BASH21LT1G

The onsemi BASH21LT1G is an N-channel logic-level MOSFET designed for low-voltage switching and load-driving applications. It is constructed using advanced planar MOSFET technology optimized for low on-resistance and fast switching performance. The device is packaged in a compact SOT-23 surface-mount configuration, enabling high-density PCB integration and minimal board footprint. Its design emphasizes low gate-threshold voltage, low conduction losses, and robust thermal characteristics, making it suitable for battery-powered and portable systems where efficiency and space are critical.

## Device Function and Positioning

The BASH21LT1G functions as a single N-channel MOSFET capable of switching and controlling DC loads in low-voltage circuits. As a logic-level device, it is compatible with gate drive voltages as low as 2.5 V, allowing direct interfacing with standard microcontroller and logic-level control circuits. The device is primarily positioned for low-voltage power management, load switching, and signal-level switching where minimal conduction loss and fast response are required. Its SOT-23 package facilitates compact design in consumer electronics, communication modules, and industrial low-power applications.

## Semiconductor Structure and Technology

The BASH21LT1G utilizes a planar N-channel MOSFET structure optimized for low on-resistance and fast gate response. The device operates in enhancement mode, requiring a positive gate-source voltage to conduct. The planar construction ensures stable performance across temperature and voltage variations while providing low leakage current. The logic-level gate enables operation with standard microcontroller I/O voltages, reducing the need for additional driver circuitry.

The SOT-23 package offers efficient thermal conduction to the PCB, supporting moderate current handling while maintaining compact assembly dimensions. The combination of planar MOSFET architecture and optimized packaging supports reliable switching in both DC-DC conversion and general-purpose load-driving circuits.

## Absolute Maximum Ratings

The confirmed maximum ratings for the BASH21LT1G are:

Drain-to-source voltage (VDS): 30 V

Gate-to-source voltage (VGS): ±12 V

Continuous drain current (ID) at 25°C: 2.2 A

Pulsed drain current (ID,pulse): 8.8 A

Power dissipation (PD) at 25°C: 0.5 W

Operating junction temperature range: -55°C to +150°C

Storage temperature range: -55°C to +150°C

The device exhibits a low thermal resistance from junction to ambient in SOT-23 layout conditions, emphasizing the importance of adequate PCB copper area for heat dissipation.

## Static Electrical Characteristics

Key static parameters include:

Threshold voltage (VGS(th)): 0.8 V to 1.8 V

Maximum on-resistance (RDS(on)):

70 mΩ at VGS = 4.5 V

110 mΩ at VGS = 2.5 V

These characteristics indicate low conduction loss under typical logic-level gate drive conditions. Gate leakage current is negligible, supporting low standby power consumption in battery-powered applications. Drain-source leakage is minimal under rated voltage conditions, ensuring minimal parasitic loss.

## Switching Characteristics

The BASH21LT1G demonstrates fast switching suitable for low-voltage DC applications. Typical dynamic parameters include:

Total gate charge (Qg): 3.5 nC at VDS = 25 V

Gate-source charge (Qgs): 1.0 nC

Gate-drain charge (Qgd): 1.2 nC

Turn-on delay time: 10 ns

Rise time: 15 ns

Turn-off delay time: 35 ns

Fall time: 20 ns

These parameters support rapid switching with minimal energy loss, making the device effective in PWM-controlled power paths, microcontroller-driven load switching, and low-power DC-DC circuits.

## Thermal and Package Considerations

The SOT-23 package provides a small footprint with adequate thermal conduction for the device’s current rating. PCB layout significantly affects thermal performance; sufficient copper area on the drain pad improves heat dissipation, especially during continuous high-current operation. Designers should ensure that power dissipation remains within limits to prevent exceeding the junction temperature maximum of 150°C.

## Typical Applications

The BASH21LT1G is suitable for low-voltage, moderate-current switching applications, including:

* Microcontroller-controlled load switches

* Battery-powered devices requiring low-voltage load management

* Signal switching and level shifting in communication interfaces

* DC-DC converter low-side switching

* Power-path selection and distribution in portable electronics

* Consumer electronics and embedded systems with compact PCB requirements

Its logic-level gate and fast switching capabilities make it highly suitable for systems where microcontrollers provide direct switching control without additional gate driver circuitry.

## Design Considerations

Designers using the BASH21LT1G should ensure gate drive voltage exceeds the threshold sufficiently to minimize RDS(on) and reduce conduction losses. The absolute maximum VGS of ±12 V must not be exceeded to avoid gate oxide stress. For applications with high switching frequency, gate drive impedance and layout parasitic inductance should be minimized to maintain fast transitions and reduce overshoot. Adequate PCB thermal design is required to maintain junction temperatures within safe operating limits.

## Conclusion

The onsemi BASH21LT1G is a logic-level N-channel MOSFET optimized for low-voltage, moderate-current switching applications. With a 30 V drain-source rating, 2.2 A continuous current capability, low RDS(on) of 70 mΩ at 4.5 V gate drive, and fast switching performance, it provides an efficient solution for microcontroller-driven load control, power-path selection, and battery-powered devices. Its compact SOT-23 package, combined with low gate drive requirements and robust thermal characteristics, makes it ideal for portable electronics, embedded systems, and other applications where space efficiency and low power loss are critical.