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, CX FAIL-bar, 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 ALM-bar, 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.
Key Features
Applications/Uses
RTC Counts Seconds, Minutes, Hours, Date of the
Month, Month, Day of the Week, and Year, with
Leap Year Compensation Valid Up to 2100
31 Bytes of RAM for Scratchpad Data Storage
Uses Standard 32.768kHz, 6pF Load, Watch
Crystal
Programmable Time/Date, Open-Drain ALARM
Output (Status Can also Be Polled)
Chip Enable Gating (Control of CE-bar with Reset and
Power Valid)
OUT Pin for SRAM Power
µP Reset Output
Watchdog Input
Manual Reset Input with Push-Button Switch
Debounce
Independent Power-Fail and Reset Comparators
400kHz 2-Wire Interface
Single-Byte or Multiple-Byte (Burst Mode) Data
Transfer for Read or Write of Clock Registers or
RAM
Bus Timeout to Prevent Lockup of Malfunctioning
Bus Interface
Dual Power-Supply Pins for Primary and Backup
Power
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