MURATA OKY-T-3, OKY-T-5 Technical data
www.murata-ps.com
Typical unit
FEATURES
■ Non-isolated SMT POL DC/DC power module
■ 8.3-14Vdc input voltage range
■ Programmable output voltage from 0.75-5.5Vdc
■ 3 Amp (T/3) or 5 Amp (T/5) output current models
■ Drives 1000 µF capacitive loads
■ High power conversion effi ciency 93% at 3.3 Vout
■ Outstanding thermal derating performance
■ Over temperature and over current protection
■ On/Off control
■ UL/EN/IEC 60950-1 safety
■ Industry-standard (DOSA) surface-mount package
■ RoHS6 hazardous substance compliance
OKY-T/3,T/5-D12 Series
Adjustable Output 3 and 5-Amp DOSA-SMT DC/DC Converters
PRODUCT OVERVIEW
The OKY-T/3 and -T/5 series are miniature nonisolated Point-of-Load (POL) switch mode DC/DC
power converters for embedded applications. The
module is fully compatible with Distributed-power
Open Standards Alliance (DOSA) industry-standard
specifi cations (www.dosapower.com). Applications
include powering CPU’s, datacom/telecom systems,
distributed bus architectures (DBA), programmable
logic and mixed voltage systems.
The wide input range is 8.3 to 14 Volts DC. Two
maximum output currents are offered, 3 Amps (T/3
models) or 5 Amps (T/5 models). Based on fi xed-
Contents Page
Description, Connection Diagram, Photograph 1
Ordering Guide, Model Numbering 2
Mechanical Specifi cations, Input/Output Pinout 3
Detailed Electrical Specifi cations 4
Output Voltage Adjustment, Soldering Guidelines 5
Application Notes 6
OKY-T/3-D12 Performance Data and Oscillograms 9
OKY-T/5-D12 Performance Data and Oscillograms 15
Tape and Reel Information 21
frequency synchronous buck converter switching
topology, the high power conversion effi cient Point
of Load (POL) module features programmable
output voltage and On/Off control. These converters
also include under voltage lock out (UVLO), output
short circuit protection, over-current and over
temperature protections.
These units are designed to meet all standard
UL/EN/IEC 60950-1 safety and FCC EMI/RFI
emissions certifi cations and RoHS6 hazardous
substance compliance.
F1
External
DC
Power
Source
For full details go to
www.murata-ps.com/rohs
+Vin +Vout
Connection Diagram
On/Off
Control
Open = On
Closed = Off
Controller
Note: Murata Power Solutions strongly recommends an external input fuse, F1.
See specifi cations.
www.murata-ps.com
t4XJUDIJOH
t'JMUFST
t$VSSFOU4FOTF
Reference and
Error Amplifier
CommonCommon
Figure 1. OKY-T/3, -T/5
Technical enquiries email: sales@murata-ps.com, tel: +1 508 339 3000
MDC_MDC_OKY-T/3,T/5-D12 Series.B03 Page 1 of 22
Trim
Performance Specifi cations and Ordering Guide
ORDERING GUIDE
Output Input
R/N (mVp-p)
Power
(Watts)
Root Model ➁
OKY-T/3-D12N-C
OKY-T/3-D12P-C
OKY-T/5-D12N-C
OUT
V
(Volts)
0.75-5.5
0.75-5.5 ➆
0.75-5.5
IOUT
(Amps
max)
3 15.3 25 ±0.1% ±0.2% 12 8.3-14 80 1.34 91.5% 93%
➆
3 15.3 25 ±0.1% ±0.2% 12 8.3-14 80 1.34 91.5% 93%
5 25.5 25 ±0.2% ±0.5% 12 8.3-14 80 2.24 91.5% 93%
➅
Adjustable Output 3 and 5-Amp DOSA-SMT DC/DC Converters
➄ Regulation (Max.)➂
VIN Nom.
(Volts)
OKY-T/3,T/5-D12 Series
Range
(Volts)
IIN,
no load
(mA)
full load
(Amps) Case C72 ➀ PinoutMax. Line Load Min. Typ.
IIN,
Effi ciency
0.47 x 0.82 x 0.28
(11.9 x 20.8 x 7.1)
0.47 x 0.82 x 0.28
(11.9 x 20.8 x 7.1)
0.47 x 0.82 x 0.28
(11.9 x 20.8 x 7.1)
Package
P78
P78
P78
➀ Dimensions are in inches (mm).
