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DS1302 Trickle-Charge RTC
Public Made by Adomby adom
Trickle-charge real-time clock with 31 bytes of RAM and a simple 3-wire interface.
3D Model
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Symbol & Footprint
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Datasheet
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README
markdownDS1302
Analog Devices · Real-Time Clock (RTC) · SOP-8 (208 mil)
The DS1302 is a trickle-charge real-time clock that counts seconds, minutes, hours, date, month, day of week, and year with leap-year compensation. It has 31 bytes of scratchpad RAM and communicates over a simple 3-wire (CE, SCLK, I/O) interface, with an optional trickle charger for a backup capacitor or cell.
Pinout
| Pin | Name | Type | Function |
|---|---|---|---|
| 1 | VCC2 | power_in | Primary power-supply pin in dual-supply configuration. The DS1302 operates from the larger of VCC1 or VCC2. When VCC2 is greater than VCC1 + 0.2V, VCC2 powers the DS1302; when VCC2 is less than VCC1, VCC1 powers the DS1302. Operating range 2.0V to 5.5V. |
| 2 | X1 | passive | Connection for a standard 32.768kHz quartz crystal. Internal oscillator is designed for a crystal with 6pF specified load capacitance. Can also be driven by an external 32.768kHz oscillator applied to X1 (with X2 floated). |
| 3 | X2 | passive | Second connection for the 32.768kHz quartz crystal. Left floating when an external oscillator drives X1. |
| 4 | GND | power_in | Device ground. |
| 5 | CE | input | Chip enable input. CE must be asserted high during a read or write to enable the control logic and shift register access. Has an internal 40k-ohm (typ) pulldown to ground. Previous datasheet revisions referred to this pin as /RST; functionality is unchanged. |
| 6 | I/O | bidirectional | Bidirectional serial data pin for the 3-wire interface. Push-pull output during read, high-impedance when CE is low, tri-stated on rising edge of SCLK. Has an internal 40k-ohm (typ) pulldown to ground. |
| 7 | SCLK | input | Serial clock input used to synchronize data movement on the 3-wire serial interface. Has an internal 40k-ohm (typ) pulldown to ground. |
| 8 | VCC1 | power_in | Low-power/battery-backup supply pin. In systems using the trickle charger the rechargeable energy source (e.g. supercap or lithium cell) is connected to this pin. UL-recognized reverse-charging protection is required when used with a lithium battery. |
Key specifications
| Parameter | Value |
|---|---|
| Type | Real-time clock (RTC) |
| Interface | 3-wire (CE, SCLK, I/O) |
| Timekeeping | Seconds to year, leap-year compensated to 2100 |
| RAM | 31 bytes scratchpad |
| Backup | Trickle-charge circuit for cap/cell |
| Supply voltage | 2.0 V to 5.5 V |
| Operating temperature | -40 C to 85 C |
Ordering variants
Same part, different packaging or reel option.
DS1302+DS1302N+DS1302S+DS1302SN+DS1302Z+DS1302ZN+
CAD (KiCad official)
- Symbol:
ds1302.kicad_sym - Footprint:
ds1302.kicad_mod - 3D model: SOP-8 208 mil (wide) body from KiCad
Package_SO/SOIC-8_5.3x5.3mm_P1.27mm. - 3D model files:
ds1302-etched.step/ds1302-etched.glbcarry the MPN laser-etched on the die in a toggleableAdom.LaserEtchgroup (Fusion-ready);ds1302.step/ds1302.glbare the bare package body.
Provenance
Data extracted from the manufacturer datasheet, not a distributor listing:
- Datasheet: Analog Devices datasheet (13 pp, sha256
fb627b436b89e8c9, retrieved 2026-08-17, tier: manufacturer) - Extractor:
ds2sf(Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate. - CAD: KiCad official libraries (CC-BY-SA 4.0).