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UHE Series
Isolated, High Eficiency, 1.6" × 2"
2-10 Amp, 12-30 Watt DC/DC Converters
Housed in smaller, 1.6" x 2" x 0.40" (41 x 51 x 10.2mm)
packages carrying the standard 2" x 2" pinout, MPS’s new
UHE Series DC/DC Converters deliver more current/power
(up to 10A/30W) than currently available from either
package size.
Typical units
FEATURES
n
The most I
OUT
/P
OUT
in this format
n
Lower priced than bricks
n
Small 1.6" x 2" x 0.4" plastic package
with standard 2" x 2" pinout
n
Output conigurations:
1.2/1.5/1.8/2.5V
OUT
@ 10 Amps
3.3/5V
OUT
@ 25 Watts
5/12/15V
OUT
@ 30 Watts
n
Five input ranges from 9-75 Volts
n
Eficiencies as high as 91.5%
n
Stable no-load operation
n
Optional Sense pins for low V
OUT
n
Thermal shutdown, I/O protected
n
1500 Vdc I/O BASIC Insulation
n
UL/EN60950-1 certiied;
CE marked for Q48 models
n
RoHS compliant
PRODUCT OVERVIEW
The UHE 12-30W Series of high-eficiency,
isolated DC/DC’s provide output power ranging
from 10 Amps @ 1.2V to 2 Amps @ 15V. Offering
both 2:1 and 4:1 input voltage ranges, UHE’s meet
V
i n
requirements from 9 to 75 Volts.
Taking full advantage of the synchronous-
rectiier, forward topology, UHEs boast outstanding
eficiency (some models exceed 91%) enabling
full-power operation to ambient temperatures as
high as +60°C, without air low. Assembled using
fully automated, SMT-on-pcb techniques, UHEs
provide stable no-load operation, excellent line
(±0.1%) and load (±0.15%) regulation, quick step
response (200µsec), and low output ripple/noise
(50-100mVp-p). Additionally, the UHEs unique
output design eliminates one of the topology’s few
shortcomings–output reverse conduction.
All devices feature full I/O fault protection
including: input overvoltage and undervoltage
shutdown, precise output overvoltage protection
(a rarity on low-voltage outputs), output current
limiting, short-circuit protection, and thermal
shutdown.
All UHE models incorporate a V
o u t
Trim function
and an On/Off Control pin (positive or negative
polarity). Low-voltage models (1.2V to 5V) offer
optional sense pins facilitating either remote
load regulation or current sharing for true N+1
redundancy. All models are certiied to the BASIC
insulation requirements of UL/EN60950-1, and
48V
i n
(75V max.) models carry the CE mark.
Selected models are RoHS compliant (Reduction
of Hazardous Substances).
SIMPLIFIED SCHEMATIC
+INPUT
(1)
+OUTPUT
(6)
SWITCH
CONTROL
+SENSE
(5)
–OUTPUT
(7)
–SENSE
(8)
OPTO
ISOLATION
THERMAL
SHUTDOWN
–INPUT
(2)
OVERVOLTAGE
COMPARATOR
Ḥ
PWM
CONTROLLER
OPTO
ISOLATION
REFERENCE &
ERROR AMP
V
OUT
TRIM
(9)
For full details go to
www.murata-ps.com/rohs
UVLO & OVLO
COMPARATORS
ON/OFF
CONTROL
(4)
Typical topography is shown.

Optional comparator feedback. Contact MPS.

Sense pins are optional on 1.2-5V
OUT
models ("R" sufix).
*
One phase of two is shown.
Figure 1. Simpliied Schematic
www.murata-ps.com
Technical enquiries email: sales@murata-ps.com, tel: +1 508 339 3000
MDC_UHE Series.B08 Page 1 of 14
 UHE Series
Isolated, High Eficiency, 1.6" × 2"
2-10 Amp, 12-30 Watt DC/DC Converters
PERFORMANCE SPECIFICATIONS AND ORDERING GUIDE
➀
Model Family
(See model numbering
on page 13)
Output
Input
Package
(Case/
Pinout)
Regula
t
ion (Max.)
