positive (P suffi x) or nega-
tive (N suffi x) logic
www.murata-ps.com/support
1.14
29.0
±.010.102
±0.252.60
10.16
0.400
0.400
10.16
2.54
0.100
2.54
20.32
0.800
6X
0.100
1.00
25.4 1
2
6
4
5
3
C
L
C
L
RECOMMENDED SMT PAD LAYOUT
Dimensions in inches [mm]
NOTE: The SMT package has an MSL 2 rating.
MECHANICAL SPECIFICATIONS, SURFACE MOUNT PACKAGE
SURFACE MOUNT TAPE AND REEL INFORMATION (MSL RATING 2)
UEI15 Series
Isolated Wide Input Range 15-Watt DC/DC Converters
MDC_UEI15W.C11 Page 11 of 17
0.909
23.10
32.00
1.260
2.00
0.079
0.118
3.00
13.0
R.256
DIRECTION OF FEED
5.0mm PICK &
PLACE LOCATION
PACKAGING CONFORMS TO EIA-481
CONVERTERS SHIPPING IN QUANTITIES
OF 100 PER REEL
2.20
56.0
COVER TAPE
0.365
9.27
SURFACE MOUNT TAPE AND REEL
www.murata-ps.com/support
UEI15 Series
Isolated Wide Input Range 15-Watt DC/DC Converters
MDC_UEI15W.C11 Page 12 of 17
TECHNICAL NOTES
Input Fusing
Certain applications and/or safety agencies may require fuses at the inputs of
power conversion components. Fuses should also be used when there is the
possibility of sustained input voltage reversal which is not current-limited. For
greatest safety, we recommend a fast blow fuse installed in the ungrounded
input supply line.
The installer must observe all relevant safety standards and regulations. For
safety agency approvals, install the converter in compliance with the end-user
safety standard, i.e. IEC/EN/UL 60950-1.
Input Reverse-Polarity Protection
If the input voltage polarity is reversed, an internal diode will become forward
biased and likely draw excessive current from the power source. If this source
is not current-limited or the circuit appropriately fused, it could cause perma-
nent damage to the converter.
Input Under-Voltage Shutdown and Start-Up Threshold
Under normal start-up conditions, converters will not begin to regulate properly
until the ramping-up input voltage exceeds and remains at the Start-Up
Threshold Voltage (see Specifi cations). Once operating, converters will not
turn off until the input voltage drops below the Under-Voltage Shutdown Limit.
Subsequent restart will not occur until the input voltage rises again above the
Start-Up Threshold. This built-in hysteresis prevents any unstable on/off opera-
tion at a single input voltage.
Users should be aware however of input sources near the Under-Voltage
Shutdown whose voltage decays as input current is consumed (such as capaci-
tor inputs), the converter shuts off and then restarts as the external capacitor
recharges. Such situations could oscillate. To prevent this, make sure the oper-
ating input voltage is well above the UV Shutdown voltage AT ALL TIMES.
Start-Up Time
Assuming that the output current is set at the rated maximum, the VIN to VOUT
Start-Up Time (see Specifi cations) is the time interval between the point when
the ramping input voltage crosses the Start-Up Threshold and the fully loaded
regulated output voltage enters and remains within its specifi ed accuracy band.
Actual measured times will vary with input source impedance, external input
capacitance, input voltage slew rate and fi nal value of the input voltage as it
appears at the converter.
These converters include a soft start circuit to moderate the duty cycle of its
PWM controller at power up, thereby limiting the input inrush current.
The On/Off Remote Control interval from On command to VOUT regulated
assumes that the converter already has its input voltage stabilized above the
Start-Up Threshold before the On command. The interval is measured from the
On command until the output enters and remains within its specifi ed accuracy
band. The specifi cation assumes that the output is fully loaded at maximum
rated current. Similar conditions apply to the On to VOUT regulated specifi cation
such as external load capacitance and soft start circuitry.
Input Source Impedance
These converters will operate to specifi cations without external components,
assuming that the source voltage has very low impedance and reasonable in-
put voltage regulation. Since real-world voltage sources have fi nite impedance,
performance is improved by adding external fi lter components. Sometimes only
a small ceramic capacitor is suffi cient. Since it is diffi cult to totally characterize
all applications, some experimentation may be needed. Note that external input
capacitors must accept high speed switching currents.
Because of the switching nature of DC/DC converters, the input of these
converters must be driven from a source with both low AC impedance and
adequate DC input regulation. Performance will degrade with increasing input
inductance. Excessive input inductance may inhibit operation. The DC input
regulation specifi es that the input voltage, once operating, must never degrade
below the Shut-Down Threshold under all load conditions. Be sure to use
adequate trace sizes and mount components close to the converter.
