As a low-power device widely used in electronic equipment, the DS1302 is centered on accurate real-time clock/calendar recording functions. It supports full-dimensional tracking of seconds, minutes, hours, days, weeks, months, and years, features automatic leap year compensation, and is compatible with 12/24-hour time formats. This article will comprehensively introduce the classic real-time clock chip DS1302 launched by Maxim Integrated.
Introduction to DS1302
Manufacturer of DS1302
DS1302 Pin Functions
Pin Number Pin Name Description 1 Vcc2 Second power input. The DS1302 is powered through this pin when Vcc2 is greater than Vcc1 + 0.2V. 2, 3 X1 and X2 Used to connect an external 32.768kHz crystal oscillator. 4 GND Ground 5 CE This pin is set to high level during read or write operations. 6 I/O (Data Line) This is a bidirectional data pin to the 3-wire interface. 7 SCLK (Serial Clock) Used to synchronize data movement on the serial interface. 8 Vcc1 Rechargeable power supply is connected to this pin.
DS1302 Package Dimensional Parameters
The DS1302 is commonly available in packages such as DIP (Dual In-line Package), with varying dimensional parameters for different packages.
| PNG | 5.9IN MIN | 5.9IN MAX | 10.9IN MIN | 10.9IN MAX | 14.9IN MIN | 14.9IN MAX | 19.9IN MIN | 19.9IN MAX |
|---|---|---|---|---|---|---|---|---|
| A IN | 0.100 | 0.190 | 0.100 | 0.240 | 0.100 | 0.310 | 0.100 | 0.340 |
| B IN | 0.100 | 0.290 | 0.100 | 0.410 | 0.100 | 0.610 | 0.100 | 0.640 |
| C IN | 0.120 | 0.340 | 0.120 | 0.340 | 0.120 | 0.540 | 0.120 | 0.340 |
| D IN | 0.300 | 0.540 | 0.250 | 0.450 | 0.210 | 0.320 | 0.200 | 0.340 |
| E IN | 0.300 | 0.320 | 0.300 | 0.320 | 0.300 | 0.320 | 0.300 | 0.320 |
| F IN | 0.150 | 0.140 | 0.100 | 0.130 | 0.120 | 0.120 | 0.120 | 0.140 |
| G IN | 0.060 | 0.110 | 0.070 | 0.100 | 0.080 | 0.110 | 0.080 | 0.110 |
| H IN | 2.10 | 3.10 | 2.70 | 3.10 | 2.90 | 3.10 | 2.90 | 3.10 |
| I IN | 0.900 | 0.940 | 0.900 | 0.940 | 0.900 | 0.940 | 0.900 | 0.940 |
| J IN | 0.090 | 0.092 | 0.090 | 0.092 | 0.090 | 0.092 | 0.090 | 0.092 |
| K IN | 0.010 | 0.021 | 0.010 | 0.021 | 0.010 | 0.021 | 0.010 | 0.021 |
DS1302 CAD Models
DS1302 Specifiction
| Specification Parameters | Details |
|---|---|
| Product Model | DS1302 |
| Description | IC RTC CLK/Calendar SER 8-DIP |
| Category | Integrated Circuit (IC), Clock/Timing - Real-Time Clock |
| Manufacturer | Maxim Integrated |
| Packaging | Tube |
| Component Status | Obsolete |
| Type | Clock/Calendar |
| Features | Year, NVSRAM, Trickle Charger |
| Memory Size | 31B |
| Time Format | HH:MM:SS (12/24-Hour) |
| Date Format | YY-MM-DD-dd |
| Interface | 3-Wire Serial |
| Base Part Number | DS1302 |
| Manufacturer Package Description | 0.300" DIP-8 |
| Status | Transition |
| Maximum Clock Frequency | 0.032 MHz |
| Information Access Method | Serial 3-Wire |
| JESD-30 Code | R-PDIP-T8 |
| JESD-609 Code | 00 |
| Number of Terminals | 8 |
| Number of Timers | 0.0 |
| On-Chip Data RAM Width | 8 |
| Minimum Operating Temperature | 0°C |
| Maximum Operating Temperature | 70°C |
| Package Body Material | Plastic/Epoxy |
| Package Code | DIP |
| Package Equivalent Code | DIP8.3 |
| Package Shape | Rectangular |
| Power Supply | 3/5 |
| Qualification Status | Unqualified |
| RAM (Words) | 31 |
| Subcategory | Timers or RTC |
| Maximum Supply Current | 1.28 mA |
| Nominal Supply Voltage | 5.0 V |
| Minimum Supply Voltage | 2.0 V |
| Maximum Supply Voltage | 5.5 V |
| Mounting Type | Through Hole |
| Technology | CMOS |
| Temperature Grade | Commercial |
| Terminal Finish | Tin/Lead (Sn/Pb) |
| Terminal Form | Through Hole |
| Terminal Spacing | 2.54 mm |
| Terminal Position | Dual |
| Minimum Time | Seconds |
| Volatile | Yes |
| Additional Features | Burst Mode RAM Data Transfer; Timekeeping Current = 0.3 µA |
DS1302 Features
The DS1302 is a widely - used real - time clock (RTC) chip with the following key features:
Comprehensive Time Tracking: Accurately records seconds, minutes, hours, day of the week, date (day of the month), month, and year. It has leap - year compensation that remains valid up to the year 2100, and can automatically adjust the date for months with fewer than 31 days.
