H-Bridge IC (L298N) Symbol
Definition: The H-Bridge IC (L298N) symbol represents the STMicroelectronics L298N dual full-bridge motor driver integrated circuit — a monolithic IC containing two independent H-bridge power stages capable of driving two DC motors or one bipolar stepper motor at up to 2 A per channel and 46 V — depicted in schematics with nine labelled pins: IN1, IN2, ENA (channel A control), OUT A+, OUT A−, OUT B (channel B outputs), VS (motor supply), VSS (logic supply), and GND.
Also known as: L298N, dual H-bridge IC, L298N motor driver, dual full-bridge driver, L298 motor controller, H-bridge motor driver IC.
What the H-Bridge IC (L298N) symbol means
The H-Bridge IC (L298N) symbol denotes a specific dual full-bridge driver IC from STMicroelectronics, widely used in robotics and motor-control projects. The IC contains two complete H-bridges on a single die, each capable of controlling one DC motor bidirectionally or both combined to drive one bipolar stepper motor. The symbol block is labelled 'L298N' and has nine connection points showing the full interface: logic inputs IN1 and IN2 for channel A direction, ENA for channel A PWM enable (speed control), power supply pins VS (motor supply) and VSS (logic supply, 5 V), GND, and three output pins representing channel A (OUT A+ and OUT A−) and channel B output.
In circuit schematics the L298N symbol distinguishes between the logic supply (VSS, 5 V) and the motor supply (VS, up to 46 V), allowing the control logic to operate at a lower voltage while the power stage drives higher-voltage motors. Channel B is controlled by IN3, IN4, and ENB (not all shown in the simplified block symbol but present on the physical IC). The L298N includes internal protection diodes on each output for back-EMF clamping, though external fast-recovery diodes are recommended for inductive loads above 1 A.
How to identify the H-Bridge IC (L298N) symbol
The H-Bridge IC (L298N) symbol is a tall rectangular IC block labelled 'H-BRIDGE IC (L298N)' or simply 'L298N'. On the left side from top to bottom: IN1 (channel A direction input 1), IN2 (channel A direction input 2), ENA (channel A enable/PWM), and the power supply group. On the right side: OUT A+ (channel A motor terminal positive), OUT A− (channel A motor terminal negative), and OUT B (channel B motor output). VS and VSS appear at the top of the block; GND appears at the bottom. The physical L298N IC is a 15-pin Multiwatt or 20-pin PowerSO package.
Function in a circuit
The L298N H-Bridge IC operates two independent full H-bridges from a single chip. Channel A is controlled by IN1 and IN2 (direction) and ENA (enable/speed): with IN1=HIGH and IN2=LOW the motor connected to OUT A+ and OUT A− turns forward; reversed logic reverses the motor. PWM on ENA controls speed by varying average voltage. Channel B operates identically with IN3, IN4, and ENB. The internal transistors are NPN Darlington pairs capable of 2 A continuous and 3 A peak per channel. A 5 V internal regulator supplies logic voltage from the VS supply, eliminating the need for a separate logic supply in some configurations.
Standards: IEC vs ANSI
| IEC 60617 | IEC 60617 does not define a specific symbol for the L298N. In IEC-compliant schematics it is represented as a general rectangular IC block per IEC 60617 conventions, with labelled input, output, supply, and ground pins. The device is specified in STMicroelectronics datasheet L298N DS0043, not an IEC standard. |
|---|---|
| ANSI/IEEE 315 | IEEE 315-1975 (ANSI Y32.2) does not define an L298N-specific symbol. It is drawn as a rectangular IC block with pin labels per general IEEE 315 IC symbol conventions, showing all 15 or 20 pins individually in a chip-level schematic, or as a simplified functional block with the key interface pins in a system-level diagram. |
| Key difference | The IEC and IEEE/ANSI representations of the L298N are functionally identical rectangular block symbols; the only difference is pin-labelling convention. IEC schematics may use European logic-level notation; ANSI schematics use the standard American pin numbering. The physical device is a proprietary IC with no IEC or IEEE symbol standard assigned. |
Terminals / pins
| Pin | Name |
|---|---|
| in1 | IN1 |
| in2 | IN2 |
| ena | ENA |
| outa | OUT A+ |
| outb | OUT A- |
| outc | OUT B |
| vs | VS |
| vss | VSS |
| gnd | GND |
Typical values
VS (motor supply): 4.5 V to 46 V DC. VSS (logic supply): 4.5 V to 7 V (typically 5 V). Output current: 2 A continuous, 3 A peak per channel. Total dissipation: 25 W (Multiwatt package, heatsink required). Logic input voltage: 0–1.5 V = LOW, 2.3–VSS = HIGH. PWM frequency: up to 40 kHz. Quiescent supply current: 36 mA at VS=36 V.
Where the H-Bridge IC (L298N) symbol is used
- Two-wheel and four-wheel drive robots using DC gear motors — each L298N channel independently controls one wheel motor with PWM speed and direction control
- Bipolar stepper motor drivers in 3D printers and CNC machines — both L298N channels together supply the two windings of a bipolar stepper for full-step and half-step operation
- Arduino and Raspberry Pi motor shield circuits — L298N is the most common motor driver IC on beginner-level motor shields and breakout boards
- RC car speed controllers — L298N enables forward/reverse/brake control with PWM speed modulation from a microcontroller
- Automated curtain and blind controllers — bidirectional DC motor control for open/close actuation
- Pump and valve actuator control in irrigation systems — L298N drives small 12 V DC pumps and solenoid valve actuators bidirectionally
- Educational robotics kits — L298N is standard in low-cost motor-driver modules (e.g., L298N red module) widely available from electronics distributors
Example
In an Arduino-based line-following robot schematic, the L298N H-Bridge IC symbol is shown with IN1 and IN2 connected to Arduino digital pins D8 and D9, ENA connected to PWM pin D5, IN3 and IN4 connected to D10 and D11, ENB to PWM pin D6. VS connects to the 12 V battery pack, VSS to the Arduino 5 V rail, and GND to the shared ground. OUT A+ and OUT A− drive the left wheel motor; OUT B+ and OUT B− drive the right wheel motor. The Arduino firmware writes PWM values to ENA and ENB to control speed and sets IN1/IN2 direction bits to steer the robot.
