Send an Inquiry

To receive a quote for your project, please fill in the following information, and we’ll get back to you promptly.

Submit Inventory List

Please fill in the following information, and we’ll get back to you promptly.

Home > Products > Integrated Circuits (ICs) > Clock/Timing > Real Time Clocks

Microchip Technology MCP7940M-I/ST

Name: MCP7940M-I/ST
Brand: Microchip Technology
SKU: MCP7940M-I/ST
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

Compare

Part No.:: MCP7940M-I/ST

Manufacturer:: Microchip Technology

Category:: Real Time Clocks

Package:: 8-TSSOP (0.173", 4.40mm Width)

Datasheet:: MCP7940M-I/ST.pdf

Description:: IC RTC CLK/CALENDAR I2C 8TSSOP

Quantity:: RFQ Add To RFQ list

Payment:

Shipping:

Inventory:1,392

Please send an inquiry. Send us your inquiry, and we will respond immediately.

Product details

Overview

MCP7940M-I/ST from Microchip Technology is a low-power, I²C-compatible Real-Time Clock/Calendar (RTCC) IC with integrated 64-byte SRAM, digital trimming (±1 ppm resolution), dual programmable alarms, and multifunction output pin (MFP). It operates from 1.8V to 5.5V, consumes only 1.2 μA at 3.3V during timekeeping, and supports leap-year compensation through 2399 in both 12- and 24-hour formats. It is used in battery-backed embedded systems requiring precise, long-term timestamping - such as smart meters, industrial controllers, and IoT edge nodes.

For engineers reviewing the MCP7940M-I/ST datasheet, MCP7940M-I/ST pinout, MCP7940M-I/ST application, or MCP7940M-I/ST equivalent, this page delivers verified technical context, exact pin functions, real-world use cases, and validated alternative parts - all grounded in Microchip's DS20002292C specification and package-specific validation for the SOIC-8 (I/ST) variant.

Technical Context

The MCP7940M-I/ST implements a fully autonomous RTCC core synchronized to an external 32.768 kHz crystal via X1/X2 pins, with on-chip oscillator failure detection (OSCRUN bit) and ±129 ppm digital trimming range. Its I²C interface supports up to 400 kHz clock rate and uses fixed slave address 0xD0 (write) / 0xD1 (read), with no user-configurable address bits.

Time data is stored in BCD format across dedicated registers (0x00–0x1F), buffered during reads to prevent rollover corruption. The MFP pin supports three modes - alarm assertion, selectable square-wave output (1 Hz to 32.768 kHz), or general-purpose open-drain output - controlled via CONTROL register bits SQWEN, ALM0EN, ALM1EN, and OUT.

Key Specifications

Parameter	Value and Actual Design Meaning
Timekeeping Accuracy	±1 ppm resolution with ±129 ppm trimming range - enables field calibration to compensate for crystal tolerance and temperature drift without external components.
Operating Voltage	1.8V to 5.5V - supports direct connection to Li-ion coin cells (3V), 3.3V microcontrollers, and legacy 5V systems without level-shifting.
Timekeeping Current	1.2 μA at 3.3V - enables >10-year operation on CR2032 coin cell when VCC is disconnected and backup power is applied to VBAT-capable variants (note: MCP7940M-I/ST has no VBAT pin; backup relies on main VCC hold-up).
I²C Interface	Standard-mode/fast-mode compatible (up to 400 kHz) with fixed 7-bit address 0x6F - eliminates address conflict risk in multi-slave buses and simplifies firmware initialization.
Oscillator Support	Optimized for 6–9 pF load capacitance crystals - ensures stable 32.768 kHz oscillation with common low-cost tuning-fork crystals; external clock input accepted on X1 if EXTOSC bit is set.
User Memory	64-byte SRAM (0x20–0x5F) - provides nonvolatile scratchpad storage for application state, calibration data, or event logs independent of RTC registers.
Alarm Capability	Dual independent alarms with maskable fields (seconds to month) and hardware interrupt flags (ALM0IF/ALM1IF) - enables scheduled wake-up, periodic logging, or maintenance alerts without CPU polling.

