What this seven-channel Darlington does in a panel
The Texas Instruments ULN2003APWR is a seven-channel NPN Darlington transistor array in the ULx200xA series, built to drive inductive loads like relays, solenoids, and small stepper motors from logic-level signals. Each of the seven outputs sinks up to 500 mA continuously with a maximum load voltage of 50 V, and the inputs are inverting with a 1:1 ratio — a logic high on the input turns the output on, pulling the load to ground. The integrated Darlington pairs give you a current gain of about 1000, so a few milliamps from a microcontroller or PLC output can switch a 500 mA relay coil without an external driver transistor.
Package and board-fit for a field-swap
The 1.0 mm pitch on the TSSOP-16 body means you can route it on a two-layer board without micro-vias; just keep the GND pin (pin 9) trace wide enough for the return current from all seven channels. Operating from -40°C to 70°C, it covers most indoor industrial and commercial environments — fine for a control cabinet or a test fixture, but not rated for under-hood automotive without a temperature-grade check.
Active production and compliance posture
The part is ROHS3 compliant, so it meets the latest EU restriction on hazardous substances — no exemption declarations needed for most commercial builds.