TI / ST / Toshiba · Integrated circuit

ULN2003 Darlington Array

Seven open-collector Darlington sinks with built-in clamp diodes, for relays, solenoids and 28BYJ-48 steppers.

1.Pinout diagram

Pins 1-8

ULN2003

Pins 9-16

Pin detail

Hover a pin for its mappings and gotchas. Click to keep it here.

Fig. 1. ULN2003 Darlington Array, PDIP-16. Hover or tap a signal to light up every pin that carries it.

Outputs sink only. The load goes between your positive rail and the output pin, never between the output and ground. Getting this backwards is why nothing switches on.
Pin 9 is COM, the common cathode of the flyback diodes. Tie it to the load's positive rail or the diodes do nothing and inductive kick goes through the chip instead.
The output order is reversed against the inputs: IN1 on pin 1 drives OUT1 on pin 16, IN2 on pin 2 drives OUT2 on pin 15, and so on down to IN7 and OUT7 on pins 7 and 10.
500 mA per channel, but not on all seven at once. The package dissipation limit lands around 1.5 W total, so a full load of seven relays will overheat it.
Darlington saturation drop is about 1 V at 350 mA, wasted as heat. The TBD62083A is pin compatible, DMOS, and drops a third of a volt.
ULN2003 inputs are sized for 5 V logic. ULN2004 is the same part with input resistors for 6 to 15 V CMOS.
For eight channels use the ULN2803, which is DIP-18 with a different pinout rather than a wider version of this one.

What has to go around the chip before it will run.

Fig. 2. Driving an inductive load, drawn from Table 1. Crossing wires are not connected.

Table 1. External parts, and why each one is there.
Part	Between	Why
Wire link	COM (9) to VCC	Connects the internal clamp diodes to the load's rail. Without it the flyback goes through the chip.
Load	COM (9) to OUT1 (16)	Coil or solenoid from the positive rail to an output. The outputs sink only.

500 mA per channel, but not on all seven at once. Package dissipation caps the total around 1.5 W.

Every pin, alias and mapping. This is the table that prints.

Table 2. Pin assignments.

Complete pin reference for ULN2003 Darlington Array
Pin	Name	Also called	Functions	Notes
1	IN1	1B	Channel 1 input	Drives OUT1 on pin 16.
2	IN2	2B	Channel 2 input
3	IN3	3B	Channel 3 input
4	IN4	4B	Channel 4 input
5	IN5	5B	Channel 5 input
6	IN6	6B	Channel 6 input
7	IN7	7B	Channel 7 input
8	GND	E	Ground, common emitter
9	COMto 50 V	-	Flyback diode common	Connect to the load's supply rail. Without it the clamp diodes are not in circuit.
10	OUT7	7C	Channel 7 output	Open collector sink, 500 mA.
11	OUT6	6C	Channel 6 output
12	OUT5	5C	Channel 5 output
13	OUT4	4C	Channel 4 output
14	OUT3	3C	Channel 3 output
15	OUT2	2C	Channel 2 output
16	OUT1	1C	Channel 1 output	Driven by IN1 on pin 1, at the opposite corner.

Found a wrong pin? The whole board is one file, data/boards/uln2003.json.