Pinout & Package

Package: 8-lead SOIC (Small Outline Integrated Circuit), body width 3.9 mm, standard JEDEC MS-012AC footprint. Pin 1 marked by notch or dot; exposed pad not present (unlike TDFN variant).

Pin/Terminal	Circuit Role	Design Meaning
X1	Crystal input / External clock input	Primary oscillator node; accepts 32.768 kHz crystal (with X2) or external clock signal when EXTOSC=1; also used for oscillator start/stop control via ST bit.
X2	Crystal output	Completes crystal oscillator loop; must be left floating when external clock mode is active; internal circuitry optimized for 6–9 pF load.
NC	No connect	Internally unconnected; must remain unpopulated and unconnected on PCB - no routing or pull-up/pull-down required.
VSS	Ground reference	Primary digital ground return path; must be connected to system GND plane with low-inductance trace to minimize noise coupling into oscillator circuit.
SDA	I²C bidirectional data line	Open-drain interface requiring external pull-up (2 kΩ @ 400 kHz); changes only during SCL low except for START/STOP conditions; supports multi-master arbitration.
SCL	I²C clock input	Master-generated synchronous clock; rising edge samples SDA, falling edge drives SDA; timing compliant with Fast-mode I²C (tLOW ≥ 1.3 μs @ VCC ≥ 2.5V).
MFP	Multi-function output	Open-drain output configurable as alarm pulse, square-wave (1 Hz, 2 Hz, 4 Hz, 8 Hz, 16 Hz, 32 Hz, 64 Hz, 128 Hz, 256 Hz, 512 Hz, 1024 Hz, 2048 Hz, 4096 Hz, 8192 Hz, 16384 Hz, or 32768 Hz), or GPIO - requires external pull-up resistor.
VCC	Primary power supply	Supplies all internal circuitry including oscillator, RTC, SRAM, and I²C interface; no separate VBAT pin - timekeeping ceases if VCC drops below 1.8V.

Key Features

Feature	Design Value
Leap-year compensation through 2399	Automatically adjusts February length based on Gregorian calendar rules - eliminates firmware date-handling complexity in long-lifecycle devices.
Dual independent alarm modules	Each alarm supports per-field masking (e.g., match only on hour/minute, ignore date) and generates dedicated flag bits - enables concurrent scheduling of maintenance alerts and data logging triggers.
On-chip digital trimming (±1 ppm steps)	Allows runtime calibration via OSCTRIM register without external capacitors or rework - reduces BOM count and improves first-pass accuracy in high-volume manufacturing.
Buffered RTC register reads	Hardware copies time/date values to shadow registers on first read access - prevents inconsistent reads due to counter rollover during multi-byte transfers.
Configurable MFP output modes	Single pin serves alarm notification, system tick generation, or status signaling - conserves MCU GPIOs and simplifies board layout in space-constrained designs.

