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MCP7940N

MCHPMCP7940N

Microchip Technology
Real Time Clock I2C GP RTCC 64B SRAM
5,458 in stock
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Overview

The MCP7940N is a low-power Real-Time Clock and Calendar (RTCC) from Microchip Technology that utilizes an I2C interface. It features digital timing compensation for crystal calibration, battery backup support to maintain time during power loss, and a dedicated 64-byte SRAM for user data storage. The device is designed to provide accurate timekeeping with minimal power consumption, operating down to 1.8V.

Why Choose This Part

The MCP7940N stands out due to its digital trimming circuit, which allows for software-based calibration of the 32.768 kHz crystal to improve accuracy. It includes a sophisticated power-sense circuit that automatically switches to the backup supply and records the timestamp of the power transition. Additionally, its high ESD protection of over 4,000V makes it robust for industrial environments.

Applications

Power-Fail Logging
Utilizes the built-in power-fail time-stamp feature to record the exact duration and time of power loss events.
Battery-Powered Instrumentation
Ideal for handheld devices where low current consumption (down to 1.2uA typical at 3V for timekeeping) is critical for battery life.
Embedded System Scheduling
Provides precise alarm and calendar functions to wake up a host MCU or trigger periodic system tasks.
Data Loggers
The 64-byte SRAM allows for storing critical configuration or state data that must persist alongside the timestamp.

Getting Started

To evaluate the MCP7940N, you can use the MCP79410 RTCC PICtail Plus Daughter Board or connect a standard SOIC-8 breakout to any I2C-enabled microcontroller. Implementation requires an external 32.768 kHz tuning fork crystal and a backup battery (such as a CR2032) connected to the Vbat pin. Developers should use the I2C bus at speeds up to 400 kHz and consult Microchip Application Note AN2340 for detailed calibration procedures.

MCP7940 Family

Comparing specs that differ across variants. The current part is highlighted.

Part Number Features Package Temp Range Current - Timekeeping (Max) Stock
MCP7940N (this part) — — — — 5,458
MCP7940NT-I/MS Alarm, Leap Year, .. TSSOP-8 -40degC ~ 85degC 1.2uA 22,374
MCP7940NT-I/SN Alarm, Leap Year, .. SOIC-8 -40degC ~ 85degC 1.2uA 32,168
MCP7940M-I/SN Alarm, Leap Year, .. SOIC-8 -40degC ~ 85degC 1uA 1,594
MCP7940N-I/MS Alarm, Leap Year, .. TSSOP-8 -40degC ~ 85degC 1.2uA 1,310
MCP7940M-I/MS Alarm, Leap Year, .. TSSOP-8 -40degC ~ 85degC 1uA 1,604
MCP7940N-I/ST Alarm, Leap Year, .. TSSOP-8 -40degC ~ 85degC 1.2uA 729
MCP7940MT-I/MNY Alarm, Leap Year, .. WFDFN-8 -40degC ~ 85degC 1uA 10,857
MCP7940MT-I/SN Alarm, Leap Year, .. SOIC-8 -40degC ~ 85degC 1uA 2,696
MCP7940NT-E/MS Alarm, Leap Year, .. TSSOP-8 -40degC ~ 125degC 1.2uA 7,080
MCP79400T-I/SN Alarm, Leap Year, .. SOIC-8 -40degC ~ 85degC 1.2uA 3,428
MCP7940N-I/P Alarm, Leap Year, .. DIP-8 -40degC ~ 85degC 1.2uA 1,254
MCP7940N-I/SN Alarm, Leap Year, .. SOIC-8 -40degC ~ 85degC 1.2uA 8,482