Key facts
- The L298N H-Bridge IC symbol represents the STMicroelectronics L298N dual full-bridge driver, which contains two independent H-bridges capable of 2 A continuous, 3 A peak per channel, at motor supply voltages from 4.5 V to 46 V.
- The L298N symbol has nine key pins: IN1 (channel A input 1), IN2 (channel A input 2), ENA (channel A enable/PWM), OUT A+ (channel A output positive), OUT A− (channel A output negative), OUT B (channel B output), VS (motor supply, up to 46 V), VSS (logic supply, 5 V), and GND.
- Channel A of the L298N is controlled by IN1, IN2, and ENA: IN1 HIGH/IN2 LOW = forward; IN1 LOW/IN2 HIGH = reverse; ENA LOW = coast (outputs disabled); PWM on ENA controls speed.
- The L298N requires external fast-recovery diodes (e.g., 1N4007 or Schottky) across each output transistor for back-EMF clamping when driving inductive loads above 1 A — without these, back-EMF can destroy the output transistors.
- The L298N includes an internal 5 V regulator that can power the logic supply (VSS) from the motor supply (VS) when VS is between 7 V and 46 V, eliminating the need for a separate 5 V supply in many applications.
- The L298N dissipates significant heat in its internal NPN Darlington output transistors (V_CE_sat ≈ 1.8 V at 2 A); a heatsink is mandatory for currents above 1 A to keep junction temperature below 150°C.
- Channel B of the L298N uses IN3, IN4, and ENB pins (not all shown in the simplified block symbol) and is electrically identical to Channel A; both channels share the VS and VSS supplies and GND on the physical IC.
Diagrams that use this symbol
- stepper motor wiring diagram
- stepper motor pinout
- stepper motor circuit diagram
- 4 wire stepper motor wiring diagram
Frequently asked questions
What does the H-bridge IC L298N symbol mean in a circuit diagram?
The H-Bridge IC (L298N) symbol represents a dual full-bridge motor driver IC from STMicroelectronics. It contains two independent H-bridges, each capable of 2 A continuous output, used to control two DC motors or one bipolar stepper motor bidirectionally. The symbol block shows logic control inputs (IN1, IN2, ENA), power supply pins (VS, VSS, GND), and motor output pins (OUT A+, OUT A−, OUT B).
What are the pins on the L298N H-bridge IC symbol?
The key L298N pins in the block symbol are: IN1 and IN2 (channel A direction control), ENA (channel A enable/PWM speed control), OUT A+ and OUT A− (channel A motor terminals), OUT B (channel B motor output), VS (motor supply voltage, 4.5–46 V), VSS (logic supply, 5 V), and GND. The physical 15-pin IC also includes IN3, IN4, ENB, and the second channel's output pins.
How do you control direction with the L298N?
Direction is controlled by the IN1/IN2 logic inputs for channel A: IN1=HIGH and IN2=LOW drives the motor forward (current flows from OUT A+ to OUT A−); IN1=LOW and IN2=HIGH drives it in reverse; IN1=IN2=HIGH or IN1=IN2=LOW applies active braking. ENA must be HIGH for the channel to be active; PWM on ENA controls motor speed.
What supply voltages does the L298N need?
The L298N requires two supply voltages: VS (motor power supply) from 4.5 V to 46 V for the output H-bridge transistors, and VSS (logic supply) from 4.5 V to 7 V (typically 5 V) for the input logic circuitry. When VS is 7 V or higher, the internal 5 V regulator on the L298N can supply VSS directly, so a separate 5 V source is not required.
Why does the L298N get hot?
The L298N uses NPN Darlington pair output transistors with a collector-emitter saturation voltage (V_CE_sat) of approximately 1.8 V at 2 A. At 2 A per channel, each output transistor dissipates about 1.8 V × 2 A = 3.6 W, totalling up to 7.2 W for both channels at full load. A heatsink is mandatory for currents above 1 A to keep the junction temperature below 150°C.
Do I need external diodes with the L298N?
Yes, for inductive loads (DC motors, stepper windings) above about 1 A. When a motor switch turns off, the motor's back-EMF can spike to voltages that exceed the transistor's breakdown voltage. The L298N has internal protection diodes but they are slow (recovery time > 1 µs). External fast-recovery diodes (e.g., 1N5819 Schottky or 1N4007 at lower frequencies) across each output transistor clamp back-EMF spikes and protect the IC.
What is the maximum motor voltage for the L298N?
The L298N motor supply (VS) can be 4.5 V to 46 V. The continuous output current is 2 A per channel (3 A peak). For 12 V DC motors up to 2 A the L298N is a direct fit. For higher-voltage or higher-current applications, alternative ICs such as the VNH5019 (up to 30 V, 12 A) or DRV8701 (up to 45 V, 12 A) should be used.
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