DS1337

Overview

The DS1337 is a low-power I2C serial real-time clock and calendar. It tracks seconds, minutes, hours, day, date, month, and year with leap-year compensation valid through 2100. The device supports 12-hour and 24-hour formats. Full operation requires VCC between 1.8V and 5.5V, while timekeeping is maintained down to 1.3V. Active supply current is 150µA at 3.3V. Standby current is 1.5µA. Timekeeping current ranges from 425nA to 600nA with the oscillator enabled. Data retention current is 100nA with the oscillator disabled.

Feature Summary

• I2C Serial Interface supporting Standard (100kHz) and Fast (400kHz) modes
• Two programmable time-of-day alarms with interrupt outputs
• Programmable square-wave output selectable from 1Hz to 32.768kHz
• Oscillator Stop Flag (OSF) for battery failure detection

Applications

• Handheld devices such as GPS units and MP3 players
• Consumer electronics including set-top boxes and digital recorders
• Office equipment like fax machines and printers
• Medical devices such as glucometers and medicine dispensers
• Telecommunications infrastructure including routers and servers

Procurement Notes

Verify RoHS compliance status based on the specific ordering suffix. Suffixes ending in '+' indicate lead-free/RoHS-compliant devices. Suffixes ending in '#' denote RoHS-compliant devices that may include exempt lead. Confirm package type availability, as options include DIP-8, SOIC-8, µSOP-8, and SOIC-16 variants.

Selection Notes

Select the appropriate package variant based on board space and mounting requirements. The standard DS1337 requires an external 32.768kHz crystal. The DS1337C integrates the crystal within the 16-pin SO package. Ensure the design accommodates open-drain pull-up resistors for the SDA, SCL, INTA, and SQW/INTB pins.

Part Context

The DS1337 belongs to the Maxim Integrated RTC family designed for precise timekeeping in embedded systems. It provides a cost-effective solution for maintaining system time during power outages using a backup battery source connected to VCC.

Replacement Considerations

DS1337C: Integrated crystal version in 16-pin SO package.

FAQ

What is the minimum voltage required for timekeeping?

Timekeeping operation is maintained when VCC is as low as 1.3V.

How does the Oscillator Stop Flag function?

The OSF bit sets to logic 1 if the oscillator stops due to power loss or insufficient voltage, indicating potential data invalidity until cleared by software.

Can the DS1337 operate in both 12-hour and 24-hour modes?

Yes, the mode is selected via Bit 6 of the Hours register. Changing this bit requires reinitializing all hour values.