Boost regulator for single-LED-string backlights
The LM3519MK-20/NOPB is a fixed-frequency, step-up (boost) DC-DC regulator from Texas Instruments, designed specifically to drive a single series string of white LEDs for backlight applications. It integrates the switching MOSFET internally and delivers a regulated 20 V output at up to 20 mA per channel from a 2.7 V to 5.5 V input supply. The 5.4 MHz switching frequency lets you use a small inductor and ceramic capacitors, shrinking the total solution footprint into a TSOT-23-6 package.
PWM dimming and the 20 V output ceiling
Brightness control is handled through a PWM dimming input, which lets you modulate the LED current without affecting colour temperature — standard practice for display backlights. The 20 V output rail is the maximum compliance voltage for the LED string; if your backlight needs more than that (e.g. six or more white LEDs in series), this part won't support it. For a typical three- or four-LED string at 20 mA, the 20 V ceiling gives about 5 V headroom per LED, which is comfortable for most white LEDs at full brightness.
Temperature grade and where it fits
Rated for -40°C to 85°C ambient, this is an industrial-temperature part. It will handle outdoor telecom panels, automotive cabin displays, and factory HMI backlights without issue. Not rated for under-hood or engine-bay environments — those would need the 125°C rated LM2703 variant if you need higher temperature tolerance.
Lifecycle and sourcing reality
The LM3519MK-20/NOPB carries an Active lifecycle status and is ROHS3 compliant.