Eficiency
V
OUT
(Volts)
I
OUT
(Amps)
R/N (mVp-p)➁
V
IN
Nom.
(Volts)
Range
(Volts)
I
i n
➂
(mA/A)
Typ.
Max.
Line
Load
➃
Min.
Typ.
UHE-1.2/10000-D12 ➄ 1.2
10
80
120
±0.1%
±0.15/0.625%
12
9-18
35/1.27
80%
82%
C32, P51/52
UHE-1.2/10000-D24 ➄
1.2
10
80
120
±0.1%
±0.15/0.625%
24
18-36
35/0.63
81%
83%
C32, P51/52
UHE-1.2/10000-D48
1.2
10
80
120
±0.1%
±0.15/0.625%
48
36-75
35/0.31
81%
83%
C32, P51/52
UHE-1.5/10000-D12
1.5
10
55
80
±0.1%
±0.15/0.625%
12
9-18
35/1.56
81%
83%
C32, P51/52
UHE-1.5/10000-D24
1.5
10
55
80
±0.1%
±0.15/0.625%
24
18-36
35/0.76
84%
86%
C32, P51/52
UHE-1.5/10000-D48
1.5
10
55
80
±0.1%
±0.15/0.625%
48
36-75
35/0.38
82%
84%
C32, P51/52
UHE-1.8/10000-D12
➄
1.8
10
55
80
±0.1%
±0.15/0.625%
12
9-18
35/1.81
84%
85.5%
C32, P51/52
UHE-1.8/10000-D24
1.8
10
70
90
±0.1%
±0.15/0.625%
24
18-36
35/0.89
85.5%
87%
C32, P51/52
UHE-1.8/10000-D48
1.8
10
50
75
±0.1%
±0.15/0.625%
48
36-75
35/0.46
83.5%
85%
C32, P51/52
UHE-2.5/10000-D12
2.5
10
50
75
±0.1%
±0.15/0.5%
12
9-18
35/2.48
85%
87%
C32, P51/52
UHE-2.5/10000-D24
2.5
10
50
75
±0.1%
±0.15/0.5%
24
18-36
35/1.23
86%
88%
C32, P51/52
UHE-2.5/10000-D48
2.5
10
50
75
±0.1%
±0.15/0.5%
48
36-75
35/0.61
86%
88%
C32, P51/52
UHE-3.3/7500-Q12
3.3
7.5
50
70
±0.1%
±0.2/0.5%
24
9-36
50/1.2
86.5%
88%
C32, P51/52
UHE-3.3/7500-Q48
3.3
7.5
60
90
±0.1%
±0.15/0.3%
48
18-75
38/0.6
87.5%
89.5%
C32, P51/52
UHE-3.3/7500-D48
3.3
7.5
60
90
±0.1%
±0.15/0.3%
48
36-75
35/0.6
88.5%
91%
C32, P51/52
UHE-3.3/7500-D48T
3.3
7.5
80
100
±0.1%
±0.25%
48
36-75
35/0.58
87%
88.5%
C32, P51
UHE-5/5000-Q12
5
5
50
70
±0.1%
±0.15/0.3%
24
9-36
50/1.22
86%
87.5%
C32, P51/52
UHE-5/5000-Q48
5
5
60
90
±0.05%
±0.15/0.3%
48
18-75
35/0.6
87.5%
90%
C32, P51/52
UHE-5/6000-Q12
5
6
50
70
±0.075%
±0.15%
24
9-36
50/1.44
86.5%
87%
C32, P51/52
UHE-5/6000-D48
5
6
80
100
±0.1%
±0.25/0.5%
48
36-75
45/0.73
87.5%
89%
C32, P51/52
UHE-5/6000-D48T
5
6
80
100
±0.1%
±0.25%
48
36-75
45/0.7
87.5%
89%
C32, P51
UHE-5/6000-Q48T
5
6
90
125
±0.1%
±0.45%
48
18-75
38/0.71
86%
87.5%
C32, P51
UHE-12/2500-Q12
12
2.5
100
120
±0.1%
±0.3%
24
9-36
145/1.5
85%
87.5%
C32, P51
UHE-12/2500-D12
12
2.5
65
100
±0.1%
±0.3%
12
9-18
90/2.92
87%
89%
C32, P51
UHE-12/2500-D24
12
2.5
65
100
±0.1%
±0.3%
24
18-36
55/1.44
88%
90%
C32, P51
UHE-12/2500-Q48
12
2.5
100
120
±0.1%
±0.3%
48
18-75
45/0.72
88%
90.5%
C32, P51
UHE-12/2500-D48
