The SI4435DDY-T1-GE3 from Vishay Siliconix is a P-Channel 30-V (D-S) TrenchFET power MOSFET in an 8-pin SOIC (SO-8) package (4.88 x 3.89 x 1.54 mm). It is halogen-free per IEC 61249-2-21 and RoHS compliant. Key specifications: VDS = -30V, VGS = plus\/minus 20V, ID = -8.1A (TA=25C on PCB), -11.4A (TC=25C on heatsink). RDS(on) = 19.5mOhm typical \/ 24mOhm maximum at VGS=-10V, ID=-9.1A; 28mOhm typical \/ 35mOhm maximum at VGS=-4.5V, ID=-6.9A. Gate threshold voltage: -1.0V to -3.0V at ID=-250uA. Total gate charge: 15nC typical at VGS=-4.5V, 32nC at VGS=-10V. Input capacitance: 1350pF. Forward transconductance: 23S. Body diode forward voltage: -0.75V typical at IS=-2A. Body diode reverse recovery: 34ns \/ 22nC typical. Power dissipation: 2.5W (TA=25C on PCB), 5.0W (TC=25C). Thermal resistance: RthJA = 50C\/W max, RthJF = 25C\/W max. Switching times at VGS=-10V: td(on)=10ns, tr=8ns, td(off)=45ns, tf=12ns typical. Operating junction temperature: -55C to +150C. Single-pulse avalanche: 20mJ \/ 20A. The -T1-GE3 suffix indicates: T1 = tape and reel (2500 units), GE3 = lead-free and halogen-free. Active product, RoHS compliant, EAR99.<\/p>","protected":false},"excerpt":{"rendered":"
The SI4435DDY-T1-GE3 from Vishay Siliconix is a P-Channel 30-V (D-S) TrenchFET power MOSFET in an 8-pin SOIC (SO-8) package (4.88 x 3.89 x 1.54 mm). It is halogen-free per IEC 61249-2-21 and RoHS compliant. Key specifications: VDS = -30V, VGS = plus\/minus 20V, ID = -8.1A (TA=25C on PCB), -11.4A (TC=25C on heatsink). RDS(on) = […]<\/p>\n","protected":false},"author":2,"featured_media":2837,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[13,56],"tags":[],"chip_brand":[136],"class_list":["post-1928","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-integrated-circuits-ics","category-mosfets","chip_brand-vishay"],"acf":{"brief_explanation":"P-ch MOSFET, -30V, -8.1A, 24mOhm RDS(on)@-10V, TrenchFET, SOIC-8, halogen-free, -55~150C","date_code":"","package_case":"SOIC-8 (SO-8, 150mil) (4.88 x 3.89 x 1.54 mm, 1.27mm pitch)","in_stock":38787,"datasheet":"https:\/\/www.vishay.com\/mosfets\/list\/product-68841\/","price":"$0.31 (1K+ pcs)","product_introduction":"The SI4435DDY-T1-GE3 from Vishay Siliconix is a P-channel enhancement-mode TrenchFET power MOSFET rated for -30V drain-source voltage and -8.1A continuous drain current in an SOIC-8 (SO-8) surface-mount package. It is one of the most popular P-channel MOSFETs for load switching and battery management applications, offering an excellent balance of low on-resistance, moderate gate charge, and wide availability.\n\nThe TrenchFET technology uses a vertical trench gate structure that significantly reduces the channel resistance compared to planar MOSFET architectures. By etching deep trenches into the silicon and lining them with the gate oxide and gate electrode, the channel is formed on the vertical sidewalls of the trench. This increases the channel width per unit area, reducing the specific on-resistance (RDS(on) x area) and enabling lower RDS(on) in a smaller die. The SI4435DDY achieves 24mOhm maximum RDS(on) at VGS=-10V in a standard SO-8 package, making it suitable for load switching applications where voltage drop and power dissipation must be minimized.\n\nThe SO-8 (150mil) package is the industry-standard footprint for medium-power surface-mount MOSFETs. It features a gull-wing lead configuration with three source pins (1-3), one gate pin (4), and four drain pins (5-8) connected to the die attach pad for thermal dissipation. The multiple source and drain pins reduce package parasitic inductance and provide parallel current paths, improving current handling and thermal performance. The LITTLE FOOT designation indicates that this package has been modified to provide the heat transfer capabilities required by power devices.\n\nAs a P-channel MOSFET, the SI4435DDY is turned on by applying a negative gate-source voltage (VGS < 0). For a high-side load switch application with a 5V supply, the gate is pulled to GND (VGS = -5V) to turn on the MOSFET, connecting the source (connected to 5V supply) to the drain (connected to the load). When the gate is pulled to the source voltage (VGS = 0V), the MOSFET turns off, disconnecting the load. This simple high-side switching configuration is the primary use case for P-channel MOSFETs, as it avoids the need for a gate drive voltage above the supply rail that N-channel high-side switches require.