MCP7940NT-E/SN

The MCP7940NT-E/SN is Microchip Technology’s I2C real‑time clock (RTC) with a 32.768 kHz timebase and battery‑backup capability. It keeps accurate time and calendar data (seconds–year) even when main power is removed, making it ideal for clocks, logging, and timestamps.
Key features:
- I2C 2‑wire interface (Fast mode up to 400 kHz) with a selectable address.
- Timekeeping registers for seconds, minutes, hours, day, date, month and year; alarms and status/interrupt flags.
- Optional square‑wave output and a trickle‑charge circuit to maintain a backup supply from a battery or capacitor.
- Non‑volatile RAM for user data.
- Low power consumption; available in an extended‑temperature variant (E: −40°C to +125°C).
- Packaging: SN suffix (Tape & Reel) for SMT.
Typical uses: embedded systems requiring persistent, accurate timekeeping—clocks, event logging, timestamping, data acquisition, and automotive/industrial devices.
Note: Check the latest datasheet for exact RAM size, register map, and electrical specs.

Possible equivalents (I2C RTCs with NV memory) to MCP7940NT-E/SN include:
- DS1307 (Dallas/Maxim)
- DS3231 (Maxim)
- NXP PCF8563 (RTC/Calendar with RAM)
- STMicroelectronics M41T00/M41T02 (RTC with NV RAM)
Note: pinouts, RAM size, and accuracy differ; verify compatibility (voltage, backup battery, and timing) for your design.

Key features of MCP7940NT-E/SN:
- I2C two-wire interface (up to fast-mode) for communication with microcontrollers.
- Real-Time Clock/Calendar with full timekeeping (seconds, minutes, hours, day, date, month, year; leap-year aware).
- External 32.768 kHz crystal input for accurate timekeeping.
- Battery-backup operation (VBAT) to retain time and non-volatile RAM during power-down.
- Trickle-charge circuit to maintain backup supply from VCC (when enabled).
- 56 bytes of non-volatile RAM (NV RAM) for user data storage that persists without power.
- SQW/interrupt output for square-wave signaling or alarm/interrupt events.
Optional/notes:
- Fully I2C-addressable registers; suitable for embedded timekeeping and simple data storage needs.
- Small 8-pin package (MCP7940NT) with typical use in low-power applications.

- Pin count: 8 pins (MCP7940NT-E/SN in an 8‑pin package).
- Primary function: I2C real‑time clock with 32.768 kHz oscillator, battery backup, and square‑wave output. It provides timekeeping registers (with battery-backed RAM) accessible via I2C. Pin functions (typical 8‑pin layout): VDD, VSS, VBAT, SDA, SCL, OSC1, OSC2, SQW/OUT.

- Manufacturer: Microchip Technology Inc.
- What kind of company: A global American semiconductor company that designs, manufactures, and markets microcontrollers, analog and memory products for embedded systems (publicly traded, ticker MCHP).

Application areas of MCP7940NT-E/SN:
- Real-time clock/calendar for microcontrollers via I2C
- Time stamping and scheduling in data loggers, meters, sensors, and consumer electronics
- Alarm and wake-up timer to wake CPUs in low-power designs
- Battery-backed non-volatile RAM for configuration data and event logging
- Power-fail detection with seamless back-up clock for uninterrupted timekeeping
- Time-based control and scheduling in home automation, wearables, and telecom equipment

An 8-pin SOIC (Plastic Small‑Outline) package.