The L298N Motor Driver: Quick Verdict and Sizing Rule of Thumb

The L298N is a classic, bipolar junction transistor (BJT) based dual H-bridge integrated circuit. It can independently drive two brushed DC motors (up to 2A continuous per channel) or one 2-phase bipolar stepper motor. While it remains a staple in educational kits and high-voltage hobby projects due to its low upfront cost (typically $2 to $4 per module), its BJT architecture introduces significant voltage drops and thermal inefficiencies that modern MOSFET drivers have largely solved.

The Golden Sizing Rule: Never size an L298N channel for a motor's stall current if that stall current exceeds 2A. Furthermore, derate the continuous current limit by 20% (to 1.6A) if you are running the module without active cooling or a massive heatsink.

Worked Load Example: Sizing for a 12V Gearmotor

Suppose you are building a small rover using 12V DC planetary gearmotors. The datasheet specifies a no-load current of 0.25A and a stall current of 1.8A.

  • Can the L298N handle it? Yes. The 1.8A stall current is under the 2A absolute maximum, and your normal operating current under load will likely hover around 0.8A to 1.2A.
  • The Voltage Drop Catch: Because the L298N uses BJTs, it suffers from a saturation voltage drop ($V_{CE(sat)}$) of roughly 2.0V to 2.5V at 1A. If you feed the module 12V, your motor will only see about 9.5V to 10V at the terminals. If your application requires the full 12V torque curve, you must supply the L298N with 14V to compensate for the internal losses.

For a deeper look at the internal BJT switching mechanics and thermal shutdown thresholds, refer to the STMicroelectronics L298 Datasheet, which details the Multiwatt15 package thermal resistance.

Motor Type Compatibility: DC, Stepper, and Servo Profiles

A common mistake on the bench is treating all motors as interchangeable loads. The L298N is strictly an H-bridge; it reverses polarity and modulates voltage. It does not generate step pulses or read position feedback. Below is a breakdown of which motor types fit this load profile and what the L298N can actually drive.

Motor Type Torque Curve Profile Control Needs Typical Cost L298N Compatibility
Brushed DC Max torque at stall, drops linearly as RPM increases. PWM for speed, H-bridge for direction. $2 - $15 Native. Ideal for channels A and B.
Bipolar Stepper High holding torque at zero RPM, drops sharply at high speeds. Sequential coil energizing (step/direction pulses). $10 - $30 Native. Use both channels for one 4-wire stepper.
RC Hobby Servo High torque across a limited angular range (usually 180°). 50Hz PWM signal wire, separate VCC/GND power. $5 - $25 Incompatible. Do not wire servos to the H-bridge outputs.

Why Servos Fail on the L298N: Standard 3-wire RC servos contain their own internal H-bridge and potentiometer feedback loop. They require a clean 5V/6V DC power supply and a low-current 50Hz PWM signal on the data pin. Routing servo power through the L298N's motor terminals will destroy the servo's internal control board. Drive servos directly from your microcontroller's GPIO (for signal) and a dedicated BEC or buck converter (for power).

Wiring and Terminal Identification for the L298N Module

The standard red L298N module breaks out the IC's pins into screw terminals and male headers. Miswiring the logic supply versus the motor supply is the fastest way to brick the onboard 5V regulator.

Terminal / Pin Function Connection Target Critical Notes
12V / VCC Motor Power Supply (VS) Battery pack or bench supply (7V to 35V max). Keep under 12V if using the onboard 5V regulator jumper.
GND Common Ground Battery GND and Microcontroller GND. Must be shared with the MCU for logic reference.
5V Logic Supply / Output MCU 5V pin (or powered via jumper). If VS > 12V, remove the jumper and feed 5V INTO this pin.
ENA / ENB Enable / PWM Speed MCU PWM-capable GPIO pins. Remove factory jumper caps to control speed via code.
IN1, IN2, IN3, IN4 Direction Logic MCU Digital GPIO pins. Requires minimum 2.3V for a logic HIGH (3.3V logic safe).
OUT1-OUT4 Motor Outputs Motor terminals. OUT1/2 for Motor A; OUT3/4 for Motor B.
The 5V Regulator Trap: Most modules include an LM7805 linear regulator with a jumper cap near the 12V terminal. This steps down the motor supply to power the L298N logic and provide 5V to your Arduino. However, if your motor supply exceeds 12V, the LM7805 will overheat and fail, taking the logic circuit with it. If running 24V motors, remove the jumper and power the logic side independently.