I/O Filtering, Input Ripple Current and Output Noise
All models in this converter series are tested and specifi ed for input refl ected
ripple current and output noise using designated external input/output compo-
nents, circuits and layout as shown in the fi gures below. External input capaci-
tors (Cin in the fi gure) serve primarily as energy storage elements, minimizing
line voltage variations caused by transient IR drops in the input conductors.
Users should select input capacitors for bulk capacitance (at appropriate
frequencies), low ESR and high RMS ripple current ratings. In the fi gure below,
the Cbus and Lbus components simulate a typical DC voltage bus. Your specifi c
system confi guration may require additional considerations. Please note that the
values of Cin, Lbus and Cbus will vary according to the specifi c converter model.
In critical applications, output ripple and noise (also referred to as periodic
and random deviations or PARD) may be reduced by adding fi lter elements
such as multiple external capacitors. Be sure to calculate component tempera-
ture rise from refl ected AC current dissipated inside capacitor ESR.
CIN
VIN CBUS
LBUS
CIN = 33μF, ESR < 700mΩ @ 100kHz
CBUS = 220μF, ESR < 100mΩ @ 100kHz
LBUS = 12μH
+VIN
-VIN
CURRENT
PROBE
TO
OSCILLOSCOPE
+
–
+
–
Figure 2. Measuring Input Ripple Current
Floating Outputs
Since these are isolated DC/DC converters, their outputs are “fl oating” with
respect to their input. The essential feature of such isolation is ideal ZERO
CURRENT FLOW between input and output. Real-world converters however do
exhibit tiny leakage currents between input and output (see Specifi cations).
These leakages consist of both an AC stray capacitance coupling component
www.murata-ps.com/support
UEI15 Series
Isolated Wide Input Range 15-Watt DC/DC Converters
MDC_UEI15W.C11 Page 13 of 17
and a DC leakage resistance. When using the isolation feature, do not allow
the isolation voltage to exceed specifi cations. Otherwise the converter may
be damaged. Designers will normally use the negative output (-Output) as
the ground return of the load circuit. You can however use the positive output
(+Output) as the ground return to effectively reverse the output polarity.
Minimum Output Loading Requirements
These converters employ a synchronous rectifi er design topology. Models
UEI15-033-Q12, UEI15-120-Q12, and UEI15-050-Q12 require 10% minimum
load to meet specifi cations. Operation under less than 10% load may slightly
increase regulation, ripple, and noise.
Thermal Shutdown
To prevent many over temperature problems and damage, these converters
include thermal shutdown circuitry. If environmental conditions cause the
temperature of the DC/DC’s to rise above the Operating Temperature Range
up to the shutdown temperature, an on-board electronic temperature sensor
will power down the unit. When the temperature decreases below the turn-on
threshold, the converter will automatically restart. There is a small amount of
hysteresis to prevent rapid on/off cycling.
CAUTION: If you operate too close to the thermal limits, the converter may shut
down suddenly without warning. Be sure to thoroughly test your application to
avoid unplanned thermal shutdown.
Temperature Derating Curves
The graphs in this data sheet illustrate typical operation under a variety of
conditions. The Derating curves show the maximum continuous ambient air
temperature and decreasing maximum output current which is acceptable
under increasing forced airfl ow measured in Linear Feet per Minute (“LFM”).
Note that these are AVERAGE measurements. The converter will accept brief
increases in temperature and/or current or reduced airfl ow as long as the aver-
age is not exceeded.
Note that the temperatures are of the ambient airfl ow, not the converter
itself which is obviously running at higher temperature than the outside air.
Also note that “natural convection” is defi ned as very fl ow rates which are not
using fan-forced airfl ow. Depending on the application, “natural convection” is
usually about 30-65 LFM but is not equal to still air (0 LFM).
MPS makes Characterization measurements in a closed cycle wind tunnel
with calibrated airfl ow. We use both thermocouples and an infrared camera
system to observe thermal performance. As a practical matter, it is quite diffi -
cult to insert an anemometer to precisely measure airfl ow in most applications.
Sometimes it is possible to estimate the effective airfl ow if you thoroughly un-
derstand the enclosure geometry, entry/exit orifi ce areas and the fan fl owrate
specifi cations. If in doubt, contact MPS to discuss placement and measurement
techniques of suggested temperature sensors.