➁ These are partial model numbers. Please refer to the part number structure for complete ordering part numbers.
➂ All specifications are at nominal line voltage, Vout=nominal (5V for D12 models) and full load, +25 ˚C. unless
otherwise noted.
Output capacitors are 1 µF ceramic and 10 µF electrolytic in parallel. Input cap is 22 µF. See detailed specifica-
tions.
I/O caps are necessary for our test equipment and may not be needed for your application.
PART NUMBER STRUCTURE
O KY -/ D12-T 5 C-
Output
Confi guration:
Single Output,
Unipolar, Low Voltage
Non-Isolated Surface Mount
Trimmable Output
Voltage Range
0.75-5.5V
Maximum Rated Output
Current in Amps
fVin must be 2V or higher than Vout for 3.3 to 5V outputs.
gRipple and Noise is shown at Vout=1V. See specs for details.
OUT = 5.1V at IOUT = 5A.
➅Max. V
➆Max. VOUT = 5.1V at IOUT = 3A.
N
RoHS Hazardous
Substance Compliance
C = RoHS6 (does not claim EU RoHS exemption
7b–lead in solder)
On/Off Polarity
P = Positive Polarity
N = Negative Polarity
Input Voltage Range
8.3-14V
Note: Some model number combinations
may not be available. Contact Murata
Power Solutions for availability.
Technical enquiries email: sales@murata-ps.com, tel: +1 508 339 3000www.murata-ps.com
MDC_MDC_OKY-T/3,T/5-D12 Series.B03 Page 2 of 22
MECHANICAL SPECIFICATIONS
TOP VIEW
CORNER (FARSIDE)
11.9
0.47
NOZZLE
PICKUP
POINT
PIN #1 THIS
20.8
0.82
SIDE VIEW
MTG PLANE
10.67
0.420
REF
1.59
0.063
OKY-T/3,T/5-D12 Series
Adjustable Output 3 and 5-Amp DOSA-SMT DC/DC Converters
ISOMETRIC
VIEW
5.64
0.222
REF
END VIEW
6.2
0.25
PIN #1
INPUT/OUTPUT CONNECTIONS
OKY-T/3, -T/5
Pin Function
1 On/Off Control*
2+VIN
3 Ground (Common)
4 Trim
5+V
*The Remote On/Off can be provided with
either positive (P suffi x) or negative (N
suffi x) polarity
OUT
BOTTOM VIEW
1.59
0.063
TYP
2.29
0.090
TYP
3
4 5
2
0.25
0.010
8.63
0.340
12.69
0.500
17.52
0.690
MATERIAL:
SMT PINS: COPPER ALLOY
FINISH: (ALL PINS)
GOLD (5u"MIN) OVER NICKEL (50u" MIN)
1
4.57
0.180
1.5
0.06
8.63
0.340
0.47
REF
1.8
0.07
Figure 2. OKY-T/3, -T/5 Mechanical Outline
0.82 REF
0.060
REF
21
35
4
MIN0.120
0.135 MAX
RECOMMENDED PAD LAYOUT
Dimensions are in inches (mm shown for ref. only).
Third Angle Projection
Tolerances (unless otherwise specified):
.XX ± 0.02 (0.5)
.XXX ± 0.010 (0.25)
Angles ± 1˚
Components are shown for reference only.
0.070
REF
0.095 MIN
0.110 MAX
Technical enquiries email: sales@murata-ps.com, tel: +1 508 339 3000www.murata-ps.com
MDC_MDC_OKY-T/3,T/5-D12 Series.B03 Page 3 of 22
Performance and Functional Specifi cations
See Note 1
Input
Input Voltage Range See Ordering Guide and Note 7.
Isolation Not isolated
Start-Up Voltage 7.5 V. min, 8.25 V. max
Undervoltage Shutdown (see Note 15) 7.3 V. min, 8.05 V. max
Overvoltage Shutdown None
Refl ected (Back) Ripple Current (Note 2) 20 mA pk-pk
Internal Input Filter Type Capacitive
Recommended External Fuse 6A
Reverse Polarity Protection N/A. See fuse information.
Input Current:
Full Load Conditions See Ordering Guide
Inrush Transient 0.4 A2Sec.