\n\nThe RDS(on) specification varies significantly with gate drive voltage. At VGS=-10V, the maximum RDS(on) is 24mOhm, while at VGS=-4.5V, it increases to 35mOhm. For a 5V system where the gate can be driven to GND (VGS=-5V), the RDS(on) falls between these values, typically around 28-30mOhm. This voltage-dependent RDS(on) must be considered in thermal calculations, as higher RDS(on) leads to more power dissipation at the same load current.\n\nThe gate charge of 15nC at VGS=-4.5V and 32nC at VGS=-10V determines the switching energy and the gate drive current required for a given switching frequency. For load switching applications where the MOSFET switches infrequently (e.g., power-on\/off), the gate charge has minimal impact on power dissipation. For PWM applications at higher frequencies, the gate charge must be considered in the total power budget.\n\nThe body diode (inherent in all MOSFETs) has a forward voltage of 0.75V typical at 2A and a reverse recovery time of 34ns. This body diode can conduct current when VDS is negative (drain below source), which is the normal forward direction for a P-channel MOSFET. In load switching applications, the body diode may briefly conduct during transients before the MOSFET channel fully enhances.\n\nThe -T1-GE3 suffix provides important ordering information: T1 indicates tape-and-reel packaging (2,500 units per reel), and GE3 indicates both lead-free (per RoHS) and halogen-free (per IEC 61249-2-21). The -E3 suffix (SI4435DDY-T1-E3) is lead-free but not halogen-free. The GE3 variant is preferred for environmentally sensitive applications and regions with strict halogen-free requirements.","working_principle":"The SI4435DDY-T1-GE3 operates as a P-channel enhancement-mode MOSFET using TrenchFET vertical structure technology.\n\nTrenchFET Structure: Unlike planar MOSFETs where the channel is formed on the silicon surface, the TrenchFET uses deep reactive-ion-etched trenches filled with gate polysilicon. The P-body and N+ source regions are formed on the sidewalls of these trenches. When a negative voltage is applied to the gate (relative to the source), an inversion layer (N-type channel) forms along the trench sidewalls, connecting the N+ source to the N- drain epitaxial layer. This vertical current flow path is much shorter than the lateral path in planar devices, reducing the channel resistance. Additionally, the trench structure allows a much higher channel density (channel width per unit die area), which directly reduces the specific on-resistance.\n\nP-Channel Operation: As a P-channel MOSFET, the SI4435DDY has a P+ substrate (drain), P- epitaxial layer (drift region), N-body (channel region), and P+ source diffusion. The gate oxide and gate electrode are formed on the trench sidewalls. When VGS = 0V (gate shorted to source), no inversion layer forms and the device is in the off state. When a negative voltage is applied to the gate (VGS < threshold voltage, approximately -1.0 to -3.0V), an inversion layer of holes forms along the trench sidewalls, creating a conductive P-type channel from source to drain. Current flows from source to drain (conventional current direction) when the drain is at a lower potential than the source.\n\nOn-Resistance Components: The total RDS(on) consists of several resistive components: (1) Channel resistance (Rch) - the resistance of the inversion layer in the trench; (2) Accumulation resistance (Racc) - the resistance at the transition from the channel to the drift region; (3) Drift region resistance (Rd) - the resistance of the P- epitaxial layer between the channel and the P+ substrate; (4) Substrate resistance (Rsub) - the resistance of the P+ substrate; (5) Package resistance (Rpkg) - the resistance of the die attach, lead frame, and solder joints. The TrenchFET structure primarily reduces Rch and Racc compared to planar devices, while Rd and Rsub become the dominant components at lower voltage ratings.