DALLAS Semiconductor, represented by Arrow Electronics , has introduced the DS139x (DS1390, DS1391, DS1392, and DS1393) family of 3-/4-wire or SPI-bus real-time clocks.
These clocks feature automatic power switching, trickle-charge output, alarm, microprocessor reset, square-wave output or periodic interrupt.
The DS139x ICs are available in a small 10-pin SOP package, the smallest footprint in the industry when compared to other real-time clocks with a SPI or 3-wire interface.
Ideal applications for these new RTCs are handheld equipment that can take advantage of all the DS139x's features. Potential applications include a portable POS terminal, hand-held medical devices like a glucose tester, and even a GPS system.
The DS1390 and DS1391 use the 4-wire or SPI bus interface, while the DS1392 and DS1393 use the 3-wire interface. All four parts monitor Vcc and, when a power-fail occurs, they write-protect the internal registers and switch to backup power to prevent data corruption.
In low-power mode, the oscillator maintains timekeeping down to 1.3V, consuming less than 1 microamps of current. A built-in trickle-charging circuit backs up the DS139x with a super cap or rechargeable battery.
The remaining available pins are configured in a combination of microprocessor reset, square-wave output, or periodic interrupt for even more added value in the small 3mm x 5mm package.
The DS139x are rated for operation over the industrial temperature range (-40 degrees Celsius to +85 degrees Celsius).