Infineon Technologies IRF3709ZS

Overview

IRF3709ZS from Infineon Technologies is an N-channel enhancement-mode HEXFET Power MOSFET in TO-220AB package, designed as a low-side synchronous rectifier in high-frequency DC/DC converters. It delivers 6.3 mΩ R_DS(on) at V_GS = 4.5 V, 17 nC total gate charge, and 30 V V_DSS, enabling efficient operation in computer processor power supplies with tight thermal constraints.

For engineers reviewing the IRF3709ZS datasheet, IRF3709ZS pinout, IRF3709ZS application, or IRF3709ZS equivalent, key selection criteria include its low R_DS(on) at 4.5 V drive, fully characterized avalanche capability, body diode reverse recovery performance (Q_rr = 6.2–9.3 nC), and thermal resistance (R_θJC = 1.89 °C/W) for PCB-mounted thermal management.

Technical Context

This MOSFET operates in enhancement mode with a gate threshold voltage of 1.35–2.25 V and exhibits strong temperature stability: R_DS(on) increases only ~1.8× from 25°C to 175°C (Fig. 4), while V_GS(th) decreases linearly at −5.5 mV/°C (Fig. 10). Its low Q_gd/Q_gs1 ratio minimizes C_dv/dt turn-on risk in high-dV/dt synchronous buck nodes.

The device supports clamped inductive switching with single-pulse avalanche energy up to 250 mJ at I_AS = 5.4 A (Fig. 16), and features a robust body diode with t_rr = 16–24 ns and V_SD ≤ 1.0 V at I_S = 17 A (Fig. 7), critical for minimizing shoot-through and conduction loss in synchronous rectification.

Key Specifications

Pinout & Package

IRF3709ZS uses the standard TO-220AB package with isolated tab (drain-connected), suitable for through-hole PCB mounting and mechanical heatsinking. Pin assignment follows industry-standard three-terminal configuration.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar N-channel power MOSFET applications.

Compared with IRF3709ZS, IRL3713PbF offers marginally better conduction efficiency but less ruggedness under inductive fault conditions, while SI7850DP-T1-GE3 trades gate drive simplicity and thermal mounting flexibility for smaller footprint and higher switching loss.

Availability

IRF3709ZS is available at Aetrix Electronics and suitable for server CPU voltage regulators, laptop core power supplies, and industrial PLC I/O modules requiring stable component supply and long-term manufacturability.

Supply support for IRF3709ZS includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Infineon Technologies is a German semiconductor manufacturer specializing in power management, automotive, and industrial control ICs and discrete devices.

The HEXFET Power MOSFET product line targets high-efficiency, high-reliability power conversion in computing, telecom, and industrial applications, with emphasis on low gate charge, avalanche robustness, and thermal performance.

FAQ

Is IRF3709ZS suitable for 3.3 V gate drive?

No - IRF3709ZS is not guaranteed to fully enhance at 3.3 V. Its gate threshold voltage ranges from 1.35 V to 2.25 V, but R_DS(on) is specified only at V_GS ≥ 4.5 V (6.3 mΩ max). At 3.3 V, R_DS(on) rises significantly (>15 mΩ), increasing conduction loss and thermal stress. Use only with ≥4.5 V gate drive for rated performance.

What is the maximum continuous drain current at 85°C case temperature?

At T_C = 85°C, the maximum continuous drain current is approximately 72 A. This is derived from linear derating: 87 A at 25°C minus (85 − 25) × 0.53 A/°C = 87 − 31.8 = 55.2 A - however, the datasheet specifies 79 A at 25°C and 62 A at 100°C, indicating a derating slope of (79−62)/(100−25) = 0.227 A/°C. Thus at 85°C: 79 − (85−25)×0.227 ≈ 65 A. Conservative design uses 62 A per datasheet limit at 100°C.

Can IRF3709ZS replace IRF3709Z in existing designs?

Yes - IRF3709ZS and IRF3709Z share identical electrical specifications, thermal ratings, and TO-220AB package dimensions. The "S" suffix denotes tape-and-reel packaging for automated assembly, while "Z" indicates tube packaging. No circuit or layout changes are required for substitution; only handling and placement logistics differ.

Does IRF3709ZS require a gate resistor for stability?

Yes - a gate resistor (typically 5–22 Ω) is recommended to dampen ringing caused by gate loop inductance and MOSFET input capacitance (C_iss = 2130 pF). Without it, fast edge rates (t_r = 41 ns) can excite parasitic oscillations, increasing EMI and risking spurious turn-on. The resistor also controls dV/dt during switching and protects the gate driver from peak current surges.