BSP129H6906XTSA1 - 240V N-Ch Depletion MOSFET | Infineon
MPN: BSP129H6906XTSA1 ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $1.42 | $1.42 |
| 10 | $1.21 | $12.10 |
| 100 | $0.95 | $95.00 |
| 500 | $0.78 | $390.00 |
| 1,000 | $0.65 | $650.00 |
Drop-in alternatives for BSP129H6906XTSA1 — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
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View Datasheet →BSP129H6906XTSA1 Maximum Ratings & Electrical Characteristics
| Manufacturer | Infineon Technologies |
| Part Number | BSP129H6906XTSA1 |
| FET Type | N-Channel, Depletion Mode |
| Drain-Source Voltage (VDS) | 240 V |
| Continuous Drain Current (ID) at TA=25C | 350 mA |
| Power Dissipation (PD) at TA=25C | 1.8 W |
| Drain-Source On-Resistance (RDS(on)) | 6 Ohm (max) |
| Operating Mode | Normally-On (Depletion) |
| Package | PG-SOT223-4 (SOT-223) |
| Mounting Type | Surface Mount |
| Number of Pins | 3 functional + 1 tab (4 leads) |
| ESD Protection | Integrated Zener diodes on gate |
| RoHS Status | Compliant |
| MSL Level | 1 (unlimited floor life) |
BSP129H6906XTSA1 Pin Configuration
| Pin 1 | Gate (G) — Gate control input; drive below pinch-off voltage (~-3 V) to turn off |
| Pin 2 | Drain (D) — Drain terminal; internally bonded to the metal tab |
| Pin 3 | Source (S) — Source terminal; reference for VGS bias |
| Pin 4 | Drain Tab — Metal tab electrically tied to pin 2 (Drain); provides thermal dissipation path |
BSP129 Safe Operating Area (DC)
Typical Applications
BSP129H6906XTSA1 is suitable for 6 applications: Power-Supply Startup Power, Over-Voltage Protection Clamp, Inrush-Current Limiter, Off-Line Voltage Reference, Constant-Current Source, Fail-Safe High-Side Switch.
Power-Supply Startup Power
The BSP129H6906XTSA1's depletion-mode normally-on behavior makes it a natural choice for offline power-supply startup bias circuits, where it conducts during the initial mains connection to charge a bulk capacitor before the auxiliary winding takes over. With 240 V VDS, the device tolerates rectified 120/230 VAC rails directly, and the 350 mA ID rating supplies the bootstrap current required by modern PWM controllers. Place the BSP129 between the rectified rail and a small current-limiting resistor, with its gate held at 0 V until the auxiliary supply asserts a negative bias to switch it off. Compared to a startup resistor, the depletion MOSFET reduces standby power by 10x while still providing surge current to the controller.
Recommended
Over-Voltage Protection Clamp
The BSP129H6906XTSA1 serves as a robust over-voltage protection clamp in industrial 24 V and 48 V bus systems, where its 240 V VDS rating provides 5-10x headroom against transient surges. In a typical application, the depletion MOSFET sits between the bus and the downstream load; during normal operation, VGS = 0 keeps it conducting with only 6 Ohms of on-resistance loss. When an over-voltage event exceeds the gate-source Zener breakdown of the auxiliary clamp circuit, the BSP129 is rapidly pinched off, disconnecting the load in microseconds. Designers favor this topology because the device defaults to conducting, ensuring no brownout under normal conditions.
Recommended
Inrush-Current Limiter
The BSP129H6906XTSA1 implements an elegant inrush-current limiter by exploiting its depletion-mode behavior: at VGS = 0 the device conducts with 6 Ohms RDS(on), limiting the initial charging current into large bulk capacitors. As the output voltage rises, a sense resistor or auxiliary circuit pulls VGS negative, gradually reducing conduction until full cut-off. This self-regulating behavior eliminates the need for an external current-sense amplifier. With 350 mA continuous ID and 240 V VDS, the BSP129 handles inrush limiting for both 24 V industrial buses and 48 V telecom rails, replacing traditional NTC thermistors with a solid-state solution that recovers instantly after each power cycle.
Recommended
Off-Line Voltage Reference
The BSP129H6906XTSA1 is uniquely suited to off-line voltage reference circuits where a stable bias must be generated directly from the rectified mains without any auxiliary power. Its depletion-mode architecture ensures conduction from the moment the input is energized, charging a reference capacitor to a Zener-clamped voltage. The 240 V VDS rating survives rectified 120 VAC or 230 VAC directly, and the 350 mA ID supplies the small bias currents needed by downstream opto-couplers or error amplifiers. This eliminates the auxiliary winding on the main transformer, reducing BOM cost by 5-10% in low-power isolated converters.
Recommended
Constant-Current Source
The BSP129H6906XTSA1 forms a simple two-terminal constant-current source when biased with a source resistor: VGS = -ID * RS, stabilizing the drain current at approximately IDSS * (1 - VGS/VGS(off))^2. With IDSS around 350 mA and a typical VGS(off) of -3 V, a 10 Ohm source resistor sets Iout near 250 mA with excellent line regulation. The 240 V VDS allows the source to operate from rails up to 200 V, making it ideal for LED drivers, bias networks, and analog signal conditioning. Compared to a discrete BJT constant-current source, the depletion MOSFET offers superior thermal stability and lower minimum headroom.
