The DS1390U-33+T&R with Real Time Clock Low-Voltage SPI/3-Wire RTCs with Trickle Charger is a Real Time Clock (RTC) product manufactured by Analog Devices. It provides enhanced timekeeping accuracy with built-in features including oscillator adjustment, external calibration, and manual calibration. It also includes a trickle charger, which helps maintain battery charge over extended periods of time, such as during power-off periods. Designed with low-voltage (2V) control options, the DS1390U-33+T&R RTCs elegantly meet the timekeeping requirements of industrial, automotive, and consumer applications. It also features SPI/3-Wire operation for high-speed, low-power communications with the host microcontroller. The device integrates the majority of support functions required for timekeeping and is offered in a small 5-pin, plastic DIP package.