KMP_78250C_C08 Page 1 of 3
78250 Series
MAX250/MAX251 Compatible Converter Transformers
www.murata-ps.com
www.murata-ps.com/support
For full details go to
www.murata-ps.com/rohs
FEATURES
RoHS compliant
Maxim MAX250/MAX251 compatible
Isolation to 4kVrms
Industry-standard pinout
Surface mount option
UL 94 V-0 package materials
Low profile
Toroidal construction
Fully encapsulated
Industrial temperature range
DESCRIPTION
The 78250 series of converter transformers
are specifically designed for use with Maxim
chipsets to provide isolated RS232 interfaces.
Carefully controlled turns ratios ensure consistent
performance whilst a toroidal construction
minimises EMI.
Surface-mount parts
The surface-mount (M suffix) products are not
recommended for new designs. For existing designs,
however, Murata Power Solutions will continue to
manufacture and fully support these parts.
For recommended alternatives please refer to the
78250J Series datasheet.
CHARACTERISTICS 78250C/78250MC
Parameter Conditions Min. Typ. Max. Units
Primary Inductance, LP10kHz, 100mV 1.0 2.0 2.5 mH
Leakage Inductance, LL100kHz, 100mV 2.0 3.0 μH
Interwinding Capacitance, CWW 100kHz, 100mV 69 90 pF
Primary D.C. Resistance, RDC <0.1VDC 1.0 2.0 Ω
Volt-time Product, Et Pins1/2 or 2/3 50 Vμs
CHARACTERISTICS 78250VC/78250MVC
Parameter Conditions Min. Typ. Max. Units
Primary Inductance, LP10kHz, 100mV 1.0 2.0 2.5 mH
Leakage Inductance, LL100kHz, 100mV 35 40 μH
Interwinding Capacitance, CWW 100kHz, 100mV 9 12 pF
Primary D.C. Resistance, RDC <0.1VDC 1.4 1.8 Ω
Volt-time Product, Et Pins1/2 or 2/3 50 Vμs
ORDER CODE DETAILS
Order Code Package Type Packaging Type Quantity
78250C / 78250VC 6 Pin DIL Tube 50
78250MC / 78250MVC 6 Pin SM Tube 50
78250MC-R / 78250MVC-R 6 Pin SM Tape & Reel 500
ABSOLUTE MAXIMUM RATINGS
Operating free air temperature range -40°C to 85°C
Storage temperature range -50°C to 125°C
Lead temperature 1.5mm from case for 10 seconds 300°C
Peak current, IPK 300mA
Isolation voltage 78250(M)C (flash tested for 1 second) 1.5kVrms
Isolation voltage 78250(M)VC (flash tested for 1 second) 4.0kVrms
All specifications typical at TA=25°C
TECHNICAL NOTES
ISOLATION VOLTAGE
‘Hi Pot Test’, ‘Flash Tested’, ‘Withstand Voltage’, ‘Proof Volt-
age’, ‘Dielectric Withstand Voltage’ & ‘Isolation Test Voltage’
are all terms that relate to the same thing, a test voltage,
applied for a specified time, across a component designed
to provide electrical isolation, to verify the integrity of that
isolation.
All products in this series are 100% production tested at
their stated isolation voltage.
A question commonly asked is, “What is the continuous
voltage that can be applied across the part in normal opera-
tion?”
For a part holding no specific agency approvals both input
and output should normally be maintained within SELV limits
i.e. less than 42.4V peak, or 60VDC. The isolation test volt-
age represents a measure of immunity to transient voltages
and the part should never be used as an element of a safety
isolation system. The part could be expected to function cor-
rectly with several hundred volts offset applied continuously
across the isolation barrier; but then the circuitry on both
sides of the barrier must be regarded as operating at an
unsafe voltage and further isolation/insulation systems must
form a barrier between these circuits and any user-acces-
sible circuitry according to safety standard requirements.
REPEATED HIGH-VOLTAGE ISOLATION TESTING
It is well known that repeated high-voltage isolation
testing of a barrier component can actually degrade
isolation capability, to a lesser or greater degree
depending on materials, construction and environ-
ment. This series has toroidal isolation transformers,
with no additional insulation between primary and
secondary windings of enameled wire. While parts
can be expected to withstand several times the
stated test voltage, the isolation capability does de-
pend on the wire insulation. Any material, including
this enamel (typically polyurethane) is susceptible
to eventual chemical degradation when subject to
very high applied voltages thus implying that the
number of tests should be strictly limited. We there-
fore strongly advise against repeated high voltage
isolation testing, but if it is absolutely required, that
the voltage be reduced by 20% from specified test
voltage.