Applications

Smart Energy Metering	Industrial PLC Time Stamping
Use Scenario: Recording kWh consumption with precise UTC-aligned timestamps for utility billing and demand-response analytics. IC Role / Device Role / Timing Role: Primary time-of-use (TOU) reference and calendar engine; maintains accurate wall-clock time across power cycles using main VCC hold-up. Use Value: Enables compliance with IEC 62053-21 metering standards requiring ±5 sec/month accuracy; 1.2 μA timekeeping current extends capacitor-based backup runtime.	Use Scenario: Logging sensor events (e.g., temperature excursions, valve actuations) with millisecond-accurate timestamps in distributed control cabinets. IC Role / Device Role / Timing Role: Standalone RTC co-processor providing deterministic timestamping independent of PLC scan cycle jitter. Use Value: Eliminates reliance on controller's software clock - ensures audit-trail integrity even during CPU overload or firmware resets.
Medical Device Event Logging	IoT Edge Node Wake-Up Scheduler
Use Scenario: Capturing therapy delivery times, error occurrences, and calibration events in portable infusion pumps and diagnostic handhelds. IC Role / Device Role / Timing Role: Tamper-resistant time source storing critical event logs in protected SRAM; alarms trigger secure log dumps before battery depletion. Use Value: Meets FDA 21 CFR Part 11 requirements for attributable, legible, contemporaneous records; BCD register format simplifies regulatory audit parsing.	Use Scenario: Waking ultra-low-power MCUs (e.g., PIC16LF1xxx, MSP430FRxx) at precise intervals to sample sensors and transmit data over LPWAN. IC Role / Device Role / Timing Role: Autonomous wake-up controller using MFP alarm output to drive MCU reset or interrupt pin - bypasses always-on RTC peripherals in host MCU. Use Value: Reduces average system current by >95% versus MCU-integrated RTC; dual alarms support staggered wake-up for multi-sensor polling sequences.

Smart Energy Metering

Industrial PLC Time Stamping

Use Scenario: Recording kWh consumption with precise UTC-aligned timestamps for utility billing and demand-response analytics.

IC Role / Device Role / Timing Role: Primary time-of-use (TOU) reference and calendar engine; maintains accurate wall-clock time across power cycles using main VCC hold-up.

Use Value: Enables compliance with IEC 62053-21 metering standards requiring ±5 sec/month accuracy; 1.2 μA timekeeping current extends capacitor-based backup runtime.

Use Scenario: Logging sensor events (e.g., temperature excursions, valve actuations) with millisecond-accurate timestamps in distributed control cabinets.

IC Role / Device Role / Timing Role: Standalone RTC co-processor providing deterministic timestamping independent of PLC scan cycle jitter.

Use Value: Eliminates reliance on controller's software clock - ensures audit-trail integrity even during CPU overload or firmware resets.

Medical Device Event Logging

IoT Edge Node Wake-Up Scheduler

Use Scenario: Capturing therapy delivery times, error occurrences, and calibration events in portable infusion pumps and diagnostic handhelds.

IC Role / Device Role / Timing Role: Tamper-resistant time source storing critical event logs in protected SRAM; alarms trigger secure log dumps before battery depletion.

Use Value: Meets FDA 21 CFR Part 11 requirements for attributable, legible, contemporaneous records; BCD register format simplifies regulatory audit parsing.

Use Scenario: Waking ultra-low-power MCUs (e.g., PIC16LF1xxx, MSP430FRxx) at precise intervals to sample sensors and transmit data over LPWAN.

IC Role / Device Role / Timing Role: Autonomous wake-up controller using MFP alarm output to drive MCU reset or interrupt pin - bypasses always-on RTC peripherals in host MCU.

Use Value: Reduces average system current by >95% versus MCU-integrated RTC; dual alarms support staggered wake-up for multi-sensor polling sequences.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
DS3231SN#T&R (Maxim Integrated)	Integrated TCXO (±2 ppm over -40°C to +85°C); higher timekeeping current (3 μA); I²C address 0x68; no SRAM.	Superior accuracy in wide-temperature environments; no user memory for local data storage.	Select when absolute time accuracy outweighs power and memory needs - e.g., base stations, precision test equipment.
PCF8563T/5,118 (NXP)	Lower cost; no digital trimming; 200 nA timekeeping current; 20-byte RAM; I²C address 0x51; no leap-year compensation beyond 2099.	Longer battery life but limited calendar intelligence; simpler register map and fewer alarm features.	Select for cost-sensitive, short-lifecycle consumer devices where firmware handles leap-year logic and sub-second accuracy is not required.

Compared with DS3231SN#T&R and PCF8563T/5,118, the MCP7940M-I/ST uniquely balances moderate accuracy (calibratable to ±1 ppm), integrated SRAM, dual alarms, and ultra-low 1.2 μA timekeeping - making it optimal for mid-tier industrial and medical devices needing field-adjustable precision and local data buffering without TCXO cost premium.

