LTR390 UV Sensor Module – UVA and Ambient Light, I2C, 3–5V with Onboard Regulator

The LTR390 UV Sensor module is a compact breakout module built around the Lite-On LTR-390UV-01, a digital ambient light sensor (ALS) and ultraviolet (UV) sensor in a single 2mm × 2mm surface-mount package. The sensor provides true UV-spectrum measurement with a peak spectral response in the 300–350nm UVA band, alongside a separate ambient light channel covering 500–600nm. This dual-channel capability allows the module to report both visible-light intensity (in lux) and UV intensity from a single I²C device, making it suitable for sun-exposure monitoring, UV index estimation, and ambient-light-adaptive systems.

The module operates from a 3V to 5V DC supply and includes an onboard low-dropout regulator that converts the input down to the 3.3V required by the sensor core. I²C logic pins are level-shifted, so the module can interface directly with both 3.3V and 5V microcontrollers without external level converters; a 10kΩ pull-up is provided on the SCL line. The fixed I²C address is 0x53, and the module exposes pins for VIN, 3Vo (3.3V regulated output, up to 100mA), GND, SDA, and SCL, with an interrupt (INT) output available on some board variants. Unlike approximate UV sensors that infer UV index from visible light, the LTR390 performs genuine UV photodetection, and its raw UV reading can be converted to a UV index value through the manufacturer’s sensitivity formula in firmware.

The breakout measures approximately 25.8mm × 18mm (STEMMA QT / Qwiic form factor) and weighs around 4g with headers, though board dimensions vary slightly between suppliers. The sensor supports 13–20-bit effective resolution with programmable gain and integration time, and includes interrupt thresholds for event-driven operation. Typical applications include portable UV meters, outdoor UV detectors, germicidal lamp monitoring, weather stations, and light-sensitive automation in Arduino, Raspberry Pi, and ESP32 projects.