MAX6917
ObsoleteI²C-Compatible RTC with Microprocessor Supervisor, Alarm, and NV RAM Controller
Overview
- Real-Time Clock Counts
- Seconds, Minutes, Hours, Date, Month, Day of Week, and Year with Leap-Year Compensation Through 2099
- Fast (400kHz) I²C-Bus-Compatible Interface
- 96 x 8 Bits of RAM for Scratchpad Data Storage
- Uses Standard 32.768kHz, 6pF Load, Watch Crystal
- Single-Byte or Multiple-Byte (Burst Mode) Data Transfer for Read or Write of Clock Registers or RAM
- Battery Monitor and Low-Battery Warning Output
- Internal Default for Lithium Backup-Battery Testing
- Pins Available for Other Backup-Battery Testing Configurations
- Dual Power-Supply Pins for Primary and Backup Power
- Battery-On Output
- NV RAM Controller
- Chip-Enable Gating (Control of Active-Low CE with Reset and Power Valid)
- VOUT for SRAM Power
- Microprocessor Supervisor with Watchdog Input
- Programmable Time/Date Alarm Output
- Data Valid Bit (Loss of All Voltage Alerts User of Corrupt Data)
- Crystal-Fail Detect
- Reference Output Frequencies—1Hz and 32.768kHz
- Small, 20-Pin, QSOP Surface-Mount Package
The MAX6917 provides all the features of a real-time clock (RTC) plus a microprocessor (µP) supervisory circuit, NV RAM controller, and backup-battery monitor function. In addition, 96 x 8 bits of static RAM are available for scratchpad storage. The MAX6917 communicates with a µP through an I²C-bus-compatible serial interface.
The real-time clock/calendar provides seconds, minutes, hours, day, date, month, and year information. The end of the month date is automatically adjusted for months with fewer than 31 days, including corrections for leap years through 2099. The clock operates in either 24hr or 12hr format with an AM/PM indicator. A time/date-programmable alarm function is provided with an open-drain, active-low alarm output.
The µP supervisory circuit features an open-drain, active-low reset available in three different reset thresholds. A manual reset input and a watchdog function are included as well.
The NV RAM controller provides power for external SRAM from a backup battery plus chip-enable gating. The backup battery also provides data retention of the on-board 96 x 8 bits of RAM. An open-drain, active-low, battery-on signal alerts the system when operating from a battery.
The battery-test circuitry periodically tests the backup battery for a low-battery condition. An optional external resistor network selects different battery thresholds. A freshness seal prevents battery drain until the first VCC power-up.
The MAX6917 has a crystal-fail-detect circuit and a data-valid bit. The MAX6917 is available in a 20-pin QSOP package and is guaranteed to operate over the extended (-40°C to +85°C) temperature range.
Applications
- Digital Thermostats
- Fax Machines
- Industrial Control
- Intelligent Instruments
- Point-of-Sale Equipment
- Programmable Logic Controllers
Documentation
This is the most up-to-date revision of the Data Sheet.
Software Resources
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