TB6612FNG Motor Driver

What it is

The TB6612FNG is a dual H-bridge motor driver that does the same job as an L298N—standing between a microcontroller’s logic pins and motors that want far more current—but builds its output stage from MOSFETs instead of bipolar transistors. That one change is the whole story: a MOSFET switch drops a few tenths of a volt where the L298N’s stage drops around two.

On a 6 V battery driving 6 V motors, that difference is most of your speed. It is also most of your heat: the L298N wants a heatsink at sustained current, while a TB6612FNG carrier the size of a postage stamp runs merely warm.

How you control it

Each motor takes three signals, plus one shared pin for the chip:

• Two direction pins (AIN1/AIN2 for motor A, BIN1/BIN2 for motor B) select forward, reverse, brake, or coast.
• One PWM pin (PWMA or PWMB) sets speed. Unlike the L298N, where PWM rides on an enable pin, the TB6612FNG has a dedicated PWM input per channel that accepts up to 100 kHz—high enough to switch above the audible range so your robot stops whining.
• One STBY pin, shared. Hold it LOW and both bridges are dead regardless of everything else.

That STBY pin is worth repeating, because it costs beginners an evening: a correctly wired TB6612FNG with STBY left floating or LOW does absolutely nothing, silently, with no error to read.

When to use it

Reach for the TB6612FNG when your motors are small and your battery is precious—which describes nearly every line follower and line maze robot. Small robots run at 6–7.4 V, exactly the range where the L298N’s 2 V tax hurts most, and they run on a battery you would rather not waste as heat.

Stay with the L298N when your motor supply exceeds 13.5 V, which the TB6612FNG cannot accept, or when you need more than about 1.2 A continuous per channel.

Wiring and gotchas

• Drive STBY HIGH. The first thing your setup() should do after pinMode.
• Two supplies, one ground. Motor battery to VM, Arduino 5 V to VCC, and all grounds tied together—Arduino, driver, sensor array, and battery negative. A missing common ground gives control signals no reference, and the failure is silent.
• Respect 13.5 V. There is no on-board regulator and no headroom above the maximum motor supply. A 3S lithium pack at 12.6 V nominal will exceed it when freshly charged.
• A motor spinning the wrong way is a two-second fix. Swap that motor’s two output wires, or invert its direction logic in firmware. Do this before you tune anything else, or you will chase a control bug that is really a wiring one.