I²C-Compatible Real-Time Clocks with µP Supervisor and NV RAM Controller

All versions are No Longer Available.

The MAX6909/MAX6910 are I²C-compatible real-time clocks (RTCs) with a microprocessor supervisor, optional trickle charger (MAX6910 only), backup power source, and NV RAM controller. The MAX6909/MAX6910 provide alarm outputs to indicate a crystal failure, a switchover to battery power, and time and date indication. The NV RAM is 31 bytes of static RAM that are available for scratchpad storage. The MAX6909/MAX6910 are controlled through a 2-wire serial bus.

The real-time clock/calendar provides seconds, minutes, hours, day, date, month, and year information. The date is automatically adjusted for months with fewer than 31 days, including corrections for leap year up to the year 2100. The clock operates in either the 24-hour or 12-hour format with an AM/PM indicator. A time/date-programmable ALARM output completes the features list for the real-time clock section of the MAX6909/MAX6910. The alarm function can also be used in a polled mode by periodically reading the alarm out status bit in the minutes register. A crystal fail output, active-low CX FAIL, indicates loss of accurate timekeeping due to crystal problems.

A built-in µP supervisor with an open-drain reset ensures the µP powers up in a known state. A reset threshold is available for 3V or 3.3V supplies. The piezo transducer output, PZT, is register selectable for one of four frequencies, can be turned on and off through a register bit, or selected to go on when the active-low ALM, alarm output, goes active.

The MAX6909/MAX6910 are available in a 20-pin QSOP package and operate over the -40°C to +85°C temperature range.

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