onsemi FDN304PZ P-Channel MOSFET: Datasheet, Application Circuit, and Replacement Guide

The onsemi FDN304PZ is a popular P-Channel enhancement mode field effect transistor (FET) housed in a compact Space-Saving SC-75/SOT-416 package. It is designed for low-voltage, high-speed switching applications, making it a common choice for power management tasks in portable and battery-operated electronics.

This article provides a detailed overview of its key specifications, a typical application circuit, and guidance for finding a suitable replacement.

Datasheet Overview and Key Specifications

The FDN304PZ is characterized by its low threshold voltage and low on-resistance, which are critical for minimizing power loss and improving efficiency. Here are some of its most important electrical parameters:

Drain-Source Voltage (V_DS): -20 V

Continuous Drain Current (I_D): -1.7 A

On-Resistance (R_DS(on)): Typically 70 mΩ at V_GS = -4.5 V

Gate Threshold Voltage (V_GS(th)): -0.7 V to -1.5 V (ensures easy drive from low-voltage logic)

Package: SC-75 / SOT-416 (Ultra-small form factor for high-density PCB design)

These specs make it ideal for applications such as:

Load Switching in smartphones, tablets, and wearables.

Power Management in battery-powered devices.

DC-DC Converters and power distribution circuits.

Motor Control for small motors.

Typical Application Circuit: Load Switch

A fundamental use case for the FDN304PZ is a high-side load switch. This circuit controls power to a specific section of a board (the load).

Circuit Operation:

1. Microcontroller (MCU) provides the control signal.

2. When the MCU output is LOW (0V), the voltage at the gate (G) is lower than the source (S), which is connected to the battery voltage (e.g., 3.7V). This turns the P-Channel MOSFET ON, allowing current to flow from the source to the drain (D) and power the load.

3. When the MCU output is HIGH (e.g., 3.3V), the gate-to-source voltage (V_GS) approaches 0V. This turns the MOSFET OFF, disconnecting power from the load.

The pull-up resistor (R1, e.g., 100kΩ) ensures the MOSFET remains off if the MCU pin is in a high-impedance state (e.g., during startup).

Replacement Guide

Finding a replacement for the FDN304PZ requires careful cross-referencing of key parameters to ensure compatibility and performance.

1. Key Parameters to Match:

Type: Must be a P-Channel MOSFET.

V_DS: The absolute maximum voltage rating should be at least -20V.

I_D: The continuous drain current should be -1.7A or higher.

R_DS(on): Look for a similar or lower value (e.g., < 70 mΩ) at a similar gate drive voltage (V_GS = -4.5V).

Package: The SOT-416 (SC-75) package is crucial for physical fitment on the PCB.

2. Potential Direct Replacements/Alternatives:

DMG3415U-7 (Diodes Incorporated)

SI2301BDS (Vishay)

ZXMP6A17GTA (Diodes Incorporated)

AO3401 (Alpha & Omega Semiconductor) - Note: Check V_DS and package.

Always consult the latest datasheets from the manufacturer to verify pinouts and electrical characteristics before finalizing any replacement.

ICGOODFIND Summary: The onsemi FDN304PZ is a highly efficient P-Channel MOSFET prized for its compact SOT-416 package and excellent low on-resistance, making it a cornerstone component for space-constrained, battery-sensitive load switching applications. When seeking a replacement, meticulous attention to electrical specs and package size is paramount for a successful design.

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Keywords: P-Channel MOSFET, Load Switch, Low On-Resistance, SOT-416, Power Management