Shutdown Mode (Off, UV, OT) 5 mA
Output in Short Circuit 60 mA
No Load 80 mA
Low Line (Vin=Vmin, 5Vout) 1.93 A. (OKY-T/3-D12)
3.24 A. (OKY-T/5-D12)
Remote On/Off Control (Note 5)
Negative Logic (“N” model suffi x) ON = Open pin or ground to +0.4V. max.
OFF = +1.5V min. to +Vin
Current 1 mA max.
Positive Logic (“P” model suffi x) ON = Open pin (internally pulled up) or
+7.8Vdc to +Vin max.
OFF = Ground pin to +0.4V. max.
Current 1 mA max.
Output
Output Power 15.3W max. (OKY-T/3)
25.5W max. (OKY-T/5)
Output Voltage Range See Ordering Guide
Minimum Loading No minimum load
Accuracy (50% load, untrimmed) ±2 % of Vnominal
Voltage Output Range (Note 13) See Ordering Guide
Overvoltage Protection (Note 16) None
Temperature Coeffi cient ±0.02% per °C of Vout range
Ripple/Noise (20 MHz bandwidth) See Ordering Guide and note 8
Line/Load Regulation See Ordering Guide and note 10
Effi ciency See Ordering Guide
Maximum Capacitive Loading (Note 14)
Cap-ESR=0.001 to 0.01 Ohms 1,000 F
Cap-ESR >0.01 Ohms 3,000 F
Current Limit Inception (Note 6)
(98% of Vout setting, after warm up) 7.5 Amps max.
Short Circuit Mode
Short Circuit Current Output 2 A
Protection Method Hiccup autorecovery upon overload
removal. (Note 17)
Short Circuit Duration Continuous, no damage
(output shorted to ground)
Prebias Startup Converter will start up if the external
output voltage is less than Vnominal.
Dynamic Characteristics
Dynamic Load Response 90Sec max. to within ±2% of fi nal value
(50-100-50% load step, di/dt=2.5A/μSec)
Start-Up Time 8 mSec for Vout=nominal
(Vin on or On/Off to Vout regulated)
Switching Frequency 320 KHz
± 30
KHz
OKY-T/3,T/5-D12 Series
Adjustable Output 3 and 5-Amp DOSA-SMT DC/DC Converters
Environmental
Calculated MTBF
Telecordia method (4a) OKY-T/3-D12N-C: 10,155,200 hours
Calculated MTBF
MIL-HDBK-217N2 method (4b) OKY-T/3-D12N-C: 6,309,035 hours
Operating Temperature Range (Ambient, vertical mount)
See derating curves -40 to +85 ˚C. with derating (Note 9)
Operating PC Board Temperature -40 to +100 ˚Celsius max., no derating (12)
Storage Temperature Range -55 to +125 deg. C.
Thermal Protection/Shutdown +130 ˚Celsius
Relative Humidity to 85%/+85 ˚C., non-condensing
Physical
Outline Dimensions See Mechanical Specifi cations
Weight 0.1 ounces (2.8 grams)
Electromagnetic Interference Designed to meet FCC part 15, class B,
EN55022 and CISPR22 class B conducted
and radiated (may need external fi lter)
Safety Designed to meet UL/cUL 60950-1, CSA C22.2 No. 60950-1, IEC/EN 60950-1
Restriction of Hazardous Substances RoHS6 (
7b–lead in solder
MSL Rating 2
Absolute Maximum Ratings
Input Voltage (Continuous or transient) 0 V.to +15 Volts max.
On/Off Control 0 V. min. to +Vin max.
Input Reverse Polarity Protection See Fuse section
Output Current (Note 7) Current-limited. Devices can withstand a
sustained short circuit without damage.
The outputs are not intended to accept
appreciable reverse current.
Storage Temperature -55 to +125 ˚C.
Lead Temperature See soldering specifi cations
Absolute maximums are stress ratings. Exposure of devices to greater than any of
any of these conditions may adversely affect long-term reliability. Proper operation
under conditions other than those listed in the Performance/Functional Specifi cations
Table is not implied or recommended.
Specifi cation Notes:
(1) Specifi cations are typical at +25 °C, Vin=nominal (+12V.), Vout=nominal (+5V), full load, external caps and
natural convection unless otherwise indicated. Extended tests at full power must supply substantial forced
airfl ow.
