Timekeeper Chip

Dallas Semiconductor's low-voltage serial timekeeping chip is claimed to be the first ultra-low voltage timekeeper with power monitoring circuitry and power-fail switches.

Previously, several parts were required to fill these capabilities in the 2.0 to 3.3 V ranges. Now the single-chip combination enables more efficient and cost-effective board designs.

The DS1672 is also the first low-voltage timekeeper to offer the option of an automatic switch to trickle charging.

Communicating with a processor over a two-wire interface, the DS1672's 32-bit counter counts seconds, from which a software algorithm computes time of day, week, month and year.

Silicon clocks are used in all kinds of computers and computerised systems; the DS1672's low-voltage operation is critical to battery-operated equipment such as mobile phones, GPS devices, palm-size computers and notebooks.

The device monitors power supplies for out-of-tolerance voltages. When an under-supply condition occurs, the DS1672 write-protects timekeeping data registers, resets the processor, and switches to backup power to prevent data corruption.

On low-power mode the oscillator maintains timekeeping down to 1.3 V, consuming less than 2000 nA.

When power supplies return to normal levels, the DS1672 holds the processor in reset for 250 ms while operating conditions stabilise.