12
2.5
60
100
±0.1%
±0.3%
48
36-75
30/0.7
90%
92%
C32, P51
UHE-15/2000-D12
15
2
70
100
±0.1%
±0.3%
12
9-18
110/2.92
87%
89%
C32, P51
UHE-15/2000-Q12
15
2
70
100
±0.1%
±0.5%
24
9-36
50/1.42
86%
88%
C32, P51
UHE-15/2000-D24
15
2
70
100
±0.1%
±0.3%
24
18-36
70/1.44
88%
90%
C32, P51
UHE-15/2000-Q48
15
2
100
150
±0.1%
±0.3%
48
18-75
45/0.72
88%
90.5%
C32, P51
UHE-15/2000-D48
15
2
70
100
±0.1%
±0.3%
48
36-75
35/0.7
90%
92%
C32, P51

Typical at T
A
= +25°C under nominal line voltage and full-load conditions, unless noted.

Ripple/Noise (R/N) is tested/speciied over a 20MHz bandwidth. All models are speciied with
an external 0.47µF multi-layer ceramic capacitor installed across their output pins.

Nominal line voltage, no-load/full-load conditions.

Devices have no minimum-load requirements and will regulate under no-load conditions.
Regulation speciications describe the output voltage deviation as the line voltage or load
(with/without sense option) is varied from its nominal/midpoint value to either extreme.

Contact Murata Power Solutions for availability.
MECHANICAL SPECIFICATIONS
2.00
(50.80)
INPUT/OUTPUT CONNECTIONS
Pin
PLASTIC CASE
Function P51
Function P52
0.40
(10.16)
1
+Input
+Input
2
–Input
–Input
STANDOFF
0.020 (0.51)
3
No Pin
No Pin
0.040 ±0.001 DIA.
(1.016 ±0.025)
0.20 MIN
(5.08)
4
On/Off Control
On/Off Control
5
No Pin
Sense*
1.800
(45.72)
0.10
(2.54)
6
+Output
+Output
7
–Output
–Output
0.200
(5.08)
0.200
(5.08)
8
No Pin
–Sense*
5
9
Trim
Trim
6
1
2
1.60
(40.64)
* Pins 5 and 8 are installed for optional R-sufix versions of 1.2-5V
OUT
models.
0.400
(10.16)
7
0.400
(10.16)
3
0.400 (10.16)
2 EQ. SP. @
0.200 (5.08)
See page 13 for complete Part Number structure & ordering details.
8
4
9
0.100
(2.54)
BOTTOM VIEW
0.20
(5.08)
DIMENSIONS ARE IN INCHES (MM)
www.murata-ps.com
Technical enquiries email: sales@murata-ps.com, tel: +1 508 339 3000
MDC_UHE Series.B08 Page 2 of 14
 UHE Series
Isolated, High Eficiency, 1.6" × 2"
2-10 Amp, 12-30 Watt DC/DC Converters
Performance/Functional Speciications
Typical @ T
A
= +25°C under nominal line voltage and full-load conditions, unless noted. ➀ ➁
Input
Output
Input Voltage Range:
Overvoltage Protection:
Magnetic feedback
D12 Models (start up at 10V max.)
9-18 Volts (12V nominal)
1.2V Outputs
1.5-2.1 Volts
Q12 Models (start up at 10V max.)
