DS1393U-18+

Real Time Clock Overview

The DS1393U-18+ is a low-voltage serial real-time clock (RTC) and calendar manufactured by Analog Devices Inc./Maxim Integrated. It provides hundredths of a second, seconds, minutes, hours, day, date, month, and year information with leap-year compensation valid up to the year 2100. The device utilizes a 3-wire synchronous serial interface for data transfer. Key features include one programmable time-of-day alarm, trickle-charge capability for backup batteries, and automatic power-fail detection with switching to a backup supply. The part operates within an industrial temperature range of -40°C to +85°C and is housed in a 10-pin µSOP package.

Real Time Clock Feature Summary

• 3-Wire Serial Interface: Communicates via SCLK, CE, and I/O pins.
• Real-Time Clock: Counts hundredths of seconds, seconds, minutes, hours, day, date, month, and year with leap-year correction.
• Power Management: Includes power-fail detect circuitry that automatically switches to VBACKUP when VCC drops below the power-fail voltage (VPF).
• Trickle Charger: Supports trickle charging of backup sources using selectable current-limiting resistors.
• Reset Functionality: Features an RST pin that acts as both a reset output and a debounced pushbutton input.

Real Time Clock Applications

• Hand-Held Devices
• GPS/Telematics Devices
• Embedded Time Stamping
• Medical Devices

Real Time Clock Procurement Notes

Verify the specific ordering suffix 'U-18+' against the manufacturer's datasheet to confirm the 1.71V to 1.89V supply voltage range and 3-wire interface configuration. Ensure compatibility with system power rails before procurement. Check for end-of-life status or alternative recommendations from Analog Devices if long-term availability is required.

Real Time Clock Selection Notes

Select the DS1393U-18+ for applications requiring a 3-wire interface rather than SPI. The '-18' suffix indicates operation at a nominal 1.8V supply (1.71V to 1.89V). If SPI interface is preferred, consider the DS1390 series. If higher voltage operation (3.0V or 5.5V) is needed, select the '-3' or '-33' suffix variants respectively. Ensure the design accommodates the 10-pin µSOP package constraints.

Real Time Clock Part Context

The DS1393 is part of the DS1390–DS1394 family of low-voltage RTCs. While the DS1390, DS1391, and DS1394 use an SPI-compatible bus, the DS1392 and DS1393 utilize a 3-wire synchronous serial bus. The DS1393 specifically combines the 3-wire interface with an RST output/debounced input pin, distinguishing it from the DS1392 which has separate SQW and INT outputs.

Real Time Clock Replacement Considerations

Public confirmed substitute part numbers are not available in the provided documentation. Consider checking the manufacturer's website for recommended products or cross-reference with other devices in the DS139x family if interface or voltage requirements can be adapted.