CAUTION: If you routinely or accidentally exceed these Derating guidelines,
the converter may have an unplanned Over Temperature shut down. Also, these
graphs are all collected at slightly above Sea Level altitude. Be sure to reduce
the derating for higher density altitude.
Output Overvoltage Protection
This converter monitors its output voltage for an over-voltage condition using
an on-board electronic comparator. The signal is optically coupled to the pri-
mary side PWM controller. If the output exceeds OVP limits, the sensing circuit
will power down the unit, and the output voltage will decrease. After a time-out
period, the PWM will automatically attempt to restart, causing the output volt-
age to ramp up to its rated value. It is not necessary to power down and reset
the converter for the this automatic OVP-recovery restart.
If the fault condition persists and the output voltage climbs to excessive levels,
the OVP circuitry will initiate another shutdown cycle. This on/off cycling is referred
to as “hiccup” mode. It safely tests full current rated output voltage without damag-
ing the converter.
Output Fusing
The converter is extensively protected against current, voltage and temperature
extremes. However your output application circuit may need additional protec-
tion. In the extremely unlikely event of output circuit failure, excessive voltage
could be applied to your circuit. Consider using an appropriate fuse in series
with the output.
Output Current Limiting
As soon as the output current increases to approximately 125% to 150% of
its maximum rated value, the DC/DC converter will enter a current-limiting
mode. The output voltage will decrease proportionally with increases in output
current, thereby maintaining a somewhat constant power output. This is com-
monly referred to as power limiting.
Current limiting inception is defi ned as the point at which full power falls
below the rated tolerance. See the Performance/Functional Specifi cations. Note
particularly that the output current may briefl y rise above its rated value. This
enhances reliability and continued operation of your application. If the output
current is too high, the converter will enter the short circuit condition.
Output Short Circuit Condition
When a converter is in current-limit mode, the output voltage will drop as
the output current demand increases. If the output voltage drops too low, the
magnetically coupled voltage used to develop primary side voltages will also
drop, thereby shutting down the PWM controller. Following a time-out period,
the PWM will restart, causing the output voltage to begin ramping up to its ap-
propriate value. If the short-circuit condition persists, another shutdown cycle
will initiate. This on/off cycling is called “hiccup mode”. The hiccup cycling
Figure 3. Measuring Output Ripple and Noise (PARD)
C1
C1 = 1μF
C2 = 10μF
LOAD 2-3 INCHES (51-76mm) FROM MODULE
C2 R
LOAD
SCOPE
www.murata-ps.com/support
UEI15 Series
Isolated Wide Input Range 15-Watt DC/DC Converters
MDC_UEI15W.C11 Page 14 of 17
reduces the average output current, thereby preventing excessive internal
temperatures. A short circuit can be tolerated indefi nitely.
Trimming the Output Voltage
The Trim input to the converter allows the user to adjust the output voltage
over the rated trim range (please refer to the Specifi cations). In the trim equa-
tions and circuit diagrams that follow, trim adjustments use either a trimpot or
a single fi xed resistor connected between the Trim input and either the positive
or negative output terminals. (On some converters, an external user-supplied
precision DC voltage may also be used for trimming). Trimming resistors should
have a low temperature coeffi cient (±100 ppm/deg.C or less) and be mounted
close to the converter. Keep leads short. If the trim function is not used, leave
the trim unconnected. With no trim, the converter will exhibit its specifi ed
output voltage accuracy.
There are two CAUTIONs to be aware for the Trim input:
CAUTION: To avoid unplanned power down cycles, do not exceed EITHER the
maximum output voltage OR the maximum output power when setting the trim.
Be particularly careful with a trimpot. If the output voltage is excessive, the
OVP circuit may inadvertantly shut down the converter. If the maximum power
is exceeded, the converter may enter current limiting. If the power is exceeded
for an extended period, the converter may overheat and encounter overtem-
perature shut down.
