DS1302N

DS1302N is a Dallas/Maxim real-time clock (RTC) with a 3-wire serial interface and battery backup. It keeps calendar time (seconds–year) using a 32.768 kHz timebase and can run from VCC or VBAT, preserving time when power is lost. It also provides 31 bytes of battery-backed RAM for data storage. Interface is SPI-like: CE, SCLK, and I/O (plus VCC, VBAT, GND and oscillator pins for the 32 kHz crystal). Time/date registers, RAM, and a programmable square-wave output are accessible via the 3-wire bus. The “N” variant typically denotes a specific package or variant of the device. Common uses include clocks, calendars, dataloggers, and timer/event counters in microcontroller projects. Pros: simple 3-wire interface, fast reads/writes, continuous timekeeping on backup supply, optional trickle-charge circuit for the backup battery. Cons: not as accurate as temperature-compensated RTCs (e.g., DS3231); requires an external 32 kHz crystal and proper backup battery management; limited RAM (31 bytes).

Here are the key features of the DS1302N real‑time clock:
- Real-time clock/calendar with 32.768 kHz crystal input; keeps time in BCD.
- Battery-backed operation via VBAT; maintains clock and 31-byte NV RAM when main power is off.
- 31 bytes of non-volatile RAM for user data storage.
- Trickle-charge circuit to recharge a backup source (battery or capacitor) via external resistor/diode network.
- Three-wire serial interface: CE, SCLK, and I/O for register and RAM access.
- Programmable square-wave output (SQW/OUT) on a dedicated pin.
- Automatic power-switching between VCC and VBAT; low quiescent current in battery mode.
- Wide operating voltage range (typically 2.0 to 5.5 V).
- Available in 8-pin packages (DIP-8, SOIC-8).
Note: Actual RAM size and SQW options may vary with specific package/revision; consult the DS1302N datasheet for exact details.

- Pin count: 8 pins (DIP-8/SOIC-8).
- Function: Real-time clock/calendar IC with 32 kHz crystal input, 31 bytes of RAM, and battery backup (VBAT). Accessed via a 3-wire serial interface (CE, CLK, IO). Requires external crystal connected to X1/X2 pins and provides timekeeping registers (seconds, minutes, hours, day, date, month, year).

- Manufacturer: Dallas Semiconductor (Dallas).
- What kind of company: A U.S.-based semiconductor company that designs and manufactures integrated circuits (ICs). The Dallas brand was acquired by Maxim Integrated and is now part of Analog Devices.

DS1302N 的应用领域要点：
- 实时时钟与日历功能，嵌入式系统的时间基准
- 电池备用，掉电后仍保持时间和少量数据
- 数据记录与事件时间戳（环境监测、仪器仪表、数据采集等）
- 便携低功耗设备中的时间管理与日志记录
- 工业自动化与控制系统的排程与日志
- 安防/门禁系统的时间戳与事件记录
- POS/零售系统的交易时间记录与对账
- 测试仪器与实验设备的稳定时间源

DS1302N is an 8-pin RTC IC. It’s available in DIP‑8 (through‑hole) and 8‑pin surface‑mount packages such as SOIC‑8/SOP‑8; the common type is DIP‑8.