IRLML6402TRPBF - -20V P-Channel HEXFET Power MOSFET from Infineon

What Is IRLML6402TRPBF and How Does It Work?

It is a P-Channel enhancement-mode MOSFET on Infineon's HEXFET process. With a P-Channel, current flows from Source to Drain when the Gate is pulled negative relative to the Source. Pull Gate low → MOSFET ON. Pull Gate to Source voltage → MOSFET OFF. That makes it natural for high-side switching: connect Source to your power rail, Drain to the load, and a simple GPIO (or a pull-up resistor) controls the Gate. No charge pump, no bootstrap - just a wire.

The IRLML6402TRPBF stands out for its low gate charge (8 nC typical) and low threshold voltage (0.4V–1.2V). You can drive it from 1.8V logic in a pinch, though R_DS(on) climbs to about 120mΩ at that voltage. At 3.3V or 5V gate drive, it saturates fully.

Position in the product line: Mid-range P-Channel. 65mΩ is competitive for SOT-23 P-FETs, but newer parts like DMG2305UX-7 (52mΩ) have since surpassed it. The real value of this part is its widespread ecosystem - it is designed into thousands of existing products, which means replacement and repair demand is steady.

What Are the Specifications of IRLML6402TRPBF?

Thermal reality check: 1.3W max at 25°C. With 3.7A through 65mΩ, conduction loss alone is I²R = 0.89W - already 68% of the budget before you add switching losses. In practice, treat this as a 1.5A–2A continuous part unless you have aggressive copper pour on the drain pin.

Key parameter commentary:

• R_DS(on) = 65mΩ @ V_gs = -4.5V: This is the headline number. For a P-Channel in SOT-23, 65mΩ is solid. At 3.7A, I²R = 0.89W which exceeds 1.3W practically - the 3.7A rating is a pulsed maximum.
• V_gs(th) spread (-0.4V to -1.2V): Production tolerance is wide. At the high end (1.2V), a 1.8V signal still turns it on with 0.6V margin. At the low end (0.4V), the MOSFET may leak at V_gs = 0V if the Gate is left floating - always use a pull-up resistor to Source.
• Q_g = 8 nC: Low enough for direct GPIO drive below 100 kHz. At 100 kHz, gate drive power is P = Q_g × V_g × f = 8nC × 5V × 100k = 4 mW - negligible.
• C_iss = 633 pF: Low input capacitance means fast switching. Datasheet typical turn-on delay is 6 ns and rise time is 3 ns at V_gs = -4.5V.

Pinout (SOT-23)

   (TOP VIEW)

       D
       |
   G-| |-S

   Pin 1: Gate (G)
   Pin 2: Source (S)
   Pin 3: Drain (D)

Standard SOT-23 pinout - same as AO3419, DMG2305UX-7, and most SOT-23 P-FETs.

What Is IRLML6402TRPBF Used For?

Battery Protection Circuits (Mobile / Wearable)

The -20V V_ds and 3.7A rating make it a common choice for single-cell Li-ion battery protection in smartphones, tablets, and wearables. The low R_DS(on) minimizes voltage drop in the discharge path - at 500mA load, the drop is just 500mA × 65mΩ = 32.5mV. The SOT-23 package fits the tight PCB real estate.

Key parameter: R_DS(on) at V_gs = -2.5V - battery protection ICs often drive the Gate at battery voltage (3.0-4.2V). At V_gs = -3.7V, typical R_DS(on) drops to ~60mΩ, which is acceptable.

Load Switch for Portable Electronics

High-side load switch to disconnect battery-powered sub-circuits in standby. P-Channel is convenient here: Source to power rail, Drain to load, logic-low on Gate turns the load ON. No charge pump needed.

Key parameter: V_gs(th) must be low enough for the logic voltage available. At V_gs = -1.8V, R_DS(on) is ~120mΩ - still usable for loads up to 500mA with acceptable drop.

DC-DC Converter Startup and Sequencing

Inrush current limiter or power sequencing switch in multi-rail systems. The Gate can be controlled by a power sequencing IC or RC delay to ensure rails come up in the correct order.

Key parameter: The Gate RC time constant is determined by C_iss = 633 pF. A 10kΩ pull-up gives τ = 6.3 µs ramp time.

PCMCIA / CF Card Power Switching

Historically used for PCMCIA slot power management where both 3.3V and 5V rails need independent switching. The low R_DS(on) keeps voltage drop within PCMCIA specification limits.

Small Motor / Actuator Drive

For small DC motors or solenoids under 500mA, the IRLML6402TRPBF can be used as a low-frequency PWM switch. The 8nC gate charge allows direct PWM from a microcontroller at up to 20–50 kHz.

IRLML6402TRPBF Cross-Reference and Alternatives

Important: Infineon has classified this part as NRND (Not Recommended for New Designs). The alternatives below are pin-compatible in SOT-23.

Pin-Compatible Direct Replacements (SOT-23)

Quick selection guide:

• Conservative drop-in: AO3419 - same specs, mature product, everywhere.
• Best upgrade: DMG2305UX-7 - 52mΩ vs 65mΩ, 4.2A vs 3.7A, similar price. No reason to stay on the original.
• Budget (high volume): VB2290 or BL3435 - worth qualifying if you buy reels.

NOT Compatible

How to Verify Genuine IRLML6402TRPBF?

Markings: Genuine Infineon/IR parts have clear, consistent laser marking. The top code is typically "642" or "IRLML6402" depending on batch. Counterfeits often have blurry or misaligned printing.

