DS1393U-18+T&R

Real Time Clock Overview

The DS1393U-18+T&R is a low-voltage serial real-time clock (RTC) from Analog Devices/Maxim Integrated. It provides hundredths of a second, seconds, minutes, hours, day, date, month, and year information with automatic leap-year compensation valid up to the year 2100. The device utilizes a 3-wire synchronous serial interface and operates within an industrial temperature range of -40°C to +85°C. It features a programmable time-of-day alarm, power-fail detection circuitry that automatically switches to a backup supply, and trickle-charge capability for external batteries.

Real Time Clock Feature Summary

• 3-Wire Serial Interface: Communicates via SCLK, CE, and I/O pins; supports data rates up to 1MHz at 1.8V.
• Low-Voltage Operation: Designed for a nominal 1.8V supply (range 1.71V to 1.89V), with standby current typically 60µA to 100µA.
• Integrated Power Management: Includes power-fail detect and switch circuitry to maintain timekeeping on VBACKUP during primary power loss.
• Trickle Charger: Supports battery charging through selectable internal resistors (R1=250Ω, R2=2kΩ, R3=4kΩ).
• Reset/Pushbutton Function: Features an RST pin that acts as an active-low open-drain 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 voltage suffix '18' corresponds to the required 1.8V operating range (1.71V–1.89V) for your system design. Confirm the 'T&R' designation indicates tape-and-reel packaging suitable for automated assembly. Ensure the 3-wire interface compatibility matches your microcontroller's serial peripheral capabilities.

Real Time Clock Selection Notes

Select this component when a low-voltage 1.8V RTC is required alongside a 3-wire interface. Unlike the DS1390/DS1391 which use SPI, or the DS1392 which has separate SQW/INT pins, the DS1393 combines the interrupt/reset functionality into the RST pin while using the I/O line for data. Ensure the application does not require the high-speed 4MHz interface available in the 3.3V variants.

Real Time Clock Part Context

This part belongs to the DS1390–DS1394 family of low-voltage RTCs. The DS1393 specifically differentiates itself by using a 3-wire interface and featuring an integrated RST output/debounced input pin, whereas the DS1392 uses the same interface but provides separate SQW and INT outputs. All devices in the series share similar calendar functions and package options (µSOP-10).

Real Time Clock Replacement Considerations

The DS1392U-18+ is a functional alternative within the same family if separate Square Wave and Interrupt pins are preferred over the combined RST function. The DS1391U-18+ offers a similar RST feature but utilizes a standard 4-wire SPI interface instead of 3-wire.