Low-side driver for relays and solenoids — what it is and where it fits
The Texas Instruments DRV120PWR is a single-channel low-side N-channel power driver designed to switch relays, solenoids, and other inductive loads. It integrates an internal PWM current-regulation scheme and a status flag output, reducing external components compared to a discrete FET-plus-PWM solution. The load supply range of 6V to 26V covers 12V and 24V industrial rails, and the -40°C to 105°C operating temperature suits factory-floor enclosures, outdoor telecom cabinets, and engine-bay-adjacent equipment.
Load voltage and current — sizing the rail and the load
The load supply (6V to 26V) sets the coil voltage for the relay or solenoid. A 12V nominal coil sees full saturation; a 24V coil runs within the upper half of the range. The driver is a low-side switch, meaning the load connects between the supply rail and the drain of the internal N-channel FET, with the source tied to ground. This topology is standard for grounded-load industrial outputs. The internal PWM limits the average current through the load, which is useful for holding a solenoid engaged at reduced power after the initial pull-in — saves coil heating and supply current.
Fault protection and status reporting
Over-temperature shutdown and undervoltage lockout (UVLO) protect the driver and the load. The status flag output goes active when a fault is detected, which can feed a digital input on a PLC or microcontroller for system-level diagnostics. The On/Off interface (non-inverting input) accepts a simple logic-level signal — no SPI or I²C overhead, which keeps the BOM simple for basic on-off control of a valve or contactor coil.
Package and board integration
The 8-TSSOP package (4.40 mm width) is a surface-mount footprint that fits on compact control PCBs alongside passives and a microcontroller. No external Vcc supply is required — the driver is powered entirely from the load supply, which simplifies the power tree. The Tape & Reel (TR) or Cut Tape (CT) supply format suits both prototyping and production reels.