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Product Overview
MUR3040CT integrates two 15A fast-recovery diodes in a common-cathode TO-220AB package. Its 400V reverse-voltage rating and shared output node make it a practical option for positive center-tapped rectification in switching power supplies and charger secondary stages.
The 30A total device rating comprises two 15A diode paths. Evaluate each branch at its own current waveform and operating temperature when calculating conduction loss and the required cooling.
Key Features
● 400V repetitive peak reverse voltage and two 15A diode paths.
● 50ns maximum reverse-recovery time under the specified 0.5A test condition.
● 1.3V maximum forward voltage at 15A and 25°C.
● 200A non-repetitive surge current per diode for a 8.3ms pulse.
Key Specifications
| Parameter | Value and conditions |
| Configuration / package | Dual common cathode / TO-220AB |
| Forward current | 30A per device; 15A per diode |
| Repetitive peak reverse voltage | 400V |
| Forward voltage | 0.95V typ at IF = 15A, Tj = 125°C 1.3V max at IF = 15A, Tj = 25°C |
| Reverse recovery time | 50ns max; Tj = 25°C, IF = 0.5A, IR = 1.0A, Irr = 0.25A |
| Surge current | 200A per diode; non-repetitive, t = 8.3ms |
| Junction to case thermal resistance | 2.5°C/W |
| Junction temperature range | −55°C to +150°C |
Current capability depends on case temperature and cooling. Use the datasheet derating curve when determining operating current.
Electrical Configuration and Pinout
Two separate anodes connect to a shared cathode. With the marking face toward you and the leads pointing down, the lead functions are A1, K and A2 from left to right. The exposed metal tab is also connected to K.
Figure 1. Circuit and connection detail from the MUR3040CT datasheet, page 1. A = anode; K = cathode.
| Connection | Function |
| Left lead | A1 — first diode anode |
| Center lead | K — common cathode |
| Right lead | A2 — second diode anode |
| Metal tab | K — electrically connected to the common cathode |
Typical Applications
● Positive center-tapped industrial SMPS rectification.
● Transformer-secondary rectification in battery chargers.
● DC converter outputs requiring a common cathode.
Designed for Positive Center Tapped Outputs
In a center-tapped secondary circuit, the two winding ends connect to A1 and A2 while the common cathode feeds the positive rectified output. The winding center tap provides the return connection. Both rectifier paths are combined in one package.
Design Notes
Evaluate each diode at its own current waveform and duty cycle. The 30A total device rating does not mean one junction can carry 30A. Check reverse-voltage peaks, including switching transients, against the 400V rating.
The metal tab carries the common cathode potential. If the heatsink must remain at a different potential, use an appropriate insulating mounting interface and include its thermal resistance.
The 50ns recovery limit uses the low-current test condition in the parameter table. Evaluate recovery at the application current and temperature. The 200A surge specification is non-repetitive and must not be used as a repetitive overload rating.
FAQ
The cathodes share the center connection and metal tab according to the datasheet symbol.
No. The sheet distinguishes 30 A per device and 15 A per diode. Use the actual alternating duty cycle for each junction.
Only if the common cathode node is allowed to be at ground. Otherwise use a rated electrical insulator and recheck thermal performance.
It is the maximum recovery time under the stated low-current test. It is a comparison point, not a complete prediction of circuit overshoot or EMI.
