DS1305

Overview

The DS1305 is a serial alarm real-time clock manufactured by Analog Devices Inc./Maxim Integrated. It provides binary coded decimal (BCD) timekeeping for seconds, minutes, hours, date, month, and year with leap-year compensation valid through 2100. The device includes 96 bytes of battery-backed NV RAM for data storage. It supports SPI Modes 1 and 3 or standard 3-wire interfaces via the SERMODE pin. Operating from 2.0V to 5.5V, it features dual power supply pins for primary and backup sources, along with a programmable trickle charger. Timekeeping current ranges from 25.3µA to 81µA at 2V–5V.

Feature Summary

• Dual Power Supply Pins: Supports primary/backup supplies and optional trickle charging for rechargeable sources.
• Serial Interfaces: Compatible with SPI Modes 1/3 or standard 3-wire communication via SERMODE pin selection.
• Alarm Functionality: Two programmable time-of-day alarms with interrupt outputs INT0 and INT1.
• Leap-Year Compensation: Automatically adjusts for months with fewer than 31 days up to the year 2100.

Applications

• Systems requiring precise calendar and clock tracking with battery backup.
• Mixed-supply environments utilizing VCCIF for 3V logic compatibility.
• Data logging applications leveraging the 96-byte NV RAM storage.

Procurement Notes

Verify the specific package variant required, as the DS1305 family includes DIP-16 and TSSOP-20 options. Confirm temperature range specifications; the base model operates from 0°C to +70°C, while industrial variants extend to -40°C to +85°C. Ensure ordering suffixes match the desired interface mode configuration and lead-free compliance status.

Selection Notes

Select the DIP-16 package for through-hole mounting or TSSOP-20 for surface-mount applications. Choose the industrial temperature grade if operation below 0°C is required. Verify that the system design accommodates the dual power supply architecture (VCC1/VCC2) or single battery configuration. Ensure the microcontroller supports either SPI or 3-wire protocols based on the SERMODE pin connection.

Part Context

The DS1305 belongs to the Maxim Integrated RTC family, designed for low-power timekeeping. It shares functional similarities with the DS1306 but differs in interface flexibility and package options. The component is part of a broader series including the DS1307, which utilizes I2C instead of SPI/3-wire interfaces.

Replacement Considerations

DS1305N+ (Industrial Temp Range)

FAQ

How is the serial interface mode selected?

The interface mode is determined by the SERMODE pin. Connecting SERMODE to VCC selects SPI communication, while connecting it to GND selects the standard 3-wire interface.

What is the function of the VCCIF pin?

The VCCIF pin serves as the interface logic power-supply input. It allows the SDO and PF pins to drive signals compatible with lower voltage logic levels, such as 3V systems.

Can the DS1305 charge a backup battery?

Yes, the device includes a programmable trickle charger. It can charge rechargeable energy sources like super capacitors or rechargeable batteries connected to the VCC2 pin.