Microchip's MCP7941X series of low-power real-time clocks (RTC) uses digital timing compensation for an accurate clock/calendar, a programmable output control for versatility, a power sense circuit that automatically switches to the backup supply, and nonvolatile memory for data storage. Using a low-cost 32.768 kHz crystal, it tracks time using several internal registers. For communication, the MCP7941X uses the I2C™ bus.
The clock/calendar automatically adjusts for months with fewer than 31 days, including corrections for leap years. The clock operates in the 24-hour or 12-hour format with an AM/PM indicator and settable alarm(s) to the second, minute, hour, day of the week, date, or month. Using the programmable CLKOUT, frequencies of 32.768 kHz, 8.192 kHz and 4.096 kHz and 1 Hz can be generated from the external crystal.
Along with the onboard serial EEPROM and battery backed SRAM memory, a 64-bit protected space is available for a unique ID or MAC address to be programmed at the factory or by the end user. The device is fully accessible through the serial interface while Vcc is between 1.8 V and 5.5 V but can operate down to 1.3 V for timekeeping and SRAM retention only.
- Hours, minutes, seconds
- Day of the week, day, month, and year
- Dual alarms with single interrupt output using VCC or VBAT
- Programmable clock: 1 Hz to 32 KHz using VCC
- Digital trimming
- Range = -127 PPM to +127 PPM
- Resolution = 1 PPM
- Timestamp at battery switchover
Voltage and Current
- SRAM – 64 bytes
- EEPROM – 1 Kbit
- Unique ID – 64 bits
- VCC: 1.8 V to 5.5 V
- ICC: 400 µA
- VBAT: 1.3 V to 5.5 V
- IBAT: 700 nA
- Smart Energy - Smart Energy applications can use a real-time clock with a MAC address for wired and wireless communications with other devices.
- Utility metering - Digital trimming in the real-time clock can be used to perform software temperature compensation for more accurate time.
- Ethernet - EUI-48TM or EUI-64™ MAC address in the RTCC can provide any Ethernet enabled application with its own unique identification.
- LCD - Time of day and date from a real-time clock is regularly displayed on the LCD in many systems
- Thermostats - A highly integrated real-time clock device with memory, battery switchover, power-fail timestamp, and MAC address would be useful in many thermostats.
- Home appliance - A highly integrated real-time clock with many peripherals would be useful in home appliances.
- Medical - The development of electronic medical devices is nothing short of revolutionary. Microchip’s products and experience have helped hundreds of the world’s top medical device companies take their ideas from future vision to market reality.