Time Format Flexibility: Supports both 24 - hour and 12 - hour time formats, with an AM/PM indicator for the 12 - hour mode.
Battery - Backed RAM: Incorporates 31 bytes of non - volatile static RAM (NV SRAM). This memory can retain data even when the main power supply is disconnected, thanks to a backup battery (e.g., CR2032).
Simple Serial Interface: Uses a 3 - wire synchronous serial interface (including CE/RST, I/O, and SCLK pins). It can communicate with microcontrollers easily, and supports both single - byte data transfer and burst mode transfer (allowing up to 31 consecutive bytes to be read or written at once).
Dual Power Supply Pins: Equipped with two power pins (VCC for main power and VCC2 for backup power). When the main power fails, it automatically switches to the backup battery to ensure continuous timekeeping.
Wide Voltage Range & Low Power: Operates within a voltage range of 2.0V to 5.5V. It has extremely low power consumption — typically less than 300nA at 2.0V, and can maintain clock and RAM data with a power consumption of less than 1μW.
Programmable Trickle Charger: Features a programmable trickle charger for the backup battery (VCC2), which can intelligently supplement the battery’s power.
Compact Packaging: Available in 8 - pin DIP (Dual In - line Package) or SO (Small Outline) packages, taking up minimal space on the circuit board.
Temperature Adaptability:
- Commercial Grade: Operates within 0°C to 70°C, suitable for general - purpose applications.
- Industrial Grade (Optional): Can work in a wider temperature range of - 40°C to + 85°C, fitting for harsh industrial environments.
TTL Compatibility: Compatible with TTL levels (when VCC = 5V), making it easy to integrate into traditional 5V system designs.
Burst Mode Efficiency: The burst mode for RAM data transfer enables efficient reading and writing of large amounts of data.
Reliable Data Retention: Ensures seamless switching to the backup power supply during power outages, preventing loss of time and RAM data.
Broad Application Scope: Certified by organizations like Underwriters Laboratories (UL) and is widely used in consumer electronics, industrial control systems, and portable devices.
DS1302 Applications
| Scenario Requirements | Supporting Core Features of DS1302 | Typical Cases |
|---|---|---|
| Portable/battery-powered | Low power consumption (standby current < 300nA) + battery backup | Field weather stations, DIY portable clocks |
| Simplified main controller integration | 3-wire serial interface (CE/I/O/SCLK), reducing pin usage | 8051 microcontroller perpetual calendars, Arduino projects |
| Non-loss of data/time | 31-byte RAM + battery backup | Time attendance systems, industrial recorders |
| Long-term accurate timing | Leap year compensation (up to 2100) + basic precision guarantee | Electronic clocks, smart home timing |
Alternative solutions for DS1302
| Part Number | Description | Manufacturer |
|---|---|---|
| DS1202N | Real-time clock, volatile, 0 timers, CMOS, PDIP8 | Dallas Semiconductor |
| DS1202 | Real-time clock, volatile, 0 timers, CMOS, PDIP8 | Dallas Semiconductor |
| DS1302N+ | Real-time clock, CMOS, PDIP8, DIP-8 | Cypress Semiconductor |
| DS1302N | Real-time clock, volatile, 0 timers, CMOS, PDIP8, 0.300 inches, plastic, DIP-8 | Maxim Integrated Products |
| DS1302 | Real-time clock, volatile, 0 timers, CMOS, PDIP8, 0.300 inches, DIP-8 | Dallas Semiconductor |
Conclusion
To sum up, as a time-tested classic real-time clock chip, the DS1302 has gained a firm foothold in numerous fields such as consumer electronics, industrial monitoring, and embedded development, thanks to its accurate timekeeping capability, low-power characteristics, simple 3-wire interface design, and reliable dual power supply switching and data retention functions. Although the real-time clock chip market continues to see new products with higher precision and more functions (such as the DS3231 with temperature compensation), the DS1302, with its balanced performance, low cost, and user-friendly features, remains the preferred choice for small and medium-sized projects, teaching practices, and scenarios with basic timing needs. From driving daily timekeeping in electronic clocks, ensuring time synchronization in industrial equipment, to supporting the creative practices of makers, the DS1302 interprets the essence of "classic" through its technical characteristics—it may not be the most extreme choice in terms of parameters, but with its stability, ease of use, and strong adaptability, it continues to provide a reliable time reference for various electronic systems. For developers, understanding the working principle and application logic of the DS1302 is not only about mastering the use of a single chip, but also an excellent practice for in-depth learning of real-time clock technology, serial communication timing, and low-power design concepts. In the future, this chip will continue to play an irreplaceable role in the fields it excels in.
DS1302 Datasheet
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