Recommended
Fail-Safe High-Side Switch
The BSP129H6906XTSA1 enables a true fail-safe high-side switch that defaults to ON at power-up — critical for safety-relevant loads such as emergency lighting, alarm systems, and motor hold circuits. By placing the depletion MOSFET on the high side and using a small auxiliary rail to generate a negative VGS bias only when the load should be disconnected, the design guarantees that the load is energized before any microcontroller or supervisory logic is active. With 240 V VDS, 350 mA ID, and the rugged SOT-223 package, the BSP129 delivers drop-in robustness that would otherwise require a discrete BJT/MOSFET combination. Designers value the part for IEC 61508 SIL-2 capable safety paths.
Recommended
Recommended Products Summary
Engineering reference data for BSP129H6906XTSA1 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | BSP129H6327XTSA1 | BSP135H6327XTSA1 | BSP135H6906XTSA1 | BSS127H6327XTSA2 | BSD214SNH6327XTSA1 |
|---|---|---|---|---|---|---|
| Brand | Infineon Technologies | Infineon Technologies | Infineon Technologies | Infineon Technologies | Infineon Technologies | Infineon Technologies |
| Package | PG-SOT223-4 (SOT-223) | PG-SOT223-4 (SOT-223) - same | PG-SOT223-4 (SOT-223) - same | PG-SOT223-4 (SOT-223) - same | PG-SOT223-4 (SOT-223) - same | PG-SOT223-4 (SOT-223) - same |
| FET Type | N-Channel Depletion | N-Channel Depletion | N-Channel Depletion | N-Channel Depletion | N-Channel Enhancement | P-Channel Enhancement |
| Drain-Source Voltage (VDS) | 240 V | 240 V | 600 V | 600 V | 600 V | 20 V |
| Continuous Drain Current (ID) | 350 mA | 350 mA | 100 mA | 100 mA | 100 mA | 1.4 A |
| On-Resistance (RDS(on)) | 6 Ohm max | 6 Ohm max | 20 Ohm max | 20 Ohm max | 20 Ohm max | 0.13 Ohm max |
| Power Dissipation (PD) | 1.8 W | 1.8 W | 1.8 W | 1.8 W | 1.8 W | 1.8 W |
| Operating Mode | Normally-On (Depletion) | Normally-On (Depletion) | Normally-On (Depletion) | Normally-On (Depletion) | Normally-Off (Enhancement) | Normally-Off (Enhancement) |
| Unit Price (qty 1, USD) | 1.42 | 1.42 | 1.10 | 1.10 | 0.95 | 0.85 |
Key Differentiators
- 240 V VDS rating in SOT-223 (vs BSP135H6327XTSA1)
- True normally-on depletion behavior (vs BSS127H6327XTSA2)
- H6906 reel suffix matches high-volume assembly lines (vs BSP129H6327XTSA1)
Design Notes
At ID = 350 mA continuous and RDS(on) of 6 Ohm, the BSP129H6906XTSA1 dissipates approximately 0.74 W. The SOT-223 package has a thermal resistance of about 80 C/W on a 1 oz copper pour, producing a 60 C junction temperature rise above ambient. For continuous operation near 350 mA in environments above 65 C, expand the drain-tab copper area to at least 400 mm^2 or attach a small clip-on heatsink. Derate ID linearly to zero at TA = 125 C. Estimated: based on standard JEDEC SOT-223 thermal test board (1 oz, 1 in^2 copper).
The SOT-223 drain tab is the dominant thermal path. Use a thermal via array (typically 4-9 vias of 0.3 mm diameter) under the tab to conduct heat into an inner copper plane. Stitch the top, inner, and bottom copper with multiple vias to spread heat laterally. Avoid routing sensitive analog signals under the drain tab to prevent coupling. Place the gate-bias resistor divider within 5 mm of pin 1 to minimize noise injection.
A common mistake is treating the BSP129 like an enhancement-mode MOSFET and assuming it is OFF at VGS = 0 V. In reality, it is fully ON and will pass 350 mA if the gate is left floating or tied to source. Always actively bias the gate — either at 0 V for full conduction, or below VGS(off) (typically -2.5 V to -3.5 V) for cutoff. Leaving the gate floating can cause unpredictable behavior due to leakage currents. Also, do not exceed the 240 V VDS rating; transient overshoot from inductive loads requires a snubber or TVS clamp.
Keep the high-voltage drain trace on the top layer as short as possible to minimize parasitic inductance. For off-line applications, maintain at least 3 mm clearance between drain traces and any low-voltage signal routing to meet IEC 60950 / IEC 62368 creepage requirements. Place input filter capacitors close to the source pin to localize the switching current loop. The gate trace should be guarded by ground copper to prevent dv/dt-induced turn-on in noisy environments.
Compliance Information
RoHS and REACH compliant per Infineon product page. Not AEC-Q100 qualified; for automotive applications, refer to Infineon's automotive-grade depletion MOSFET portfolio. Halogen-free and lead-free confirmed.
