DS1302SN

DS1302SN is a stand‑alone real‑time clock/calendar from Maxim/Dallas. It keeps accurate time with a 32.768 kHz crystal and can run from main power while keeping time on backup power (battery or supercap) when power is removed. It also provides 31 bytes of battery‑backed RAM for data logging and a built‑in trickle‑charger to maintain the backup supply.
Interface is a simple 3‑wire serial bus (CE, SCLK, IO). It’s not I2C or SPI; you enable the device with CE, then send an address byte (read/write) followed by data. The RTC stores time and date in BCD (seconds, minutes, hours, day, date, month, year) with optional 12/24‑hour formats. A control register enables features like a 1 Hz square‑wave output. The DS1302SN comes in an 8‑pin package suitable for many microcontroller projects.
Typical uses: clocks, timers, data loggers, and any embedded system needing reliable, battery‑backed timekeeping.

Concise features of DS1302SN:
- Real-time clock/calendar: seconds, minutes, hours, date, month, year, day-of-week; supports 12/24-hour mode; BCD data; leap-year handling; year 00–99 with century bit.
- 32.768 kHz crystal oscillator interface for accurate timekeeping.
- Battery backup (VBAT) with trickle-charge support to maintain time when VCC is off.
- Trickle-charge circuit: external diode and resistor to charge a rechargeable backup source.
- 31 bytes of battery-backed RAM for user data.
- Three-wire serial interface: CE, CLK, and I/O for fast read/write of time, RAM, and config.
- Programmable square-wave output (SQW/OUT) with selectable frequencies (including 1 Hz).
- Wide supply range and low power (works from ~2.0 V to 5.5 V; low current in battery mode).
- Package: DS1302SN in 8-pin format (DIP8/SOIC variants).

DS1302SN is an 8-pin Real-Time Clock (RTC) in a SOIC/DIP8 package. It uses a 3-wire serial interface (CE, SCLK, IO) to read/write time and RAM.
Pin functions (typical in DS1302SN):
- VCC: main supply
- GND: ground
- VBAT: battery backup input
- CE: chip enable for the 3‑wire interface
- SCLK: serial clock
- IO: bidirectional data line
- Two pins for the optional trickle-charge circuit (can be unused if trickle charging is not used)
The device also provides timekeeping registers plus 31 bytes of RAM.

- Manufacturer: Dallas Semiconductor (DS1302SN). Dallas Semiconductor later merged with Maxim Integrated, which was in turn acquired by Analog Devices.
- What kind of company: A semiconductor company that designs and manufactures integrated circuits (ICs), including real-time clocks.

DS1302SN is a serial RTC with 31-byte battery-backed NV RAM and a 3‑wire interface. Common applications:
- Embedded systems requiring accurate timekeeping (clock/calendar)
- Data loggers and telemetry with time stamps
- Alarm/timer functions in appliances and industrial controls
- Portable/handheld devices needing offline time data with backup memory
- Digital clocks, watches, and consumer electronics
- Time stamping in medical, security, and access-control systems

DS1302SN comes in an 8-pin package, available as DIP-8 (through-hole) and SO-8/SOIC-8 (surface-mount) variants.