9-36 Volts (24V nominal)
1.5V Outputs
1.8-2.4 Volts
D24 Models
18-36 Volts (24V nominal)
1.8V Outputs
2.2-2.8 Volts
Q48 Models
18-75 Volts (48V nominal)
2.5V Outputs
2.8 to 3.2 Volts
D48 Models
36-75 Volts (48V nominal)
3.3V Outputs
4 to 4.8 Volts
5V Outputs
6.1-7.5 Volts
Overvoltage Shutdown:
12V
Outputs
12.7-13.5 Volts
D12 Models
18.5-23 Volts
15V
Outputs
15.8-16.2 Volts
Q12/D24 Models
37-42 Volts
D48/Q48 Models
Not applicable
Maximum Capacitive Loading:
10,000µF (1.2-5V
OUT
)
(Low ESR capacitor)
2,000µF (12-15V
OUT
)
Dynamic Characteristics
Start-Up Threshold:
➁
D12/Q12 Models
9.4-10 Volts
D24/Q48 Models
15.5-18 Volts
Dynamic Load Response:
D48 Models
33.5-36 Volts
(50-100% load step to ±3% V
OUT
)
200µsec maximum
➇
Undervoltage Shutdown:
➁
Start-Up Time:
➇
8msec typical
D12/Q12 Models
7.0-8.8 Volts
V
IN
to V
OUT
and On/Off
to V
OUT
15msec maximum
D24/Q48 Models
15-17 Volts
UHE-15/2000-Q12
30mS typ., 50mS max.
D48 Models
32-35.5 Volts
Switching Frequency
150-350kHz (model dependent)
Environmental
Input Current:
Normal Operating Conditions
See Ordering Guide
Standby Mode (Off, OV, UV)
5mA
MTBF
➈
TBC million hours
Input Relected Ripple Current
➂
10mAp-p
Operating Temperature (Ambient):
➉
Input Filter Type
LC or Pi type
Without Derating
–40 to +65°C (model dependent)
Reverse-Polarity Protection
Brief duration, 5A maximum
With Derating
To +100°C (see Derating Curves)
Thermal Shutdown
+115°C to +130°C
Remote On/Off Control (Pin 4):
➃
Positive Logic (Standard)
On = open, open collector, or
Storage Temperature
–55 to +125°C
+13V to V
IN
applied. I
IN
= 2.6mA max.
Flammability
94V
Physical
Off = pulled low to 0-0.8V. I
IN
= 2mA max.
Negative Logic ("N" Sufix Models)
On = pulled low to 0-0.8V. I
IN
= 6mA max.
Off = open, open collector or
Dimensions
1.6" x 2" x 0.40" (40.64 x 50.8 x 10.16mm)
+3.5V to V
IN
applied. I
IN
= 1mA max.
Output
Case Material
Diallyl Phthalate
Pin Material
Gold-plated copper alloy
Weight
1.51 ounces (46.9 grams)
V
OUT
Accuracy (50% load):
Initial ±1.5%
Temperatue Coeficient ±0.02% per °C
Extreme
(5)
±3%
Minimum Loading for Speciication:
➁
No load
Ripple/Noise (20MHz BW)
➀
Primary to Secondary Insulation Level
Basic
➀ All models are tested and speciied with a single, external, 0.47µF, multi-layer ceramic output
capacitor and no external input capacitors, unless otherwise noted. All models will effectively
regulate under no-load conditions (with perhaps a slight increase in output ripple/noise).
➁ See Technical Notes/Performance Curves for additional explanations and details.
➂ Input Ripple Current is tested/speciied over a 5-20MHz bandwidth with an external 33µF input
capacitor and a simulated source impedance of 220µF and 12µH. See I/O Filtering, Input Ripple
Current and Output Noise for details.
➃ The On/Off Control is designed to be driven with open-collector (or equivalent) logic or the applica-
tion of appropriate voltages (referenced to –Input (pin 2)). Applying a voltage to the On/Off Control
pin when no input voltage is applied to the converter can cause permanent damage. See Remote
On/Off Control for more details.
