MCP79411T-I/SN IC

Technical Specifications of MCP79411T-I/SN

Datasheet	MCP79411T-I/SN datasheet
Category	Integrated Circuits (ICs)
Family	Clock/Timing – Real Time Clocks
Manufacturer	Microchip Technology
Series	–
Packaging	Tape & Reel (TR)
Part Status	Active
Type	Clock/Calendar
Features	Alarm, Leap Year, Square Wave Output, SRAM, Unique ID
Memory Size	64B
Time Format	HH:MM:SS (12/24 hr)
Date Format	YY-MM-DD-dd
Interface	I2C, 2-Wire Serial
Voltage – Supply	1.8 V ~ 5.5 V
Voltage – Supply, Battery	1.3 V ~ 5.5 V
Current – Timekeeping (Max)	1.2μA @ 3.3V
Operating Temperature	-40°C ~ 85°C
Mounting Type	Surface Mount
Package / Case	8-SOIC (0.154″, 3.90mm Width)
Supplier Device Package	8-SOIC

MCP79411T-I/SN General Description

Hours, minutes, seconds, days, months, years, and days of the week are all kept track of by the MCP7941X RTCC’s internal clocks. All time intervals, from seconds to months, can have alarms set for them. The MCP7941X can communicate through I2C at speeds up to 400 kHz, making it suitable for use and setup. The open drain, the multipurpose output, can assert on an alarm match, produce a square wave at a frequency of your choosing, or serve as a general-purpose output. The MCP7941X is meant to run on a tuning fork crystal with a frequency of 32.768 kHz and external crystal load capacitors.

On-chip digital trimming can be employed to compensate for frequency variation due to crystal tolerance and temperature. When the main power goes off, the device’s SRAM and timekeeping circuits remain operational thanks to the backup battery. The power-fail timestamp records the moment that the device begins using the secondary power source and again when the primary power is restored. The MCP7941X has a 1 Kbit inbuilt nonvolatile EEPROM that may be encrypted via software. Safely storing a unique identifier or other sensitive data, the additional 64 bits of nonvolatile memory are writable only after an unlock sequence. The MCP79411 and the MCP79412 come with EUI-48 and EUI-64 addresses already programmed into them. Programming tailored to your specific needs is also available.

Timekeeping Features

Real-Time Clock/Calendar (RTCC)

• Hours, minutes, seconds, day of the week, day, month, year
• Leap year compensated to 2399
• 12/24-hour modes

Oscillator for 32.768 kHz Crystals

• Optimized for 6-9 pF crystals

 On-Chip Digital Trimming/Calibration

• ±1 ppm resolution
• ±129 ppm range

Dual Programmable Alarms

Power-Fail Timestamp

Time logged on the switchover to and from Battery mode

Functional Description

The MCP7941X is a Real-Time Clock and Calendar with a high level of integration (RTCC). The current time is kept track of in seconds, minutes, hours, and days of the week, day, month, and year by utilizing an onboard oscillator that consumes very little power. The MCP7941X has 64 bytes of general-purpose SRAM, 1 kbit of EEPROM, and 8 bytes of protected EEPROM. Interrupts can be generated at precise periods thanks to the combination of two alarm modules, which also offer flexible comparison possibilities.

The use of digital trimming can compensate for the errors that are inherent to crystals. When the primary power source fails, the MCP7941X automatically switches to the backup power supply using the backup supply input and an integrated power switch. This will allow the current time and the contents of the SRAM to continue functioning normally. When primary power is lost, the timestamp module records the time, and when it is restored, it displays the time. To access any of the modules that the MCP7941X has to offer, one must first access the RTCC configuration registers and the STATUS registers.

Memory Organization

Four distinct memory blocks are included in the MCP7941X. These are the RTCC registers, the general purpose SRAM, the 1 Kbit EEPROM with software write-protect, and the protected EEPROM. The address space used by the RTCC records and the SRAM is the same, and both can be accessed using the control byte represented by the value ‘1101111X’. The EEPROM sections are located in their own distinct address space, which can only be accessed using the control byte represented by the value ‘1010111X’.

Oscillator Configuration

Depending on the application, the MCP7941X can function in either an external crystal oscillator configuration or an external clock input oscillator configuration.

External Crystal

The crystal oscillator circuit on the MCP7941X was developed to function with a standard tuning fork crystal operating at 32.768 kHz and matching external load capacitors. These components are required for proper operation. Because it uses external load capacitors, the MCP7941X can accommodate a diverse range of crystals. Suitable crystals have a load capacitance (CL) value in the 6-9 pF. Using crystals with a load capacitance of 12.5 pF or higher is not suggested.

Layout Considerations

It is recommended that the oscillator circuit be installed on the side of the board parallel to the device. Position the oscillator circuit so that it is close to the oscillator pins. On the same side of the circuit board as the oscillator itself, the load capacitors should be positioned to be adjacent to the component. To prevent the oscillator circuit from being affected by other circuits, enclose it in a copper pour that has been grounded. The grounded copper pour ought to have a connection established straight to VSS. Inside the ground pour, you should not run any signal or power traces at any time. Additionally, if you use a board with two sides, you should avoid placing any traces on the side of the panel where the crystal is located.

Timekeeping

The MCP7941X utilizes an external 32.768 kHz crystal or clock source to keep track of the current time and date. Each of the following: seconds, minutes, hours, days of the week, dates, months, and years are recorded in their registers. The MCP7941X is programmed to make automatic adjustments for months with fewer than 31 days and to account for leap years beginning in 2001 and continuing until 2399. A number consisting of just two digits is used to store the year. There is support for both the 12-hour and 24-hour time formats, and the 12/24 bit is used to make the selection. The value of each day of the week counts from one to seven, with increments occurring at midnight; the representation is up to the individual user (i.e., the MCP7941X does not require 1 to equal Sunday, etc.).

Binary-coded decimal (BCD) values are used to store all of the time and date information that is contained inside the registers. Despite being powered by the backup supply, the MCP7941X will not lose track of the current time or date that it is displaying. When reading from the timekeeping registers, they are buffered so that errors caused by the rollover of counters are avoided. The following events are responsible for the updating of the buffers:

• When the RTCC registers (locations 0x00 to 0x1F) are read, the address of the registers will roll over from 0x1F to 0x00.
• It is best to read the timekeeping registers in a single operation to make the most of the onboard buffers and prevent rollover problems.

Conclusion

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