Figure 4. Trim adjustments using a trimpot
LOAD
75-22
TURNS
+VOUT
TRIM
−VOUT
−VIN
ON/OFF
CONTROL
+VIN
Figure 6. Trim adjustments to increase Output Voltage using a Fixed Resistor
+VOUT
TRIM
ON/OFF
CONTROL
+VIN
LOAD
RTRIM UP
−VOUT
−VIN
Figure 5. Trim adjustments to decrease Output Voltage using a Fixed Resistor
LOAD
RTRIM DOWN
+VOUT
TRIM
ON/OFF
CONTROL
+VIN −VOUT
−VIN
VO– 5
– 2050
12775
– 2050
5– VO
5110 (Vo - 2.5)
VO– 12
– 5110
25000
– 5110
12 – VO
10000 (Vo-2.5)
UEI15-050-Q12, Q48
UEI15-120-Q12, Q48
VO– 3.3
– 2050
12775 RTDOWN (:) =RTUP (:) =
RTUP (:) =
RTUP (:) =
RTUP (:) =
RTDOWN (:) =
RTDOWN (:) =
RTDOWN (:) =
– 2050
3.3 – VO
5110 (Vo - 2.5)
UEI15-033-Q12, Q48
VO– 15 – 5110
25000
– 5110
15 – VO
10000 (Vo-2.5)
UEI15-150-Q12, Q48
Trim Up
<Connect trim
resistor between
Trim and −VOUT>
Trim Down
<Connect trim
resistor between
Trim and +VOUT>
CAUTION: Be careful of external electrical noise. The Trim input is a senstive
input to the converter’s feedback control loop. Excessive electrical noise may
cause instability or oscillation. Keep external connections short to the Trim
input. Use shielding if needed.
Trim Equations
Where Vo = Desired output voltage. Adjustment accuracy is subject to resis-
tor tolerances and factory-adjusted output accuracy. Mount trim resistor close
to converter. Use short leads.
Remote On/Off Control
On the input side, a remote On/Off Control can be ordered with either logic type.
Positive-logic models are enabled when the On/Off pin is left open or is
pulled high to +15V max. with respect to –VIN. Some models will also turn on
at lower intermediate voltages (see Specifi cations). Positive-logic devices are
www.murata-ps.com/support
UEI15 Series
Isolated Wide Input Range 15-Watt DC/DC Converters
MDC_UEI15W.C11 Page 15 of 17
disabled when the On/Off is grounded or brought to within a low voltage (see
Specifi cations) with respect to –VIN.
Negative-logic devices are on (enabled) when the On/Off is grounded or
brought to within a low voltage (see Specifi cations) with respect to –VIN. The
device is off (disabled) when the On/Off is left open or is pulled high to +15VDC
max. with respect to –VIN.
Dynamic control of the On/Off function should be able to sink appropriate
signal current when brought low and withstand appropriate voltage when
brought high. Be aware too that there is a fi nite time in milliseconds (see
Specifi cations) between the time of On/Off Control activation and stable,
regulated output. This time will vary slightly with output load type and current
and input conditions.
There are three CAUTIONs for the On/Off Control:
CAUTION: To retain full output circuit isolation, control the On/Off from the in-
put side ONLY. If you must control it from circuits in the output, use some form
of optoisolation to the On/Off Control. This latter condition is unlikely because
the device controlling the On/Off would have to remain powered on and not be
powered from the converter.
CAUTION: While it is possible to control the On/Off with external logic if you
carefully observe the voltage levels, the preferred circuit is either an open
drain/open collector transistor, a switch or a relay (which can thereupon be
controlled by logic).
CAUTION: Do not apply voltages to the On/Off pin when there is no input
power voltage. Otherwise the converter may be permanently damaged.
Figure 7. Driving the On/Off Control Pin (suggested circuit)
ON/OFF CONTROL
CONTROL
+ Vcc
-VIN
Through-hole Soldering Guidelines
Murata Power Solutions recommends the TH soldering specifi cations below when install-
ing these converters. These specifi cations vary depending on the solder type. Exceeding
these specifi cations may cause damage to the product. Your production environment may
differ; therefore please thoroughly review these guidelines with your process engineers.
Wave Solder Operations for through-hole mounted products (THMT)
For Sn/Ag/Cu based solders:
Maximum Preheat Temperature 115° C.
Maximum Pot Temperature 270° C.
Maximum Solder Dwell Time 7 seconds
For Sn/Pb based solders:
Maximum Preheat Temperature 105° C.
Maximum Pot Temperature 250° C.
Maximum Solder Dwell Time 6 seconds
SMT Refl ow Soldering Guidelines
The surface-mount refl ow solder profi le shown below is suitable for SAC305 type lead-
free solders. This graph should be used only as a guideline. Many other factors infl uence
the success of SMT refl ow soldering. Since your production environment may differ,
please thoroughly review these guidelines with your process engineers.
www.murata-ps.com/support
UEI15 Series
Isolated Wide Input Range 15-Watt DC/DC Converters
MDC_UEI15W.C11 Page 16 of 17
Emissions Performance
Murata Power Solutions measures its products for radio frequency emissions
against the EN 55022 and CISPR 22 standards. Passive resistance loads are
employed and the output is set to the maximum voltage. If you set up your
own emissions testing, make sure the output load is rated at continuous power
while doing the tests.