➄ Extreme Accuracy refers to the accuracy of either trimmed or untrimmed output voltages over all
normal operating ranges and combinations of input voltage, output load and temperature.
➅ Tie the Output Trim pin (pin 9) to +Output (pin 6) for maximum trim down or to –Output (Output
Return/Common, pin 7) for maximum trim up. See Output Trimming for detailed trim equations.
➆ The Current-Limit-Inception point is the output current level at which the converter's power-limiting
circuitry drops the output voltage 2% from its initial value. See Output Current Limiting and
Short-Circuit Protection for more details.
➇ For Start-Up-Time speciications, output settling time is deined as the output voltage having
reached ±1% of its inal value at maximum load current.
➈ MTBF’s are calculated using TELCORDIA SR-332 Method 1 Case, ground ixed, +25°C ambient air
and full-load conditions. Contact MPS for demonstrated life-test data.
➉ All models are fully operational and meet all published speciications, including "cold start," at –40°C.
See Ordering Guide
Line/Load Regulation
See Ordering Guide
Eficiency
See Ordering Guide
V
OUT
Trim Range
(6)
±5% minimum (±10% for T models)
Remote Sense Compensation
➁
±5%
Isolation Voltage:
Input-to-Output
1500Vdc minimum (BASIC)
Isolation Capacitance
650pF
Isolation Resistance
100M
Ω
Current Limit Inception (@98%V
OUT
):
➆
10 Amp Models
12-15 Amps
7.5 Amp Models
8.2-11.5 Amps
5/6 Amp Models
6.5-8.5 Amps
2.5 Amp Models
2.6-4 Amps
2.0 Amp Models
2.1-3 Amps
Short Circuit Current (Hiccup)
1.5-2.3 Amps
www.murata-ps.com
Technical enquiries email: sales@murata-ps.com, tel: +1 508 339 3000
MDC_UHE Series.B08 Page 3 of 14
 UHE Series
Isolated, High Eficiency, 1.6" × 2"
2-10 Amp, 12-30 Watt DC/DC Converters
Input Undervoltage Shutdown and Start-Up Threshold
Under normal start-up conditions, devices will not begin to regulate until
the ramping-up input voltage exceeds the Start-Up Threshold Voltage. Once
operating, devices will not turn off until the input voltage drops below the
Undervoltage Shutdown limit. Subsequent re-start will not occur until the input
is brought back up to the Start-Up Threshold. This built in hysteresis prevents
any unstable on/off situations from occurring at a single input voltage.
Absolute Maximum Ratings
Input Voltage:
Continuous:
D12 Models
23 Volts
D24/Q12 Models
42 Volts
D48/Q48 Models
81 Volts
Transient (100msec):
D12 Models
25 Volts
D24/Q12 Models
50 Volts
Start-Up Time
The V
i n
to V
o u t
Start-Up Time is the interval of time between the point at which
the ramping input voltage crosses the Start-Up Threshold and the fully loaded
output voltage enters and remains within its speciied accuracy band. Actual
measured times will vary with input source impedance, external input/output
capacitance, and load. The UHE Series implements a soft start circuit that limits
the duty cycle of its PWM controller at power up, thereby limiting the input
inrush current.
D48/Q48 Models
100 Volts
On/Off Control (pin 4) Max. Voltages
Referenced to –Input (pin 2)
No Sufix
+V
IN
"N" Sufix
+7 Volts
Input Reverse-Polarity Protection
Current must be <5 Amps. Brief
duration only. Fusing recommended.
Output Current
Current limited. Devices can
withstand sustained output short
The On/Off Control to V
o u t
start-up time assumes the converter has its
nominal input voltage applied but is turned off via the On/Off Control pin. The
speciication deines the interval between the point at which the converter is
turned on and the fully loaded output voltage enters and remains within its
speciied accuracy band. Similar to the V
i n
to V
o u t
start-up, the On/Off Control
to V
o u t
start-up time is also governed by the internal soft start circuitry and
external load capacitance.
circuits without damage.
