DS1302 Trickle-Charge RTC

@@ -0,0 +1,55 @@+# DS1302++**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++- `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`.++## Provenance++Data extracted from the manufacturer datasheet, not a distributor listing:++- **Datasheet:** [Analog Devices datasheet](https://www.analog.com/media/en/technical-documentation/data-sheets/DS1302.pdf) (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).++[Datasheet PDF](docs/ds1302-datasheet.pdf)

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