DFLT30A-7

The DFLT30A-7 from Diodes Incorporated is a unidirectional transient voltage suppressor (TVS) diode in the compact PowerDI 123 surface-mount package. It is part of the DFLT series covering standoff voltages from 5.0 V to 51 V, providing scalable protection across common system voltages.

The DFLT30A provides 30 V reverse standoff voltage (VRWM), making it suitable for protecting 24 V nominal rails (24 V + 25% tolerance = 30 V maximum). The 33.3 V minimum breakdown voltage ensures the TVS does not conduct during normal operation, while the 36.8 V maximum breakdown guarantees it starts clamping before the protected circuitry is damaged.

Under a transient event (IEC 61000-4-5 8/20 us or 10/1000 us waveform), the device clamps at a maximum of 48.4 V at 4.65 A peak pulse current. This clamping voltage provides the protection margin that determines whether the downstream IC survives the transient.

The PowerDI 123 package achieves a very low 6C/W junction-to-soldering-point thermal resistance, enabling efficient heat transfer during surge events. The package is rated for 225 W peak pulse power on a 10/1000 us waveform and 1125 W on an 8/20 us waveform. The 1 W steady-state DC power dissipation allows the device to handle continuous reverse power without thermal runaway.

The DFLT30A-7 is AEC-Q101 qualified for automotive applications and uses green molding compound (no bromine, no antimony). The -7 suffix indicates tape-and-reel packaging with 3000 units per reel. The marking code for DFLT30A is not specified in the available data sheet excerpt.

**Avalanche TVS Operation:** The DFLT30A uses an avalanche (Zener) junction designed to handle high transient power. In normal operation (voltage below VRWM = 30 V), the TVS draws only leakage current (1 uA max). When a transient exceeds the breakdown voltage (VBR = 33.3-36.8 V), the junction avalanches and clamps the voltage.

**Clamping Mechanism:** During an avalanche event, the TVS presents a low dynamic impedance, holding the voltage close to VBR for moderate currents. At the rated peak pulse current (IPP = 4.65 A), the clamping voltage rises to VC = 48.4 V maximum due to the device’s dynamic resistance. Lower surge currents result in lower clamping voltages.

**Unidirectional Configuration:** The DFLT30A is unidirectional, meaning it clamps only positive transients (with respect to the cathode). For negative transients, the internal diode forward-biases and clamps at approximately 3.5 V at 12 A. Bidirectional protection requires two devices in back-to-back configuration or a bidirectional TVS.

**PowerDI 123 Thermal Advantage:** The PowerDI 123 package features a large cathode tab that solders directly to the PCB copper pour. With RthJS of only 6C/W, heat from the avalanche event transfers quickly to the PCB, reducing peak junction temperature and improving surge survival. This thermal advantage enables the 225 W peak pulse power rating in a package smaller than SMA/SMB.