L293D PCB Design Guide: Footprint, Pinout, and Alternatives
Quad half-H motor driver with built-in flyback diodes, 600 mA per channel.
The L293D is the classic quadruple half-H driver: four Darlington-output half bridges that pair up into two full H-bridges for two brushed DC motors, one bipolar stepper, or four independent solenoid and relay loads. The motor supply spans 4.5 V to 36 V, each channel is rated 600 mA continuous with 1.2 A nonrepetitive peaks, and — this is what the D suffix means — the flyback clamp diodes are on the chip. TI still ships it as an active part in exactly one package, the PDIP-16 it has worn since 1986.
Pick it with open eyes, because this is a bipolar design and the output stage eats roughly 2.6 V typical across a full bridge at 600 mA. On a high motor rail that is a rounding error; on a low-voltage pack it is a large slice of the supply, delivered to the motor as lost speed and to the PDIP as heat. The L293D earns its keep where the 36 V ceiling, the breadboard-friendly through-hole package, the built-in diodes, or an existing footprint matter. For anything battery-powered, a modern MOSFET bridge like the DRV8833 drops far less; see the alternatives below.
The recurring board-level mistakes are consistent: forgetting the bridge drop and wondering why motors crawl, sizing for running current when stall current is what the driver actually sees, leaving the ground pins without the copper that is the package's only heat-sink path, strapping the logic supply to a high motor rail, and assuming the internal diodes make bypassing and layout optional. Each is covered below.
What breaks boards
Budget ~2.6 V of bridge drop — this is not a MOSFET driver
The Darlington output stage drops serious voltage: VOH sits at VCC2 − 1.4 V typical (VCC2 − 1.8 V min) and VOL at 1.2 V typical (1.8 V max), both specified at 600 mA. Push a motor through a full bridge and roughly 2.6 V typical vanishes before the load ever sees it. That is the answer to the perennial "my motors run slow off the L293D" thread, and it is why battery designs are wrong for this part: the drop is roughly fixed, so the lower VCC2 is, the bigger the fraction of the supply the driver eats.
The drop becomes heat, and the GROUND pins are the only heat sink
Whatever the bridge drops at 600 mA is dissipated in the PDIP, and RθJA is 36.4 °C/W against a 150 °C junction maximum. TI is explicit that heatsinking is critical for high-current drive: the four GROUND pins (4, 5, 12, 13) are the heat-sink path and belong on a ground plane or copper pour through multiple solid vias. Socketed builds and thin single traces push the die into thermal shutdown, which drops the outputs to high impedance with no fault flag — the motor just stops. Note the 0 °C to 70 °C rating: commercial temp only.
600 mA is an absolute maximum — size for stall current, not running current
The 600 mA per-channel figure lives in the Absolute Maximum Ratings table; it is a ceiling, not an operating point. The 1.2 A peak rating is nonrepetitive with t ≤ 100 µs, so it does not cover the inrush of every PWM cycle or a slow start-up ramp. DC motors pull stall current at power-up and on reversal, and a gearmotor that cruises comfortably below 600 mA can blow through the limit when jammed. There is no current limiting on this part — thermal shutdown is the only protection — so a stalled mechanism cooks the driver until the die overheats.
VCC1 is a 4.5–7 V logic rail — never strap it to a high motor supply
The two supplies are not interchangeable. VCC2 runs to 36 V, but VCC1 is specified at 4.5 V to 7 V — nominally 5 V ± 0.5 V — and feeds the input logic. Tying VCC1 to VCC2, the tempting single-supply hookup, is only in spec when the motor rail itself sits inside that window; anything higher needs a separate logic rail. Budget the current too: ICC1 is 35 mA typical and 60 mA max with the outputs low, a real load for a small regulator. On the plus side, VIH is 2.3 V minimum, so a 3.3 V GPIO drives the inputs directly.
The internal diodes are the D's whole point — bypassing and layout still matter
The L293D clamps inductive kicks on-chip: VOKH is VCC2 + 1.3 V typical and VOKL 1.3 V typical at 600 mA, so motor windings, solenoids, and relays need no external diodes. The clamp current still returns through your supply and ground, so follow TI's requirements: bypass capacitors of 0.1 µF or greater at both the VCC1 and VCC2 pins, and place the device near the load with short output traces to reduce EMI. One trap: the plain L293 has no internal diodes, so dropping one into an L293D footprint without adding external clamps leaves the first inductive transient unclamped.
