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78250J Series
MAX250/MAX251 Compatible Converter SM Transformers
FEATURES J-STD-020D reflow 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 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. For through hole versions see 78250 datasheet.
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CHARACTERISTICS 78250JC
Parameter
Primary Inductance, LP Leakage Inductance, L
L
Interwinding Capacitance, C WW
Primary D.C. Resistance, R DC
Volt-time Product, Et
Turns Ratio
Conditions 10kHz, 100mV 100kHz, 100mV 100kHz, 100mV <0.1VDC Pins1/2 or 2/3
Min.
Typ.
Max.
Units
1.0
2.0
2.5
mH
0.6
3.0
μH
48
90
pF
0.7
2.0
Ω
50
Vμs
1:1
CHARACTERISTICS 78250JVC
Parameter
Primary Inductance, L P
Leakage Inductance, L L
Interwinding Capacitance, CWW Primary D.C. Resistance, R
DC
Volt-time Product, Et
Turns Ratio
Conditions 10kHz, 100mV 100kHz, 100mV 100kHz, 100mV <0.1VDC Pins1/2 or 2/3
Min.
Typ.
Max.
Units
1.0
2.0
2.5
mH
35
40
μH
4
10
pF
0.9
1.8
Ω
50
Vμs
1:1
ORDER CODE DETAILS Order Code
78250JC / 78250JVC 78250JC-R / 78250JVC-R
Package Type 6 Pin SM 6 Pin SM
Packaging Type Tube
Tape & Reel
Quantity 50 500
ABSOLUTE MAXIMUM RATINGS Operating free air temperature range Storage temperature range Lead temperature 1.5mm from case for 10 seconds Peak current, I
PK
Isolation voltage 78250(J)C (flash tested for 1 second) Isolation voltage 78250V(J)C (flash tested for 1 second)
-40°C to 85°C -50°C to 125°C 300°C 300mA 1.5kVrms 4.0kVrms
All specifications typical at T =25°C A
TECHNICAL NOTES
ISOLATION VOLTAGE
REPEATED HIGH-VOLTAGE ISOLATION TESTING
‘Hi Pot Test’, ‘Flash Tested’, ‘Withstand Voltage’, ‘Proof Voltage’, ‘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 operation?”
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 voltage 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 correctly 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-accessible circuitry according to safety standard requirements.
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 environment. 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 depend 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 therefore 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 recognized parts rated for better than functional isolation where the wire enamel insulation is always supplemented by a further insulation system of physical spacing or barriers.
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PACKAGE SPECIFICATIONS MECHANICAL DIMENSIONS
78250J Series
MAX250/MAX251 Compatible Converter SM Transformers
0.354 (9.0) Max.
0.5 (12.70) 0.375 (9.52) Max.
78250JC
XYYWW
Primary Secondary
1
6
2
5*
3
4
0.25 (6.35)
0.012 (0.30) 0.008 (0.20)
0.035 (0.90)
0.1 (2.54)
RECOMMENDED FOOTPRINT DETAILS
0.025 (0.63) 0.021 (0.53)
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.