This consideration equally applies to agency recog-
nised parts rated for better than functional isolation
where the wire enamel insulation is always supple-
mented by a further insulation system of physical
spacing or barriers.
KMP_78250C_C08 Page 2 of 3
78250 Series
MAX250/MAX251 Compatible Converter Transformers
www.murata-ps.com/support
PACKAGE SPECIFICATIONS
MECHANICAL DIMENSIONS
RECOMMENDED FOOTPRINT DETAILS
0.354
(9.0) Max.
0.375
(9.52) Max.
0.5
(12.70)
0.025 (0.63)
0.021 (0.53)
0.035 (0.90)
0.012±0.30
(0.008±0.20)
0.25
(6.35)
0.1 (2.54)
78250MC
XYYWW
0.135±0.02
(3.44±0.50)
0.25
(6.35)
0.354
(9.0) Max.
0.375
(9.52) MAX
Primary PrimarySecondary Secondary
0.012(0.30)
0.008(0.20) 0.40
(10.16)
0.025 (0.63)
0.021 (0.53)
0.1
(2.54)
78250C
XYYWW
6 Pin DIL 6 Pin SM
SOLDERING INFORMATION1
Pin finish Matte tin
Peak wave solder temperature 300˚C for 10 seconds
Peak reflow temperature 220˚C2
1 For further information, please visit www.murata-ps.com/rohs
2 For high temperature reflow parts see 78250J Series.
1
2
3
6
4
6
5*
4
1
2
3
0.10 (2.54)
0.10 (2.54)
Ø0.05 (1.20)+0.006 (0.15)
-0.000 (0.00)
6 Pin DIL 6 Pin SM
Unless otherwise stated all dimensions in inches (mm)
±0.01 (0.25). All pins on a 0.1 (2.54) pitch and within
±0.01 (0.25) of true position.
Unless otherwise stated all dimensions in inches (mm) ±0.01 (0.25).
All pins on a 0.1 (2.54) pitch and within ±0.01 (0.25) of true position.
* Pin 5 is connected to secondary center tap. Package Weight 1.0g TYP.
0.45
(11.50)
0.10 (2.54)
0.04
(1.00)
0.06 (1.60)
TUBE OUTLINE DIMENSIONS
0.023±0.005
(0.60±0.15)
0.16 (4.00)
0.22 (5.50)
0.43
(10.95)
0.51
(12.95)
0.15
(3.80)
0.62 (15.70)
Unless otherwise stated all
dimensions in inches (mm)
±0.01 (0.25).
Tube length: 18.3±0.08 (465±2).
Tube material: Antistatic coated
clear pvc.
KMP_78250C_C08 Page 3 of 3
78250 Series
MAX250/MAX251 Compatible Converter Transformers
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. Specifications are subject to change without
notice. © 2018 Murata Power Solutions, Inc.
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/
TAPE & REEL SPECIFICATIONS
REEL OUTLINE DIMENSIONS
TAPE OUTLINE DIMENSIONS
1.20
(30.4) Max.
0.94-1.08 (23.9-27.4)
0.53 (13.50)
0.50 (12.80)
0.059 (1.50)
Min.
2.36 (60) Min.
0.80 (20.20) Min.
3.9 (100)
Min.
Leader section
15.7 (400) Min.
Goods
enclosure
section
Trailer section
6.3 (160) Min.
Ø15.039 (382) Max.
Ø
Ø
*
0.96 (24.4)
1.04 (26.4)
g
g
Unless otherwise stated all
dimensions in inches (mm) ±0.01(0.25).
* Includes flange distortion at outer edge.
g Measured at hub.
0.024 (0.60) Max.
0.283 (7.20)
0.369 (9.37)
Direction of unreeling
0.069 (1.75)
0.453 (11.50)
0.157 (4.00) 0.079 (2.00)
0.472 (12.00)
Cover tape
0.059 (1.50 )
+0.004
-0.000 +0.10
-0.00
0.945 (24.00 )
+0.012
-0.004
+0.30
-0.10
78250C
XYYWW
Unless otherwise stated all
dimensions in inches (mm) ±0.01(0.25).
