DS1302S

DS1302S is a low‑power, real‑time clock/calendar IC from Maxim (Dallas) that keeps accurate time even when main power is off. It uses a simple three‑wire serial interface (CE, SCK, I/O) instead of I2C/SPI. It requires a 32.768 kHz crystal and provides timekeeping registers for seconds, minutes, hours, day, date, month, and year (with leap year handling). It also offers 31 bytes of battery‑backed RAM for user data. A trickle‑charge circuit lets a backup battery or supercapacitor power the clock during power loss. It supports a configurable square‑wave output (SQW) and operates from 2.0 to 5.5 V. Applications include timestamping, data logging, and event scheduling in embedded systems with or without mains power. It’s compact, easy to integrate, and does not require an MCU I2C/SPI peripheral to run.

Concise features of DS1302S:
- Real-time clock/calendar: tracks seconds, minutes, hours, date, month, day, year; supports 12/24-hour mode and leap-year handling.
- 32.768 kHz crystal oscillator input for accurate timekeeping.
- Battery-backed operation: VBAT preserves time (and RAM) when VCC is off.
- Trickle-charge circuit: recharges a backup battery or supercap via an external resistor network.
- 31 bytes of battery-backed RAM for data storage.
- 3-wire serial interface (CE, SCLK, IO) for simple read/write access to time, RAM and control registers.
- 8-pin package availability (DIP/SOIC).
- Low power consumption in battery-backed mode.

8 pins. It is a battery-backed real-time clock/calendar (RTC) with a 32.768 kHz crystal interface and a 3‑wire serial interface (CE, SCLK, I/O) for reading/writing time data; also provides a programmable square‑wave output (SQW/OUT) and a trickle-charge feature. Pinout typically includes VCC, GND, VBAT, X1, X2, CE, SCLK, and I/O.

- Manufacturer: Dallas Semiconductor (the DS1302S RTC).
- What kind of company: A U.S.-based semiconductor company that designed mixed-signal ICs for embedded systems (RTCs, memory, etc.). Dallas Semiconductor was acquired by Maxim Integrated, which is now part of Analog Devices.

DS1302S is an RTC with a 32kHz crystal, timekeeping, calendar, 31 bytes NV RAM, battery backup, and a trickle charger. Common applications:
- Real-time clock/calendar in microcontroller systems
- Time stamping and logging in data loggers and measurement systems
- Alarms and timed control
- Battery-backed timekeeping for portable/remote devices
- Digital clocks and consumer electronics
- IoT/automation, security systems, access control, and POS requiring timestamps

DS1302S is the surface-mount version, packaged in an 8-pin SOIC (SOP) package.