DS1302S+

DS1302S+ is a low‑cost real‑time clock/calendar IC with battery backup. It keeps time with a 32.768 kHz crystal and continues running when main power is off, using VBAT (backup battery or supercap) and a trickle‑charge circuit.
Key points:
- Interface: 3‑wire serial (CE, CLK, IO) — not I2C or SPI.
- Time registers: seconds, minutes, hours, day, date, month, year (with leap year handling).
- RAM: about 31 bytes of general‑purpose NV RAM.
- Power: VCC 2.0–5.5 V; VBAT for backup.
- Crystal: requires an external 32.768 kHz crystal.
- Package: common 8‑pin packages (DIP/SO).
Pros: simple, inexpensive, easy to wire to microcontrollers; good for basic timekeeping and timestamping with battery backup.
Cons: less precise than dedicated high‑accuracy RTCs; limited RAM; uses a non‑I2C/SPI protocol.
Common uses: clock displays, data logging, time stamping in embedded projects. For exact pinouts and timing commands, refer to the DS1302S+ datasheet.

DS1302S+ is a 3‑wire RTC (32.768 kHz) with battery-backed RAM. Direct pin‑for‑pin substitutes are limited. Common equivalents (functionally similar, may require different interfaces or footprints):
- DS1302/DS1302S (same family)
- DS1307 (I2C RTC)
- DS3231 / DS3232 (I2C, higher accuracy, built‑in crystal)
- PCF8563 (I2C)
- MCP7940N / MCP7942N (I2C, battery RAM)
Note: choose based on interface compatibility; 3‑wire substitution may need a bridge or rework.

Key features of the DS1302S+ real-time clock:
- Real-time clock/calendar: seconds, minutes, hours, day, date, month, year; 12/24-hour mode; leap-year aware; valid through year 2100.
- 32 kHz crystal oscillator input for timekeeping.
- 31 bytes of battery-backed RAM (NV RAM) for data storage.
- 3-wire serial interface: RST, CLK, IO (read/write time, date and RAM).
- VBAT backup with automatic switchover to maintain time when VCC is off.
- Trickle-charge capability to recharge a rechargeable battery (NiCd/NiMH) from VCC via external resistors/diodes.
- Wide operating voltage: typically 2.0V to 5.5V; low power overall.
- Optional square-wave/ SQW output (configurable, e.g., 1 Hz or 32 kHz) for timing signals.
- Package options: common 8-pin DIP/SOIC variants; suitable for hobbyist and embedded use.
Note: exact pinout and voltage ranges may vary by package/revision; consult the datasheet for specifics.

DS1302S+ is an 8-pin RTC with a 3-wire interface.
Pinout (DIP/SOP-8):
- Pin 1: CE – Chip Enable (active high)
- Pin 2: I/O – Bidirectional data I/O
- Pin 3: SCLK – Serial clock
- Pin 4: GND – Ground
- Pin 5: VCC – Main supply
- Pin 6: X1 – Crystal oscillator input
- Pin 7: X2 – Crystal oscillator output
- Pin 8: VBAT – Backup battery input (powers RTC when VCC is off)
Interface uses CE, SCLK, and I/O to read/write registers; X1/X2 connect to a 32.768 kHz crystal; VBAT allows battery backup.

- Manufacturer: Dallas Semiconductor (the DS1302S+ originally came from Dallas Semiconductor; the company later became part of Maxim Integrated, which is now under Analog Devices).
- What kind of company: A semiconductor company that designs and manufactures integrated circuits (ICs), including real‑time clocks, memory, and other ICs.

DS1302S+ is a low-cost real-time clock with battery-backed RAM and a simple 3-wire interface. Common application areas:
- Real-time clock/calendar for microcontrollers (timekeeping during power loss)
- Data loggers and sensors (timestamped records)
- Alarms, timers, and scheduled events in consumer electronics (clocks, appliances)
- Event logging for security/access control
- Automotive/industrial time-stamping and scheduling
- IoT/remote devices requiring local timekeeping with low pin count and power efficiency

DS1302S+ is an 8-pin RTC available in both DIP-8 and SOIC-8 (SOP-8) packages.