All models are tested and specifi ed with external 1 F paralleled with 10F ceramic/tantalum output
capacitors and a 22 F external input capacitor. All capacitors are low ESR types. These capacitors are
necessary to accommodate our test equipment and may not be required to achieve specifi ed performance
in your applications. However, Murata Power Solutions recommends installation of these capacitors. All
models are stable and regulate within spec under no-load conditions.
(2) Input Back Ripple Current is tested and specifi ed over a 5 Hz to 20 MHz bandwidth. Input fi ltering is Cin=2 x
100 F tantalum, Cbus=1000 F electrolytic, Lbus=1 H.
(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.
(4a) Mean Time Before Failure is calculated using the Telcordia (Belcore) SR-332 Method 1, Case 3, ground fi xed
conditions, Tpcboard=+25 ˚C, full output load, natural air convection.
(4b) Mean Time Before Failure is calculated using the MIL-HDBK-217N2 method, ground benign, +25ºC., full
output load, natural convection.
(5) The On/Off Control Input should use either a switch or an open collector/open drain transistor referenced
to -Input Common. A logic gate may also be used by applying appropriate external voltages which do not
exceed +Vin.
(6) Short circuit shutdown begins when the output voltage degrades approximately 2% from the selected
setting.
does not claim EU RoHS exemption
)
Technical enquiries email: sales@murata-ps.com, tel: +1 508 339 3000www.murata-ps.com
MDC_MDC_OKY-T/3,T/5-D12 Series.B03 Page 4 of 22
OKY-T/3,T/5-D12 Series
Adjustable Output 3 and 5-Amp DOSA-SMT DC/DC Converters
Specifi cation Notes, Cont.:
(7) For W5 models, the Input Voltage must exceed the Output Voltage at all times by the ratio of Vin >= (1.15 x
Vout). Please see the separate W5 data sheet.
(8) Output noise may be further reduced by adding an external fi lter. 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.
(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) Other input or output voltage ranges will be reviewed under scheduled quantity special order.
(12) Maximum PC board temperature is measured with the sensor in the center of the converter.
(13) Do not exceed maximum power specifi cations when adjusting the output trim.
(14) The maximum output capacitive loads depend on the the Equivalent Series Resistance (ESR) of the external
output capacitor and, to a lesser extent, the distance and series impedance to the load. Larger caps will
reduce output noise but may change the transient response. Newer ceramic caps with very low ESR may
require lower capacitor values to avoid instability. Thoroughly test your capacitors in the application. Please
refer to the Output Capacitive Load Application Note.
(15) Do not allow the input voltage to degrade lower than the input undervoltage shutdown voltage at all times.
Otherwise, you risk having the converter turn off. The undervoltage shutdown is not latching and will
attempt to recover when the input is brought back into normal operating range.
(16) The outputs are not intended to sink appreciable reverse current.
(17) “Hiccup” overcurrent 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 overheating and damaging the converter. Once the fault is removed, the converter
immediately recovers normal operation.
Output Voltage Adustment
The output voltage may be adjusted over a limited range by connecting an
external trim resistor (Rtrim) between the Trim pin and Ground. The Rtrim
resistor must be a 1/10 Watt precision metal fi lm type, ±1% accuracy or
better with low temperature coeffi cient, ±100 ppm/oC. or better. Mount the
resistor close to the converter with very short leads or use a surface mount
trim resistor.
Soldering Guidelines
Murata Power Solutions recommends the specifi cations below when installing these
converters. These specifi cations vary depending on the solder type. Exceeding these
specifi cations may cause damage to the product. Be cautious when there is high
atmospheric humidity. We strongly recommend a mild pre-bake (100 ºC. for 30
minutes). Your production environment may differ therefore please thoroughly review
these guidelines with your process engineers.
Reflow Solder Operations for surface-mount products (SMT)
For Sn/Ag/Cu based solders:
Preheat Temperature Less than 1 ºC. per second
Time over Liquidus 45 to 75 seconds
Maximum Peak Temperature 260 ºC.
Cooling Rate Less than 3 ºC. per second
For Sn/Pb based solders:
Preheat Temperature Less than 1 ºC. per second
Time over Liquidus 60 to 75 seconds
Maximum Peak Temperature 235 ºC.
Cooling Rate Less than 3 ºC. per second
In the tables below, the calculated resistance is given. Do not exceed the
specifi ed limits of the output voltage or the converter’s maximum power
rating when applying these resistors. Also, avoid high noise at the Trim
input. However, to prevent instability, you should never connect any capacitors to Trim.
