The BSS84LT1G is a P-channel enhancement-mode MOSFET featuring a -50 V drain-to-source voltage, low on-resistance, and low power consumption. It is widely used in load switching, power management, battery protection, and portable electronic devices.
This article provides an overview of the BSS84LT1G, covering its key specifications, pin configuration, operating principle, typical applications, and more to help engineers better understand its characteristics and select the right device for their designs.
What Is BSS84LT1G?
The BSS84LT1G P-channel MOSFET comes in a compact SOT-23 surface-mount package and is primarily designed for low-voltage, low-current switching, logic-level translation, and high-side load control. With a maximum drain-to-source voltage (VDS) of -50 V and a continuous drain current (ID) of up to -130 mA, it is well suited for handling low-power control signals.
In addition, the device can be fully turned on with a relatively low gate drive voltage, and some versions feature integrated ESD protection. The BSS84LT1G is widely used for logic-level shifting between different voltage domains, such as 3.3 V and 5 V systems, as well as for power switching of low-power loads controlled by microcontrollers (MCUs).
BSS84LT1G Operating Principle
The BSS84LT1G is controlled by the voltage between its gate (G) and source (S) terminals (VGS). When the gate voltage is lower than the source voltage, making VGS negative and below the gate-to-source threshold voltage (VGS(th)), the MOSFET turns on, allowing current to flow from the source to the drain. When the gate voltage approaches or equals the source voltage, the MOSFET turns off, cutting off the current to the load.
Since P-channel MOSFETs are typically placed on the positive power rail, the BSS84LT1G is widely used in high-side switching applications. By simply changing the gate voltage, a microcontroller (MCU) or control circuit can switch power to the downstream load on or off without requiring a complex gate driver.
BSS84LT1G Specifications
Parameter | Value |
Part Number | BSS84LT1G |
Description | MOSFET P-CH 50V 130MA SOT-23 |
Lead Free Status / RoHS Status | Lead free / RoHS Compliant |
Vgs (Max) | ±20V |
Current - Continuous Drain (Id) @ 25°C | 130mA (Ta) |
Operating Temperature | -55°C ~ 150°C (TJ) |
Rds On (Max) @ Id, Vgs | 10 Ohm @ 100mA, 5V |
FET Type | P-Channel |
Drain to Source Voltage (Vdss) | 50V |
Mounting Type | Surface Mount |
Vgs(th) (Max) @ Id | 2V @ 250µA |
Power Dissipation (Max) | 225mW (Ta) |
Moisture Sensitivity Level (MSL) | 1 (Unlimited) |
Drive Voltage (Max Rds On, Min Rds On) | 5V |
Input Capacitance (Ciss) (Max) @ Vds | 30pF @ 5V |
Package | SOT-23-3 (TO-236) |
Base Part Number | BSS84 |
BSS84LT1G Pin Configuration
Pin 1 – Gate (G)
The Gate is the control terminal of the MOSFET and has a very high input impedance, requiring almost no input current. The BSS84LT1G turns on when the gate voltage is pulled below the source voltage, making VGS sufficiently negative. When the gate voltage approaches the source voltage, the MOSFET turns off.
Pin 2 – Source (S)
The Source is the current input terminal and is typically connected to the positive power supply (VCC) in P-channel MOSFET applications. Because of this configuration, the BSS84LT1G is widely used for high-side load switching.
Pin 3 – Drain (D)
The Drain is connected to the load. When the MOSFET is turned on, current flows from the Source to the Drain, supplying power to the load. When the device is off, the current path is interrupted, disconnecting the load from the power source.
BSS84LT1G Design Considerations
In practical circuit design, understanding and optimizing the following six factors can help ensure the long-term reliability of the BSS84LT1G.
l Gate Drive Voltage: The threshold voltage (VGS(th)) is -1 V to -2 V. For full turn-on, ensure the gate voltage reaches -4.5 V or -10 V relative to the source. In low-voltage systems (e.g., 1.8 V), incomplete turn-on may increase power dissipation.
l PCB Thermal Layout: The SOT-23 package has limited heat dissipation (up to 225 mW). Use larger copper areas connected to the Drain pin and avoid placing heat-generating components too close together.
l RDS(on) Selection: With an RDS(on) of approximately 3.5–5 Ω, calculate conduction loss (P = I² × RDS(on)) and verify that the resulting voltage drop does not affect the load.
l Switching Frequency: The low input capacitance (Ciss ≈ 45 pF) enables fast switching. At high PWM frequencies, switching losses increase, so a small gate resistor can help reduce ringing.
l Current Limitation: The maximum continuous drain current is approximately -130 mA. It is intended for low-power loads such as signal switching, LEDs, or relays, not motors or other high-current devices.
l Reverse Polarity Considerations: The device includes an intrinsic body diode. In reverse-polarity or power-switching circuits, correct Source and Drain orientation is essential, as the body diode can conduct even when the MOSFET is turned off.
BSS84LT1G Features
l SOT−23 Surface Mount Package Saves Board Space
l BV Prefix for Automotive and Other Applications Requiring Unique Site and Control Change Requirements; AEC−Q101 Qualified and PPAP Capable
l These Devices are Pb−Free and are RoHS Compliant
l P-Channel Enhancement-Mode MOSFET for High-Side Switching Applications
l Low On-State Resistance Reduces Conduction Losses
l Low Gate Threshold Voltage for Easy Logic-Level Drive
l Fast Switching Performance with Low Input Capacitance
l Low Leakage Current Improves Power Efficiency in Standby Mode
l Suitable for Load Switching, Power Management, and Voltage Level Translation Applications
l Available in Tape and Reel Packaging for Automated Assembly
BSS84LT1G Applications
1. Load Switching
BSS84LT1G is commonly used as a high-side load switch in low-power electronic systems. Its P-channel MOSFET structure allows the device to control power delivery to downstream components with simple gate drive circuits. It is suitable for switching small loads such as LEDs, sensors, relays, and other peripheral devices.
2. Power Management Circuits
With low power consumption and compact SOT-23 packaging, BSS84LT1G is widely applied in power management designs. It can be used for power distribution, power gating, and standby power control in battery-powered and embedded systems to improve energy efficiency.
3. Battery-Powered Devices
BSS84LT1G is suitable for portable devices that require efficient power control. It can be integrated into battery management circuits to disconnect or reconnect power paths, helping reduce standby current and extend battery life in devices such as handheld electronics and wearable products.
4. Logic Level Translation
The device can be used for voltage level shifting between different logic systems, such as 3.3 V and 5 V interfaces. By controlling the MOSFET switching state, BSS84LT1G helps achieve reliable signal conversion in microcontroller-based systems and communication circuits.
5. Embedded Systems and Consumer Electronics
Due to its small size and easy integration, BSS84LT1G is commonly used in compact electronic devices. Typical applications include MCU-controlled power switches, smart home devices, portable instruments, and other low-power consumer electronics.
6. Industrial Control and Interface Circuits
BSS84LT1G can also be applied in industrial control systems for low-current switching tasks. It is suitable for controlling indicator circuits, interface modules, and auxiliary power supplies where compact size and reliable switching performance are required.
BSS84LT1G Package
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