Failure Signatures: Diagnosing Hum, Overheat, and Stall

When a motor drive circuit fails, the symptoms usually manifest acoustically or thermally before the silicon actually melts. Here is how to read the failure signatures of an L298N-driven system.

1. The Audible Whine or 'Hum'

Symptom: The motor emits a high-pitched whine or low hum without rotating, or the whine is present during normal operation.
Cause: If the motor isn't moving, the PWM frequency from your microcontroller is likely too low (under 1kHz), causing the motor coils to act as speakers. If the motor is moving but whining, you are experiencing 'stall-adjacent' operation where the mechanical load exceeds the available torque at the reduced voltage.
Fix: Increase the PWM frequency in your code to at least 2kHz (above human hearing range). For Arduino, use the setPwmFrequency() timer manipulation; for ESP32, configure the LEDC peripheral to 5000Hz.

2. Thermal Overload (The 'Hot Finger' Test)

Symptom: The L298N heatsink is too hot to touch (>80°C) within two minutes of operation, and the motor randomly cuts out, then restarts.
Cause: You have triggered the internal thermal shutdown circuit (typically activates at 150°C junction temperature). The Multiwatt15 package has a junction-to-ambient thermal resistance of roughly 35°C/W. At 2A continuous with a 2V drop, the IC dissipates 4W. That yields a 140°C temperature rise above ambient.
Fix: Add forced air cooling (a 5V fan), reduce the continuous load, or switch to a MOSFET-based driver. Never bypass thermal shutdown by submerging the IC or applying liquid coolants.

3. The Dead Stall (Brownout Reset)

Symptom: The motor stops abruptly, the microcontroller restarts (you see the onboard LED blink), and the system hangs.
Cause: Inductive kickback or voltage sag. When a DC motor starts or reverses, it draws stall current. This massive current spike sags the battery voltage. If the logic supply dips below the microcontroller's brownout detection threshold (e.g., 2.7V for an ATmega328P), the MCU resets.
Fix: Separate the high-current motor power wiring from the low-current logic wiring. Add a large electrolytic capacitor (e.g., 1000µF, 25V) directly across the L298N's 12V and GND screw terminals to buffer transient current demands.

The Decision Path: L298N vs. Modern MOSFET Drivers

The L298N was designed in the 1990s. In 2026, MOSFET-based H-bridges offer vastly superior efficiency, dropping only 0.2V to 0.5V instead of 2.5V. Use the decision matrix below to select the correct driver for your specific load profile.

If Your Project Requires... Then Choose This Driver Why It Wins
Battery power (6V - 12V), maximum efficiency, and compact size. TB6612FNG (e.g., Pololu or SparkFun breakout) MOSFET architecture yields <0.5V drop. Handles 1.2A continuous (3.2A peak). No massive heatsink required.
High voltage (15V to 35V) solenoids, large DC actuators, or cheap educational kits. L298N Module Unbeatable for high-voltage tolerance up to 35V. Screw terminals handle thick 14 AWG wires easily.
Stepper motors requiring microstepping and silent operation. TMC2209 or DRV8825 The L298N cannot microstep. Dedicated chopper drivers handle coil current regulation and stealth-chop silence.
Low-voltage (3V - 6V) micro-motors where every volt counts. DRV8833 or DRV8871 The L298N's 2V drop will starve a 3V motor. The DRV8833 operates down to 2.7V with minimal loss.

The Final Recommendation

Do not default to the L298N simply because it is the first result in a search engine. If you are building a battery-powered mobile robot operating between 6V and 12V, buy the TB6612FNG. The extra hour spent learning its smaller pinout will reward you with 30% longer battery life and a driver that doesn't require a cooling fan.

However, if you are switching 24V industrial actuators, driving heavy 12V linear actuators where efficiency is secondary to raw voltage tolerance, or building a ruggedized classroom kit where students will inevitably short the outputs, the L298N remains a robust, forgiving, and highly capable workhorse. Just respect the 2A continuous limit, share your grounds, and buffer your power rails.

For further reading on H-bridge topologies and the physics of inductive flyback, the All About Circuits H-Bridge Tutorial provides an excellent schematic-level breakdown of why flyback diodes (included on the L298N module) are non-negotiable.