FEATURES
n Maxim Compatible
n 3.3V and 5V Versions
n Isolation to 4kV
n Frequency Range to 500kHz
n Toroidal Construction
n Industrial Standard Pinout
n UL 94V-0 Package Material
n Fully Encapsulated
n Low Profile
n Surface Mount Available
DESCRIPTION
The 78253 series of converter transformers
are specifically designed for use with the
MAX253 chip set to provide isolated power
supplies. The 5V version can supply 1W and
the 3.3V version can supply 500mW. A
centre tapped secondary winding allows for
full bridge, half bridge or voltage doubling.
The surface mount devices are fully
compatible with CECC00802 to 280°C
which allows them to be placed and reflowed
with IC’s thus reducing time and cost in
production.
78253/35(M) CHARACTERISTICS
Parameter Conditions MIN TYP MAX Units
Primary Inductance, LP 100kHz, 250mV 0.30 0.38 0.46 mH
Secondary Inductance, LS 100kHz, 250mV 1.60 2.00 2.40 mH
Leakage Inductance, LL 100kHz, 250mV 0.30 1.00 µH
Interwinding Capacitance, CWW 100kHz, 250mV 30 50 pF
D.C. Resistance, RDC >0.1VDC 0.40 1.00 Ω
Volt-time Product, ET 5kHz, 5V 50 80 Vµs
78253/55(M) CHARACTERISTICS
Parameter Conditions MIN TYP MAX Units
Primary Inductance, LP 100kHz, 250mV 0.60 0.83 1.10 mH
Secondary Inductance, LS 100kHz, 250mV 1.10 1.40 1.70 mH
Leakage Inductance, LL 100kHz, 250mV 0.35 1.00 µH
Interwinding Capacitance, CWW 100kHz, 250mV 30 50 pF
D.C. Resistance, RDC >0.1VDC 0.70 1.50 Ω
Volt-time Product, ET 5kHz, 5V 50 65 Vµs
78253/35(M)V CHARACTERISTICS
Parameter Conditions MIN TYP MAX Units
Primary Inductance, LP 100kHz, 20mV 110 142 185 µH
Secondary Inductance, LS 100kHz, 20mV 550 710 850 µH
Leakage Inductance, LL 100kHz, 250mV 3.00 5.00 µH
Interwinding Capacitance, CWW 100kHz, 250mV 4.20 8.00 pF
D.C. Resistance, RDC >0.1VDC 0.30 0.50 Ω
Volt-time Product, ET 5kHz, 5V 30 42 Vµs
78253/55(M)V CHARACTERISTICS
Parameter Conditions MIN TYP MAX Units
Primary Inductance, LP 100kHz, 20mV 190 240 310 µH
Secondary Inductance, LS 100kHz, 20mV 350 444 540 µH
Leakage Inductance, LL 100kHz, 250mV 5.20 8.00 µH
Interwinding Capacitance, CWW 100kHz, 250mV 4.20 8.00 pF
D.C. Resistance, RDC >0.1VDC 0.40 0.60 Ω
Volt-time Product, ET 5kHz, 5V 25 32 Vµs
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 400mA
Isolation voltage 78253/XX(M) (flash tested for 1 second) 1500VDC
Isolation voltage 78253/XX(M)V (flash tested for 1 second) 4000VDC
ABSOLUTE MAXIMUM RATINGS
All specifications typical at TA= 2 5 ° C .
SELECTION GUIDE
Input Output Output Isolation Turns Package
Voltage Voltage Current Voltage Ratio Style
Order Code (V) (V) (mA Max) (VDC)
78253/35 3.3 5.0 100 1500 1:√5 DIP
78253/35M SM
78253/55 5.0 5.0 200 1500 1:1.31 DIP
78253/55M SM
78253/35V 3.3 5.0 100 4000 1:√5 DIP
78253/35MV SM
78253/55V 5.0 5.0 200 4000 1:1.36 DIP
78253/55MV SM
78253 SERIES
MAX253 Compatible Converter Transformers
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