DS1392U-33+

Real Time Clock Overview

The DS1392U-33+ is a low-voltage real-time clock (RTC) and calendar from Analog Devices/Maxim Integrated, housed in a 10-pin µSOP package. It provides hundredths of seconds, seconds, minutes, hours, day, date, month, and year information with automatic leap-year compensation valid through 2100. The device communicates via a 3-wire synchronous serial bus and features separate interrupt (INT) and square-wave (SQW) outputs. It includes power-fail detection circuitry that automatically switches to a backup supply when VCC drops below the power-fail threshold.

Real Time Clock Feature Summary

• 3-Wire Serial Interface: Communicates using SCLK, CE, and I/O pins for address and data transfer.
• Separate Interrupt and Square Wave Outputs: Dedicated INT pin for CPU interrupts and SQW pin for programmable frequencies (32.768kHz, 8.192kHz, 4.096kHz, or 1Hz).
• Power-Fail Detection and Switching: Temperature-compensated voltage reference monitors VCC; automatically disables bus interface and switches to VBACKUP upon power failure.
• Trickle-Charge Capability: Supports trickle charging of backup sources with selectable current-limiting resistors (R1=250Ω, R2=2kΩ, R3=4kΩ).

Real Time Clock Applications

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

Real Time Clock Procurement Notes

Verify component authenticity through authorized distributors or direct manufacturer channels. Confirm RoHS compliance status and check for end-of-life notifications, as older Maxim Integrated RTC families may have discontinued variants. Ensure ordering suffixes match required voltage ranges and packaging types.

Real Time Clock Selection Notes

Select the DS1392U-33+ when a 3-wire interface is preferred over SPI or I2C. This variant supports a VCC range of 2.97V to 5.5V. Note that unlike the DS1390/DS1394, this model does not support an RST output/debounced input function; it utilizes dedicated INT and SQW pins instead.

Real Time Clock Part Context

The DS1392U-33+ belongs to the DS1390–DS1394 family of low-voltage RTCs. While the DS1390, DS1391, and DS1394 use an SPI-compatible 4-wire interface, the DS1392 and DS1393 utilize a 3-wire synchronous serial bus. All devices in the series share similar timekeeping capabilities and power management features but differ in interface protocols and specific pin configurations.

Real Time Clock Replacement Considerations

Public confirmed substitute part numbers are not available in the provided documentation.