Case Temperature
+100°C
Storage Temperature
–55 to +125°C
Lead Temperature (soldering, 10 sec.)
+300°C
These are stress ratings. Exposure of devices to any of these conditions may adversely
affect long-term reliability. Proper operation under conditions other than those listed in
the Performance/Functional Speciications Table is not implied.
The difference in start up time from V
i n
to V
o u t
and from On/Off Control to
V
o u t
is therefore insigniicant.
Input Overvoltage Shutdown
All D12/Q12 and D24 Models of the UHE DC/DC converters are equipped with
Input Overvoltage Protection. Input voltages exceeding the input overvoltage
shutdown speciication listed in the Performance/Functional Speciications will
cause the device to shutdown. A built-in hysteresis for all models will not allow
the converter to restart until the input voltage is suficiently reduced.
TECHNICAL NOTES
Input Fusing
Certain applications and/or safety agencies may require the installation of
fuses at the inputs of power conversion components. Fuses should also be
used if the possibility of sustained, non-current-limited, input-voltage polarity
reversals exists. For MPS’s UHE 12-30 Watt DC/DC Converters, you should use
slow-blow type fuses, installed in the ungrounded input supply line, with values
no greater than the following.
Model Fuse Values in Amps
Output/Input D12 Q12 D24 Q48 D48
1.2 V
o u t
3 -- 2 -- 1
1.5 V
o u t
4 -- 2 -- 1
1.8 V
o u t
5 -- 2.5 -- 1
2.5 V
o u t
5 -- 2.5 -- 1
3.3 V
o u t
-- 7.5 - 3 1.5
5 V
o u t
-- 5 - 3 2
12 V
o u t
6 3 3 5 2
15 V
o u t
6 3 3 5 2
All relevant national and international safety standards and regulations must be
observed by the installer. For system safety agency approvals, the converters
must be installed in compliance with the requirements of the end-use safety
standard, e.g. IEC/EN/UL60950-1.
All 48V
i n
models have this overvoltage shutdown function disabled because
of requirements for withstanding brief input surges to 100V for up to 100µsec
without output voltage interruption.
Please contact MPS to have input overvoltage shutdown for D48/Q48
models enabled.
Input Source Impedance
UHE converters must be driven from a low ac-impedance input source. The
DC/DC's performance and stability can be compromised by the use of highly
inductive source impedances. The input circuit shown in Figure 2 is a practical
solution that can be used to minimize the effects of inductance in the input
traces. For optimum performance, components should be mounted close to
the DC/DC converter. If the application has a high source impedance, low V
IN
models can beneit of increased external input capacitance.
I/O Filtering, Input Ripple Current, and Output Noise
All models in the UHE 12-30 Watt DC/DC Converters are tested/speciied for in-
put relected ripple current and output noise using the speciied external input/
output components/circuits and layout as shown in the following two igures.
External input capacitors (C
IN
in Figure 2) serve primarily as energy-storage
elements, minimizing line voltage variations caused by transient IR drops
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Technical enquiries email: sales@murata-ps.com, tel: +1 508 339 3000
MDC_UHE Series.B08 Page 4 of 14
 UHE Series
Isolated, High Eficiency, 1.6" × 2"
2-10 Amp, 12-30 Watt DC/DC Converters
in conductors from backplane to the DC/DC. Input caps should be selected
for bulk capacitance (at appropriate frequencies), low ESR, and high rms-
ripple-current ratings. The switching nature of DC/DC converters requires that
dc voltage sources have low ac impedance as highly inductive source imped-
ance can affect system stability. In Figure 2, C
BUS
and L
BUS
simulate a typical
dc voltage bus. Your speciic system coniguration may necessitate additional
considerations.
Floating Outputs
Since these are isolated DC/DC converters, their outputs are "loating" with
respect to their input. Designers will normally use the –Output (pin 7) as the
ground/return of the load circuit. You can, however, use the +Output (pin 6) as
ground/return to effectively reverse the output polarity.
