General Description

The MCP7940N Real-Time Clock/Calendar (RTCC)

tracks time using internal counters for hours, minutes,

seconds, days, months, years, and day of week.

Alarms can be configured on all counters up to and

including months. For usage and configuration, the

MCP7940N supports I2C communications up to

400 kHz.

The open-drain, multi-functional output can be

configured to assert on an alarm match, to output a

selectable frequency square wave, or as a general

purpose output.

The MCP7940N is designed to operate using a

32.768 kHz tuning fork crystal with external crystal

load capacitors. On-chip digital trimming can be used

to adjust for frequency variance caused by crystal

tolerance and temperature.

SRAM and timekeeping circuitry are powered from the

back-up supply when main power is lost, allowing the

device to maintain accurate time and the SRAM

contents. The times when the device switches over to

the back-up supply and when primary power returns

are both logged by the power-fail time-stamp.

Timekeeping Features

• Real-Time Clock/Calendar (RTCC):

- Hours, Minutes, Seconds, Day of 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

• Versatile Output Pin:

- Clock output with selectable frequency

- Alarm output

- General purpose output

• Power-Fail Time-Stamp:

- Time logged on switchover to and from Battery mode

Low-Power Features

• Wide Voltage Range:

- Operating voltage range of 1.8V to 5.5V

- Backup voltage range of 1.3V to 5.5V

• Low Typical Timekeeping Current:

- Operating from VCC: 1.2 μA at 3.3V

- Operating from battery backup: 925 nA at 3.0V

• Automatic Switchover to Battery Backup

MCP7940NT-I/ST属于集成电路（IC） > 实时时钟。微芯科技股份有限公司制造生产的MCP7940NT-I/ST实时时钟实时时钟 (RTC) 为几乎所有需要保持精确时间的电子设备提供时间和/或日期信息。时钟类型有二进制计数器、时钟/日历/监控器、历时计时器、幻时钟芯片、便携式系统控制器、温度记录器、时间事件记录器和计时器时钟外设。其包含 2 B 至 2 MB 不等的存储器，接口选项有 I2C、并行、串行、SPI、1 线式、2 线式、3 线式和 4 线式。