The recommended external input and output capacitors (if required) are
included. Please refer to the fundamental switching frequency. All of this
information is listed in the Product Specifi cations. An external discrete fi lter is
installed and the circuit diagram is shown below.
[1] Conducted Emissions Parts List
[2] Conducted Emissions Test Equipment Used
Rohde & Schwarz EMI Test Receiver (9KHz – 1000MHz) ESPC
Rohde & Schwarz Software ESPC-1 Ver. 2.20
HP11947A Transient Limiter (Agilent)
OHMITE 25W – Resistor combinations
DC Source Power Supply – Kikisui Model PAD 55-6L
[3] Conducted Emissions Test Results
[4] Layout Recommendations
Most applications can use the fi ltering which is already installed inside the
converter or with the addition of the recommended external capacitors. For
greater emissions suppression, consider additional fi lter components and/or
shielding. Emissions performance will depend on the user’s PC board layout,
the chassis shielding environment and choice of external components. Please
refer to Application Note GEAN02 for further discussion.
Since many factors affect both the amplitude and spectra of emissions, we
recommend using an engineer who is experienced at emissions suppression.
Reference Part Number Description Vendor
L2 PE-62913 1mH, 6A Pulse
L1 500uH,10A, MPS 500uH,10A Murata
C1 Ceramic 2.2ufd, 100V Murata
C2 Electrolytic Capacitor 33ufd, 100V Panasonic
Graph 1. Conducted emissions performance,
CISPR/EN55022, Class B, full load, fi ltered
Graph 1. Conducted emissions performance,
CISPR/EN55022, Class B, full load, unfi ltered
Figure 8. Conducted Emissions Test Circuit
UEI15-050-Q12P-C EMI 15W Test Card
24Vdc in, 5Vout, 3Amps
V+
V-
Black
Vin - Vout -
Vout +Vin +
Resistive
Load
UUT
L2
L1
C1C1C1C1 C1C1 C2C1C1C1
Resistive
Load
inside a
metal
container
www.murata-ps.com/support
Murata Power Solutions, Inc. makes no representation that the use of its products in the circuits described herein, or the use of other
technical information contained herein, will not infringe upon existing or future patent rights. The descriptions contained herein do not imply
the granting of licenses to make, use, or sell equipment constructed in accordance therewith. Specifi cations are subject to change without
notice. © 2013 Murata Power Solutions, Inc.
Murata Power Solutions, Inc.
11 Cabot Boulevard, Mansfi eld, MA 02048-1151 U.S.A.
ISO 9001 and 14001 REGISTERED
This product is subject to the following operating requirements
and the Life and Safety Critical Application Sales Policy:
Refer to: http://www.murata-ps.com/requirements/
UEI15 Series
Isolated Wide Input Range 15-Watt DC/DC Converters
MDC_UEI15W.C11 Page 17 of 17
Figure 9. Vertical Wind Tunnel
IR Video
Camera
IR Transparent
optical window Variable
speed fan
Heating
element
Ambient
temperature
sensor
Airflow
collimator
Precision
low-rate
anemometer
3” below UUT
Unit under
test (UUT)
Vertical Wind Tunnel
Murata Power Solutions employs a computer controlled
custom-designed closed loop vertical wind tunnel, infrared video
camera system, and test instrumentation for accurate airfl ow and
heat dissipation analysis of power products. The system includes
a precision low fl ow-rate anemometer, variable speed fan, power
supply input and load controls, temperature gauges, and adjust-
able heating element.
The IR camera monitors the thermal performance of the Unit
Under Test (UUT) under static steady-state conditions. A special
optical port is used which is transparent to infrared wavelengths.
Both through-hole and surface mount converters are soldered
down to a host carrier board for realistic heat absorption and
spreading. Both longitudinal and transverse airfl ow studies are
possible by rotation of this carrier board since there are often
signifi cant differences in the heat dissipation in the two airfl ow
directions. The combination of adjustable airfl ow, adjustable
ambient heat, and adjustable Input/Output currents and voltages
mean that a very wide range of measurement conditions can be
studied.
The collimator reduces the amount of turbulence adjacent
to the UUT by minimizing airfl ow turbulence. Such turbulence
infl uences the effective heat transfer characteristics and gives
false readings. Excess turbulence removes more heat from some
surfaces and less heat from others, possibly causing uneven
overheating.
Both sides of the UUT are studied since there are different thermal
gradients on each side. The adjustable heating element and fan, built-in
temperature gauges, and no-contact IR camera mean that power supplies
are tested in real-world conditions.