Minimum Output Loading Requirements
UHE converters employ a synchronous-rectiier design topology and all models
regulate within spec and are stable under no-load to full load conditions.
Operation under no-load conditions however might slightly increase the output
ripple and noise.
TO
OSCILLOSCOPE
CURRENT
PROBE
+INPUT
L
BUS
+
Thermal Shutdown
These UHE converters are equipped with thermal-shutdown circuitry. If envi-
ronmental conditions cause the internal temperature of the DC/DC converter to
rise above the designed operating temperature, a precision temperature sensor
will power down the unit. When the internal temperature decreases below the
threshold of the temperature sensor, the unit will self start. See Performance/
Functional Speciications.
V
IN
C
BUS
C
IN
–
–INPUT
C
IN
= 33µF, ESR < 700m
7
@ 100kHz
C
BUS
= 220µF, ESR < 100m
7
@ 100kHz
L
BUS
= 12µH
Figure 2. Measuring Input Ripple Current
Output Overvoltage Protection
UHE output voltages are monitored for an overvoltage condition via magnetic
feedback. The signal is coupled to the primary side and if the output voltage
rises to a level which could be damaging to the load, the sensing circuitry will
power down the PWM controller causing the output voltages to decrease. Fol-
lowing a time-out period the PWM will restart, causing the output voltages to
ramp to their appropriate values. If the fault condition persists, and the output
voltages again climb to excessive levels, the overvoltage circuitry will initiate
another shutdown cycle. This on/off cycling is referred to as "hiccup" mode.
In critical applications, output ripple/noise (also referred to as periodic and
random deviations or PARD) may be reduced below speciied limits using ilter-
ing techniques, the simplest of which is the installation of additional external
output capacitors. These output caps function as true ilter elements and
should be selected for bulk capacitance, low ESR and appropriate frequency
response. All external capacitors should have appropriate voltage ratings and
be located as close to the converter as possible. Temperature variations for all
relevant parameters should also be taken carefully into consideration.
Contact MPS for an optional output overvoltage monitor circuit using a
comparator which is optically coupled to the primary side thus allowing tighter
and more precise control.
The most effective combination of external I/O capacitors will be a function
of line voltage and source impedance, as well as particular load and layout
conditions. Our Applications Engineers can recommend potential solutions and
discuss the possibility of our modifying a given device's internal iltering to
meet your speciic requirements. Contact our Applications Engineering Group
for additional details.
Current Limiting
As soon as the output current increases to 10% to 50% above its rated value,
the DC/DC converter will go into a current-limiting mode. In this condition, the
output voltage will decrease proportionately with increases in output current,
thereby maintaining somewhat constant power dissipation. This is commonly
referred to as power limiting. Current limit inception is deined as the point at
which the full-power output voltage falls below the speciied tolerance. See
Performance/Functional Speciications. If the load current, being drawn from
the converter, is signiicant enough, the unit will go into a short circuit condition
as speciied under “Performance.”
COPPER STRIP
+SENSE
+OUTPUT
R
LOAD
SCOPE
C1
C2
–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 voltages to begin ramping to their
appropriate values. If the short-circuit condition persists, another shutdown
cycle will be initiated. This on/off cycling is referred to as “hiccup” mode. The
hiccup cycling reduces the average output current, thereby preventing internal
temperatures from rising to excessive levels. The UHE is capable of enduring
an indeinite short circuit output condition.
COPPER STRIP
–SENSE
C1 = 0.47µF CERAMIC
C2 = NA
LOAD 2-3 INCHES (51-76mm) FROM MODULE
Figure 3. Measuring Output Ripple/Noise (PARD)
In Figure 3, the two copper strips simulate real-world pcb impedances
between the power supply and its load. In order to minimize measurement errors,
scope measurements should be made using BNC connectors, or the probe
ground should be less than ½ inch and soldered directly to the ixture.
www.murata-ps.com
Technical enquiries email: sales@murata-ps.com, tel: +1 508 339 3000
MDC_UHE Series.B08 Page 5 of 14
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