R_DS(on) test (most reliable): Apply V_gs = -4.5V, pass 1A through drain-source, read voltage drop. Calculate R = V/I. Genuine parts measure ≤ 65 mΩ. Counterfeits often measure 100–200 mΩ or higher.

V_gs(th) distribution: Sample 5–10 parts from the same batch. Genuine parts should have V_gs(th) within 100mV of each other. A spread of 300mV+ or all clustering at the spec limit suggests a counterfeit.

Package inspection: Genuine SOT-23 has consistent mold flash, flat leads with proper co-planarity, and a smooth epoxy surface. Rough edges, uneven mold lines, or oxidized leads are red flags.

Source traceability: At ICMASS, all Infineon parts are sourced from authorized distribution channels with full traceability documentation including date codes and lot numbers available on request.

Frequently Asked Questions About IRLML6402TRPBF

Q1: IRLML6402TRPBF stays ON all the time - what could be wrong?

A: The most common cause is the Gate not being pulled high enough to turn the MOSFET OFF. For a P-Channel, the Gate must be at or above the Source voltage to ensure it is fully OFF. If you are driving it with an open-drain GPIO, the pull-up resistor must pull the Gate all the way to the Source rail. A second common cause is reversed Source/Drain connections - the body diode will conduct. Pinout: Pin 1 = Gate, Pin 2 = Source, Pin 3 = Drain.

Q2: Does IRLML6402TRPBF work with 1.8V logic?

A: Yes, with caveats. V_gs(th) is -0.4V to -1.2V. At V_gs = -1.8V, typical R_DS(on) is around 120mΩ - about double the 4.5V value. This is acceptable for loads under 500mA. Check that your 1.8V GPIO has sufficient drive strength for the 8nC gate charge; weak drive will cause slow switching and increased losses.

Q3: IRLML6402TRPBF vs IRLML6402PBF - what is the difference?

A: The IRLML6402PBF is the same die in tube (stick) packing instead of tape-and-reel. The "TR" in IRLML6402TRPBF stands for Tape-and-Reel. Electrically and mechanically identical.

Q4: Is IRLML6402TRPBF obsolete? Can I still buy it?

A: Infineon has classified it as NRND (Not Recommended for New Designs), but it is not fully obsolete. ICMASS maintains stock while inventory lasts. For new designs, we recommend qualifying AO3419 or DMG2305UX-7 as drop-in replacements.

Q5: IRLML6402TRPBF gets hot in my circuit - what should I check?

A: First, verify you are not exceeding the 1.3W limit. At 3.7A, conduction loss alone is 0.89W. Check actual load current - above 1A continuous in 25°C ambient, the part will be warm (~40-50°C). If too hot to touch (>70°C), you need better PCB copper heatsinking, a lower R_DS(on) alternative, or cooling. Also verify V_gs: at lower V_gs, R_DS(on) increases significantly.

Q6: Can I use IRLML6402TRPBF with a 12V supply?

A: V_ds max is -20V so it can handle 12V. However, V_gs max is ±12V - do not exceed this. At V_gs = -12V you achieve the lowest R_DS(on), but check the SOA derating at higher V_ds - you cannot run full rated current at 12V.

Q7: How do I properly drive IRLML6402TRPBF from a 3.3V MCU?

A: Connect Source to 3.3V, Drain to load, Gate to GPIO through a 1–10kΩ resistor. GPIO LOW (0V) → V_gs = -3.3V → MOSFET ON. GPIO HIGH (3.3V) → V_gs = 0V → MOSFET OFF. Add a 10kΩ pull-up from Gate to Source to ensure the MOSFET stays OFF during MCU boot.

Q8: Can I parallel multiple IRLML6402TRPBF to increase current capacity?

A: Yes. The positive temperature coefficient of R_DS(on) promotes current sharing. Each MOSFET needs its own gate resistor (10Ω typical) to prevent oscillation. Derate total current by about 20% for thermal mismatch.

Q9: Is there an automotive-grade version of IRLML6402TRPBF?

A: The standard IRLML6402TRPBF is not AEC-Q101 qualified. For automotive P-Channel SOT-23 MOSFETs, consider DMG2305UX-7Q from Diodes Inc or consult Infineon's automotive MOSFET portfolio.

Q10: What is the avalanche rating?

A: Single-pulse avalanche energy (EAS) is approximately 100 mJ at I_d = 3.7A and L = 1mH. Repetitive avalanche should be avoided - if your circuit subjects the MOSFET to repetitive avalanche events (e.g., motor drive without proper freewheeling), the junction temperature will rise and eventually damage the part. Always use a freewheeling diode across inductive loads.

Q11: IRLML6402TRPBF seems to conduct with V_gs = 0V, why?

A: If the MOSFET conducts when V_gs = 0V, either the Gate is floating (open) and picking up noise, or the part is damaged (gate oxide breakdown). A floating Gate can couple stray electric fields and create enough V_gs to partially turn on the MOSFET. Always use a pull-up resistor (10kΩ typical) between Gate and Source.

Q12: What is the recovery time of the body diode?

A: Typical reverse recovery time (t_rr) is approximately 20–30 ns at I_F = 3.7A and di/dt = 100 A/µs. This is relatively fast. For high-frequency (>100 kHz) inductive loads, an external Schottky in parallel is recommended to reduce reverse recovery losses.

Pricing & Availability

Stock: Infineon IRLML6402TRPBF and pin-compatible alternatives (AO3419, DMG2305UX-7) available for immediate shipment.

Lead time: 3-5 business days for small quantities. Reel orders ship within 1 week.