L293D motor driver: pinout, wiring, the voltage it loses and how hot it gets

The part on Indian and US hobby boards is almost always TI's L293DNE, a 16-pin plastic DIP. The plain L293 (no D) has the same pins and more current, 1 A per channel, but no clamp diodes inside, so a motor on it needs external diodes. Read the full number on the body before you trust a board listing.

The four ground pins in the middle of each row are not spare. TI calls them the heat sink as well as ground and asks for a copper ground plane under them with several vias. On a breadboard they still carry the heat out of the chip, so connect all four.

Each driver copies its input to its output: A high makes Y high (switched to VCC2), A low makes Y low (switched to ground). The pair enable, 1,2EN on pin 1, has to be high for drivers 1 and 2 to drive at all; when it is low both outputs float. Put a motor between 1Y and 2Y and the two inputs choose the direction.

The outputs are bipolar: a Darlington pair pulls low and a similar stage pulls high. That is why each side drops more than a volt even at modest current, unlike a MOSFET bridge. The clamp diodes from each output to VCC2 and to ground catch the motor's kick when a transistor turns off; the flyback diode lesson explains why that kick appears.

The logic side wants 4.5 to 7 V on VCC1. The motor side takes anything from VCC1 up to 36 V on VCC2. Each channel may carry 600 mA continuously and 1.2 A for no more than 100 µs, and the die must stay under 150 °C. TI rates the part for 0 to 70 °C of air around it.

The 1.2 A peak is not a starting-current allowance. 100 µs is far shorter than the time a motor takes to spin up, so a motor whose starting current is above 600 mA overloads the chip on every start.

An input counts as high above 2.3 V and low below 1.5 V, whatever VCC1 is. So a 3.3 V ESP32 or Raspberry Pi Pico can drive the A and EN pins directly. VCC1 still needs 4.5 V or more, so take pin 16 from the board's 5 V pin, not its 3.3 V pin.

At 0.6 A the high side sits 1.4 V below VCC2 (up to 1.8 V) and the low side 1.2 V above ground (up to 1.8 V). The motor loses both: 2.6 V typical, 3.6 V worst case. On a 5 V supply that leaves a 5 V motor with barely half its voltage.

A 5 V microcontroller board drives 1A, 2A and 1,2EN. VCC1 comes from the board's 5 V pin and VCC2 from a 9 V adapter or six AA cells, with the grounds joined. The motor is a small gear motor that draws 0.5 A when loaded and has a 4 Ω winding, the kind sold for two-wheel robot cars.

A robot car puts both motors on one L293D. Each bridge adds its own 1.3 W, so the chip makes 2.8 W typical and the die sits 102 °C above the air: 127 °C (260 °F) in a 25 °C room, 142 °C (287 °F) at 40 °C. With worst-case drops it would need 3.9 W, which puts the die past 150 °C even in a cool room.

The 36.4 °C/W figure comes from a JEDEC test board with copper planes. A chip in a breadboard or on a thin single-sided board runs hotter than these numbers. TI's function table notes a thermal shutdown: past its limit the outputs float and the motors coast, then come back as it cools. A robot that stops and starts by itself on a warm day may be doing exactly that.

A running motor draws less than its winding resistance alone would allow, because it generates a back voltage. Stalled, or in the first moments of a start, only the winding limits the current: 6.4 V / 4 Ω = 1.6 A, well past the 600 mA rating and the 1.2 A peak. The ngspice check in Figure 2 confirms it.

With that motor, a supply of 5 V keeps even a stall inside 600 mA. At 9 V you rely on the motor never jamming and on short starts. Measure your motor's winding resistance with a meter before choosing the supply: VCC2 − 2.6 V divided by that resistance is the stall current.

Hold 1A and 2A for the direction and feed a PWM signal to 1,2EN. TI gives the L293DNE a typical 800 ns delay to switch on and 400 ns to switch off, plus 300 ns edges, so each output pulse comes out about 400 ns shorter than the input pulse. At 20 kHz that is 0.8 % of the period, small enough to ignore. At 20 kHz the motor is also out of the audible range; an Arduino UNO's default analogWrite frequency is lower and you hear it as a whine. The duty cycle and PWM lesson covers the basics.

• Join the motor supply ground and the microcontroller ground. Without it the inputs have no reference and the motor twitches or does nothing.
• Put 100 µF and 100 nF across VCC2 right at the chip; motor current arrives in pulses and a long supply lead cannot deliver them.
• Never take VCC2 from a USB port or an Arduino's 5 V pin for real motors. Motor starts pull the logic supply down and reset the board.
• Tie unused inputs and the unused enable to ground, not open.
• For more than about 0.5 A per motor, or a 3 V to 6 V supply, a MOSFET bridge loses far less voltage; the motor driver ICs lesson compares the types.

The L293 is the only part this datasheet lets us compare like for like. It is the same chip without the diodes, rated 1 A per channel.

1. With no motor, power VCC1 at 5 V and VCC2 at 9 V, enable high, both inputs low. The supply currents should be tens of milliamps at most: TI allows 22 mA on VCC1 and 24 mA on VCC2 with the outputs high.
2. Set 1A high. 1Y (pin 3) should read a little over a volt below VCC2 (TI gives VCC2 − 1.4 V at 0.6 A, and less drop with no load); set 1A low and 1Y reads close to 0 V.
3. Pull the enable low. 1Y and 2Y should float (a meter reads whatever the leads pick up).
4. Fit the motor, run it and measure across 1Y and 2Y. On a 9 V supply at about half an amp expect roughly 6.5 V; much less means the supply sags or the motor draws too much.

Use the L293D for small gear motors up to about 0.5 A, one or two per chip, from a 6 V to 12 V motor supply. Add 2.6 V to the motor's rated voltage when you pick VCC2, take VCC1 from the board's 5 V pin, join the grounds, solder the chip to plenty of copper on all four ground pins and put PWM on the enable pins. Check the motor's stall current before you trust it to a robot. For bigger motors or low supply voltages, move to a MOSFET driver.

Outside India it is stocked by the large distributors as the L293DNE; in India most component shops sell the DIP and ready-made L293D motor shields. Check the marking: some boards sold as L293D carry an L293 or a different driver. Our guide to buying electronic components in India compares ten online sellers and covers how to spot fakes.