\n\nGate Charge and Switching: The gate charge (Qg) represents the total charge that must be supplied to the gate to switch the MOSFET from off to on (or vice versa). The gate charge consists of three regions: (1) Qgs (gate-source charge) - charges the gate-source capacitance until the threshold voltage is reached; (2) Qgd (gate-drain charge, also called Miller charge) - during this plateau region, the drain voltage falls while the gate voltage remains relatively constant; (3) Additional charge to reach the final gate voltage. The Qgd of 7.5nC is particularly important because it determines the switching time during the Miller plateau, where the drain voltage transitions. The gate resistance of 5.8 ohms (internal) combines with the external gate resistor to determine the RC time constant for gate charging.\n\nBody Diode: The inherent body diode is formed by the P-N junction between the N-body and the P-epitaxial\/P+ substrate. This diode is forward-biased when the drain voltage is below the source voltage (VDS > 0 for P-channel, since both VDS and ID are negative in normal operation). The body diode has a forward voltage of 0.75V typical at 2A and can carry continuous current up to 4.1A (TC=25C). The reverse recovery time of 34ns and reverse recovery charge of 22nC are relevant for freewheeling applications where the body diode conducts during each switching cycle.\n\nAvalanche Rating: The device is rated for single-pulse avalanche energy of 20mJ and avalanche current of 20A. Avalanche occurs when the drain-source voltage exceeds the breakdown voltage (-30V), typically during inductive load switching. The avalanche rating indicates the maximum energy the device can absorb in a single event without damage. This is important for unclamped inductive switching applications where voltage spikes may exceed the rated VDS.","pin_description":"
| Pin<\/th> | Name<\/th> | Type<\/th> | Description<\/th><\/tr><\/thead> | ||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1<\/td> | S<\/td> | Source<\/td> | MOSFET source terminal; connect to the higher-potential side of the power rail (e.g., battery positive or VCC rail in high-side switch configuration); internally connected to pins 2 and 3; three source pins reduce package inductance and current density per bond wire; connect all three source pins to the source net on PCB<\/td><\/tr> | ||||||||||||||||||||||||||||||||||||
| 2<\/td> | S<\/td> | Source<\/td> | MOSFET source terminal; internally connected to pins 1 and 3<\/td><\/tr> | ||||||||||||||||||||||||||||||||||||
| 3<\/td> | S<\/td> | Source<\/td> | MOSFET source terminal; internally connected to pins 1 and 2<\/td><\/tr> | ||||||||||||||||||||||||||||||||||||
| 4<\/td> | G<\/td> | Gate<\/td> | MOSFET gate terminal; controls the on\/off state of the MOSFET; apply negative voltage relative to source (VGS < -1.0V) to turn on; VGS = 0V to turn off; maximum VGS = plus\/minus 20V; gate input capacitance ~1350pF; typical gate resistance 5.8 ohms; drive with low-impedance gate driver for fast switching; add series gate resistor (1-10 ohm) to control dv\/dt and reduce EMI<\/td><\/tr> | ||||||||||||||||||||||||||||||||||||
| 5<\/td> | D<\/td> | Drain<\/td> | MOSFET drain terminal; connect to the load side in high-side switch configuration; internally connected to pins 6, 7, and 8 through the die attach pad; four drain pins provide low-inductance current path and thermal connection to PCB; the drain is also the cathode of the body diode<\/td><\/tr> | ||||||||||||||||||||||||||||||||||||
| 6<\/td> | D<\/td> | Drain<\/td> | MOSFET drain terminal; internally connected to pins 5, 7, and 8<\/td><\/tr> | ||||||||||||||||||||||||||||||||||||
| 7<\/td> | D<\/td> | Drain<\/td> | MOSFET drain terminal; internally connected to pins 5, 6, and 8<\/td><\/tr> | ||||||||||||||||||||||||||||||||||||
| 8<\/td> | D<\/td> | Drain<\/td> | MOSFET drain terminal; internally connected to pins 5, 6, and 7<\/td><\/tr><\/tbody><\/table>","application_scenarios":"
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