DS1284/DS1286 is an integrated clock, alarm, watchdog timer and timer interval in a 28-pin JEDEC DIP and encapsulated DIP package. It contains an embedded lithium energy source and a quartz crystal, which eliminates the need for any external circuitry. DS1284 requires an external quartz crystal and a VBAT source, which could be a lithium battery. Data contained within 64 8-bit registers can be read or written in the same manner as byte-wide static RAM. Data is maintained in the watchdog timekeeper by intelligent control circuitry that detects the status of VCC and write protects memory when VCC is out of tolerance. The lithium energy source can maintain data and real time for over 10 years in the absence of VCC. Watchdog timekeeper information includes hundredths of seconds, seconds, minutes, hours, day, date, month, and year. The date at the end of the month is automatically adjusted for months with fewer than 31 days, including correction for leap year. The DS1284/DS1286 operate in either 24-hour or 12- hour format with an AM/PM indicator. The devices provide alarm windows and interval timing between 0.01 seconds and 99.99 seconds. The real-time alarm provides for preset times of up to one week.
The DS1284 and DS1286 are self‑contained watchdog timekeepers that combine a real‑time clock, alarm, watchdog timer and interval timer in a 28‑pin JEDEC DIP or PLCC package. The DS1286 includes an embedded lithium energy source and quartz crystal, while the DS1284 requires an external crystal and battery.
The datasheet provides a complete description of the device operation, pin assignments, electrical ratings, timing parameters, and package dimensions. It also lists the 64 eight‑bit registers, 50 bytes of user non‑volatile RAM, and the command register functions needed for integration into a system.
| Operating Temperature Range (Industrial) | -40°C to +85°C |
|---|---|
| Operating Temperature Range (Commercial) | 0°C to +70°C |
| Power‑Supply Voltage (VCC) | 4.5 V – 5.5 V (typ. 5.0 V) |
| Battery Input Voltage (VBAT) | 2.4 V – 3.5 V (typ. 3.0 V) |
| User Non‑Volatile RAM | 50 bytes |
| Register Count | 64 eight‑bit registers |
| Accuracy | ±1 minute/month at +25°C |
The VCC supply voltage can range from 4.5 V to 5.5 V, with a typical value of 5.0 V.
The device provides 50 bytes of user non‑volatile RAM.
Industrial operation is supported from –40 °C to +85 °C.
Any access to watchdog registers C or D reinitializes the watchdog timer and clears the watchdog flag.