OKY-T/3-D12, -T/5-D12
Output Voltage Calculated Rtrim (KΩ)
5.0 V. 1.472
3.3 V. 3.122
2.5 V. 5.009
2.0 V. 7.416
1.8 V. 9.024
1.5 V. 13.05
1.2 V. 22.46
1.0 V. 41.424
0.7525 V. ∞ (open)
Resistor Trim Equation, D12 models:
10500
RTRIM (:) =
_____________
VOUT – 0.7525V
–1000
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MDC_MDC_OKY-T/3,T/5-D12 Series.B03 Page 5 of 22
OKY-T/3,T/5-D12 Series
Adjustable Output 3 and 5-Amp DOSA-SMT DC/DC Converters
APPLICATION 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. We
recommend a time delay fuse installed in the ungrounded input supply line
with a value which is approximately twice the maximum line current, calculated at the lowest input voltage.
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 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 operation 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
capacitor inputs), the converter shuts off and then restarts as the external
capacitor recharges. Such situations could oscillate. To prevent this, make
sure the operating 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
input voltage regulation. Since real-world voltage sources have fi nite imped-
ance, 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 components, circuits and layout as shown in the fi gures below. External input
capacitors (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 temperature rise from refl ected AC current dissipated inside capacitor ESR.
TO
OSCILLOSCOPE
L
+
–
V
IN
+
–
CIN = 2 x 100µF, ESR < 700mΩ @ 100kHz
BUS
= 1000µF, ESR < 100mΩ @ 100kHz
C
BUS
= 1µH
L
BUS
C
BUS
Figure 2: Measuring Input Ripple Current
CURRENT
PROBE
C
IN
+INPUT
-INPUT
In the fi gure, the two copper strips simulate real-world printed circuit
impedances between the power supply and its load. In order to minimize circuit
errors and standardize tests between units, scope measurements should be
made using BNC connectors or the probe ground should not exceed one half
inch and soldered directly to the fi xture.
Technical enquiries email: sales@murata-ps.com, tel: +1 508 339 3000www.murata-ps.com
MDC_MDC_OKY-T/3,T/5-D12 Series.B03 Page 6 of 22
Adjustable Output 3 and 5-Amp DOSA-SMT DC/DC Converters
COPPER STRIP
+OUTPUT
R
C1
-OUTPUT
COPPER STRIP
C1 = 0.1µF CERAMIC
C2 = 10µF TANTALUM
LOAD 2-3 INCHES (51-76mm) FROM MODULE
Figure 3: Measuring Output Ripple and Noise (PARD)
C2
SCOPE
Minimum Output Loading Requirements
All models regulate within specifi cation and are stable under no load to full
load conditions. Operation under no load might however slightly increase
output 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. The temperature sensor is typically
located adjacent to the switching controller, approximately in the center of the
unit. See the Performance and Functional Specifi cations.
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 the next section 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 current or reduced airfl ow as long as the average 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 very low fl ow rates (below about 25 LFM) are similar to “natural
convection”, that is, not using fan-forced airfl ow.
Murata Power Solutions 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 understand the enclosure geometry, entry/exit orifi ce areas and
the fan fl owrate specifi cations.
LOAD
OKY-T/3,T/5-D12 Series
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. 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 voltage to ramp up to its
rated value. It is not necessary to power down and reset the converter for the
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 damaging the converter.
Output Fusing
The converter is extensively protected against current, voltage and temperature
extremes. However your output application circuit may need additional protection. 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 also
commonly 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
in normal operation as long as the average output power is not exceeded. 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 (approximately 98% of nominal output voltage for most models), 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 appropriate value.
If the short-circuit condition persists, another shutdown cycle will initiate. This
rapid on/off cycling is called “hiccup mode”. The hiccup cycling reduces the
average output current, thereby preventing excessive internal temperatures
and/or component damage. A short circuit can be tolerated indefi nitely.
The “hiccup” system differs from older latching short circuit systems
because you do not have to power down the converter to make it restart. The
system will automatically restore operation as soon as the short circuit condition is removed.
Technical enquiries email: sales@murata-ps.com, tel: +1 508 339 3000www.murata-ps.com
MDC_MDC_OKY-T/3,T/5-D12 Series.B03 Page 7 of 22
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