DS1306E+

Real Time Clock Overview

The DS1306E+ is a serial alarm real-time clock (RTC) manufactured by Analog Devices Inc./Maxim Integrated. It provides a full binary coded decimal (BCD) clock/calendar with leap-year compensation valid up to 2100. The device includes 96 bytes of battery-backed NV RAM for data storage and two programmable time-of-day alarms. It operates on a single supply voltage ranging from 2.0V to 5.5V and supports both Motorola SPI modes 1 and 3, as well as a standard 3-wire interface. The component is housed in a 20-pin TSSOP package and functions within a commercial temperature range of 0°C to +70°C.

Real Time Clock Feature Summary

• Dual power supply pins (VCC1, VCC2) and a dedicated battery input (VBAT) enable flexible backup configurations using non-rechargeable batteries or rechargeable sources like supercapacitors.
• Supports Motorola SPI (Modes 1 and 3) and standard 3-wire serial interfaces, allowing burst mode reading/writing of successive addresses in the clock and RAM.
• Includes two programmable time-of-day alarms that can generate interrupts based on combinations of seconds, minutes, hours, and day of the week.
• Features an interface logic power-supply pin (VCCIF) to drive SDO and 32kHz outputs to levels compatible with 3V logic in mixed-supply systems.

Real Time Clock Applications

• Systems requiring precise timekeeping with automatic date adjustment for months and leap years.
• Applications needing secure data storage via 96-byte battery-backed NV RAM.
• Devices utilizing programmable alarms for scheduled interrupt generation.
• Mixed-voltage systems requiring easy interfacing between 5V RTC logic and 3V microcontrollers.

Real Time Clock Procurement Notes

Verify the specific suffix 'E+' indicates a lead-free/RoHS-compliant package in the 20-pin TSSOP format. Confirm the operating temperature range is commercial (0°C to +70°C), distinct from industrial variants which carry different suffixes. Ensure the serial interface mode selection pin (SERMODE) is correctly configured for either SPI or 3-wire communication during integration.

Real Time Clock Selection Notes

Select the DS1306E+ when a 20-pin surface-mount package is required for space-constrained designs. Choose this model over DIP versions if PCB area is limited. Verify that the system power supply falls within the 2.0V to 5.5V range. Consider the industrial temperature variant (DS1306EN+) if operation below 0°C or above 70°C is necessary.

Real Time Clock Part Context

The DS1306 series is part of Maxim Integrated's line of serial alarm real-time clocks. The 'E' suffix denotes the 20-pin TSSOP package, while the '+' suffix signifies RoHS compliance. This component serves as a low-power timekeeping solution with integrated memory, distinguishing it from basic RTCs that lack NV RAM or dual-alarm capabilities.

Real Time Clock Replacement Considerations

Direct replacements include other DS1306 variants such as DS1306N (DIP package) or DS1306EN (Industrial temp, TSSOP). For package changes, verify pin compatibility. Cross-family alternatives may require interface adaptation due to differences in register maps or power management features.

Real Time Clock FAQ

How does the DS1306 handle power switching between primary and backup supplies?

The device switches to battery backup (VBAT) when VCC1 falls below VBAT + 0.2V. In dual-supply configurations with a rechargeable source on VCC2, it powers from the higher voltage source without write-protecting itself automatically.

What is the function of the VCCIF pin?

VCCIF provides the logic-high level for the SDO and 32kHz output pins, allowing the DS1306 to interface easily with 3V logic systems even when powered by higher voltages.

Can the DS1306 be used with a supercapacitor for backup?

Yes, Configuration 2 in the datasheet illustrates using a rechargeable energy source like a supercapacitor connected to VCC2, supported by a programmable trickle charger circuit.