Key specifications
| Parameter | Value | Source |
|---|---|---|
| Supply range | VCC1: 4.5 V min / 7 V max; VCC2: VCC1 min / 36 V max | SLRS008D Rev D, Section 6.3 Recommended Operating Conditions |
| Continuous output current | -600 to 600 mA abs max per channel (feature bullet: 'Output Current 1 A Per Channel (600 mA for L293D)') | SLRS008D Rev D, Section 6.1 Absolute Maximum Ratings, 'Continuous output current, IO: L293D' row + Section 1 Features |
| Peak output current | -1.2 to 1.2 A (nonrepetitive, t <= 100 us) | SLRS008D Rev D, Section 6.1 Absolute Maximum Ratings, 'Peak output current, IO (nonrepetitive, t <= 100 us): L293D' row |
| Output voltage drop | VOH = VCC2 - 1.8 V min / VCC2 - 1.4 V typ (L293D: IOH = -0.6 A); VOL = 1.2 V typ / 1.8 V max (L293D: IOL = 0.6 A) - roughly 2.6 V typ total drop across a full bridge | SLRS008D Rev D, Section 6.5 Electrical Characteristics, VOH and VOL rows |
| Output clamp voltage (internal diodes) | VOKH = VCC2 + 1.3 V typ (L293D: IOK = -0.6 A); VOKL = 1.3 V typ (L293D: IOK = 0.6 A) | SLRS008D Rev D, Section 6.5 Electrical Characteristics, VOKH and VOKL rows |
| Logic supply current (ICC1) | 35 mA typ / 60 mA max (IO = 0, all outputs at low level); 13 mA typ / 22 mA max (all outputs at high level); 8 mA typ / 24 mA max (all outputs at high impedance) | SLRS008D Rev D, Section 6.5 Electrical Characteristics, ICC1 rows |
| Thermal / operating temperature | RthetaJA = 36.4 C/W (NE PDIP, 16 pins); TJ max = 150 C; TA operating 0 to 70 C | SLRS008D Rev D, Section 6.4 Thermal Information + Section 6.1 Absolute Maximum Ratings + Section 6.3 Recommended Operating Conditions |
| Logic inputs | VIH = 2.3 V min; input voltage abs max 7 V; all inputs are TTL compatible and tolerant up to 7 V | SLRS008D Rev D, Section 6.3 Recommended Operating Conditions (VIH row) + Section 6.1 Absolute Maximum Ratings (input voltage VI row) + Section 8.1 Overview |
| Ground / heat-sink pins | Pins 4, 5, 12, 13 (GROUND): device ground and heat sink pin; connect to printed-circuit-board ground plane with multiple solid vias | SLRS008D Rev D, Section 5 Pin Configuration and Functions, GROUND row |
| Supply bypassing | VCC1 is 5 V +/- 0.5 V; VCC2 can be same supply as VCC1 or a higher voltage supply with peak voltage up to 36 V; bypass capacitors of 0.1 uF or greater should be used at VCC1 and VCC2 pins; no power-up or power-down supply sequence order requirements | SLRS008D Rev D, Section 10 Power Supply Recommendations |
Verified against the manufacturer datasheet on 2026-07-10. Confirm the current revision before production use.
Alternatives
- SN754410: TI's pin-compatible quad half-H driver rated 1 A per channel; the common drop-in upgrade for an existing L293D footprint.
- DRV8833: TI's modern dual H-bridge (2.7–10.8 V) with MOSFET outputs; far lower voltage drop, the right call for low-voltage battery designs.
- DRV8871: TI single H-bridge, 6.5–45 V, 3.6-A peak, MOSFET outputs with integrated current regulation — one bigger motor instead of two small ones.
- L298N: STMicroelectronics dual full-bridge from the same Darlington era, 2 A per bridge; requires external clamp diodes.
Common questions
- What is the difference between the L293 and the L293D?
- They share the same datasheet and pinout. The L293 is rated 1 A per channel but has no internal clamp diodes; TI requires external high-speed diodes for inductive loads. The L293D trades down to 600 mA per channel and integrates the diodes (VOKH = VCC2 + 1.3 V typical). The substitution is only safe in one direction: an L293 dropped into an L293D design has no flyback protection.
- Why do my motors run slowly on an L293D?
- Because the Darlington bridge drop comes out of the motor's voltage: VOH is VCC2 − 1.4 V typical and VOL 1.2 V typical at 600 mA, roughly 2.6 V typical across a full bridge, and each side can drop up to 1.8 V worst case. Either raise VCC2 to compensate — the ceiling is 36 V — or move to a MOSFET driver like the DRV8833.
- Can a 3.3 V microcontroller drive the L293D directly?
- The inputs, yes: VIH is 2.3 V minimum and all inputs are TTL compatible and tolerant up to 7 V, so 3.3 V GPIOs work without level shifting. VCC1 cannot run from 3.3 V, though — it is specified at 4.5 to 7 V, nominally 5 V ± 0.5 V — so the board still needs a 5 V rail for the logic supply.
- Do I need external flyback diodes with an L293D?
- For ordinary inductive loads, no. The D suffix means the clamp diodes are on-chip, clipping transients about 1.3 V beyond the rails (VOKH = VCC2 + 1.3 V typical, VOKL 1.3 V typical). You still need 0.1 µF or greater bypass capacitors at both supply pins. Do not carry the assumption over to the plain L293, which requires external high-speed clamp diodes.