Microchip Technology MCP7940M-I/MS

Overview

MCP7940M-I/MS from Microchip Technology is a low-power, I²C-compatible Real-Time Clock/Calendar (RTCC) IC with integrated 64-byte SRAM, digital trimming, dual programmable alarms, and multifunction output pin. It maintains time across seconds, minutes, hours, day of week, date, month, and year with leap-year compensation to 2399, operates from 1.8V–5.5V, and draws only 1.2 μA at 3.3V for timekeeping - used in battery-backed embedded systems requiring precise, long-term timestamping.

For engineers reviewing the MCP7940M-I/MS datasheet, MCP7940M-I/MS pinout, MCP7940M-I/MS application, or MCP7940M-I/MS equivalent, this page delivers verified technical context, exact pin functions, real-world timing use cases, and validated alternative parts - all grounded in Microchip's DS20002292C specification and package-specific MSOP-8 implementation.

Technical Context

The MCP7940M-I/MS implements a fully autonomous RTCC using an internal oscillator circuit optimized for 32.768 kHz crystals with 6–9 pF load capacitance. Its on-chip digital trimming provides ±1 ppm resolution over a ±129 ppm range, enabling precise frequency calibration without external components.

It supports I²C up to 400 kHz, features two independent alarm modules with maskable fields (down to seconds), and uses BCD-encoded registers (0x00–0x1F) with automatic rollover handling and buffered reads to prevent counter corruption during access - all managed via a fixed slave address prefix '1101111x'.

Key Specifications

Pinout & Package

Package: 8-pin MSOP (MCP7940M-I/MS), body size 3.0 mm × 3.0 mm, exposed pad optional to VSS.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar real-time clock/calendar applications.

Compared with MCP7940N-I/MS, the MCP7940M-I/MS integrates a calibrated crystal oscillator - reducing component count and layout risk. Against DS3231M+, it trades absolute accuracy for on-chip SRAM, dual alarms, and software-configurable trimming - making it optimal for cost-sensitive, feature-rich embedded timing.

Availability

MCP7940M-I/MS is available at Aetrix Electronics and suitable for smart energy metering, industrial HMI logging, medical wearable monitoring, and automotive infotainment requiring stable component supply across extended production lifecycles.

Supply support for MCP7940M-I/MS includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Microchip Technology Inc. is a leading provider of microcontrollers, analog devices, and timing solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The MCP7940M belongs to Microchip's standalone RTCC product line, designed specifically for embedded systems needing low-power, high-reliability timekeeping with integrated memory and flexible alarm functionality - not dependent on host processor resources.

FAQ

What is the primary function of the MCP7940M-I/MS in a system?

The MCP7940M-I/MS serves as a self-contained Real-Time Clock/Calendar IC that maintains accurate time and date information - including seconds, minutes, hours, day of week, date, month, and year - with leap-year compensation through 2399. It operates independently of the host microcontroller, retains time during power loss via backup supply, and provides timestamping, alarm triggering, and 64-byte SRAM storage. The MCP7940M-I/MS is engineered for minimal power consumption (1.2 μA at 3.3V) and robustness in industrial environments.

How does the MCP7940M-I/MS handle oscillator calibration?

The MCP7940M-I/MS implements on-chip digital trimming with ±1 ppm resolution over a ±129 ppm range, controlled via the OSCTRIM register (0x08). This allows fine-tuning of the 32.768 kHz oscillator frequency to compensate for crystal tolerance and temperature-induced drift - eliminating the need for external variable capacitors. Calibration is performed in firmware by writing to TRIMVAL[6:0] and SIGN bits, and the setting persists across power cycles. The MCP7940M-I/MS does not require external calibration hardware.

Can the MCP7940M-I/MS operate without an external crystal?

Yes - the MCP7940M-I/MS supports external clock input mode: when the EXTOSC bit (CONTROL[4]) is set, the X1 pin accepts a 32.768 kHz square-wave clock signal, and X2 is left floating. This bypasses the internal crystal oscillator circuit entirely. However, the device still requires valid time/date initialization and I²C communication; the core RTCC, SRAM, and alarm functions remain fully operational. The MCP7940M-I/MS does not support higher-frequency or non-32.768 kHz clock inputs.

What is the role of the MFP pin on the MCP7940M-I/MS?

The MFP (Multifunction Pin) on the MCP7940M-I/MS is an open-drain output configurable via CONTROL register bits (SQWEN, ALMxEN, OUT) to serve three roles: (1) alarm pulse output (active-low on match), (2) selectable square-wave clock (32.768 kHz, 1024 Hz, 32 Hz, or 1 Hz), or (3) general-purpose output driven by the OUT bit. It requires an external pull-up resistor (typically 10 kΩ to VCC). The MCP7940M-I/MS does not support input or bidirectional use of MFP - it is output-only.

Does the MCP7940M-I/MS support battery backup switching?

The MCP7940M-I/MS does not include built-in battery switchover circuitry. It relies on external design: VCC must be connected to a backup power source (e.g., coin cell) through a diode or ideal diode controller to maintain operation during main supply loss. The device draws only 1.2 μA in timekeeping mode at 3.3V, enabling multi-year backup operation. All registers and SRAM retain state as long as VCC remains ≥1.8V - the MCP7940M-I/MS has no dedicated VBAT pin or internal power-path management.