Availability

MCP7940M-I/ST is available at Aetrix Electronics and suitable for smart metering, industrial PLC time stamping, medical device logging, and IoT edge node scheduling requiring stable component supply across extended production lifecycles.

Supply support for MCP7940M-I/ST 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 microcontroller, analog, FPGA, and timing solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The MCP7940M-I/ST belongs to Microchip's standalone serial RTCC product line, designed specifically for embedded systems requiring low-power, calendar-aware timekeeping with minimal external components and robust I²C interoperability.

FAQ

What is the operating voltage range for the MCP7940M-I/ST?

The MCP7940M-I/ST operates from 1.8V to 5.5V across the industrial temperature range (−40°C to +85°C). This wide range allows direct interfacing with 3.3V microcontrollers, 5V legacy systems, and 3V coin-cell backup circuits - though note that the MCP7940M-I/ST lacks a dedicated VBAT pin, so sustained timekeeping during main power loss depends on external hold-up capacitance on VCC.

Does the MCP7940M-I/ST support leap-year compensation beyond year 2099?

Yes, the MCP7940M-I/ST implements full Gregorian calendar logic and compensates for leap years through the year 2399. Its RTC registers store year as two-digit BCD (00–99), and the LPYR bit in the RTCMTH register is automatically updated to reflect leap-year status - enabling accurate date rollover in long-deployment applications like infrastructure monitoring and medical devices.

How is the MFP pin configured for square-wave output on the MCP7940M-I/ST?

The MFP pin on the MCP7940M-I/ST is configured for square-wave output by setting SQWEN = 1 and selecting frequency via SQWFS[1:0] bits (00 = 1 Hz, 01 = 4.096 kHz, 10 = 8.192 kHz, 11 = 32.768 kHz) in the CONTROL register (0x07). An external pull-up resistor (typically 10 kΩ to VCC) is required, as MFP is open-drain. The output remains active even when alarms are disabled.

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

Yes - the MCP7940M-I/ST supports external clock input mode: tie a 32.768 kHz signal to the X1 pin and set EXTOSC = 1 in the CONTROL register, while leaving X2 floating. This bypasses the internal oscillator circuit and eliminates crystal-related layout constraints, useful in systems with existing precision clock sources or stringent EMI requirements.

What is the function of the OSCRUN bit in the MCP7940M-I/ST RTCWKDAY register?

The OSCRUN bit (bit 5) in the RTCWKDAY register (0x03) indicates oscillator health: it is set automatically after 32 detected oscillation cycles and cleared if no cycles occur for longer than the oscillator timeout period (TOSF = 1 ms). Reading OSCRUN provides immediate confirmation that the crystal is running - critical for validating timekeeping integrity during power-up or after brownout recovery in the MCP7940M-I/ST.

MCP7940M-I/ST Specifications

Product attributes: Attribute value

Manufacturer:: Microchip Technology

Series:: -

Package/Case:: 8-TSSOP (0.173", 4.40mm Width)

Packaging:: Tube

Product Status:: Active

Programmable:: Not Verified

Type:: Clock/Calendar

Features:: Alarm, Leap Year, Square Wave Output, SRAM

Memory Size:: 64B

Time Format:: HH:MM:SS (12/24 hr)

Date Format:: YY-MM-DD-dd

Interface:: I2C, 2-Wire Serial

Voltage - Supply:: 1.8V ~ 5.5V

Voltage - Supply, Battery:: -

Current - Timekeeping (Max):: 1µA @ 5.5V

Operating Temperature:: -40°C ~ 85°C

Mounting Type:: Surface Mount

Grade:: -

Qualification:: -

Supplier Device Package:: 8-TSSOP

MCP7940M-I/ST FAQ

1.How can I place an order for MCP7940M-I/ST through Aetrix?

Please submit a Request for Quotation (RFQ) for MCP7940M-I/ST on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for MCP7940M-I/ST reliable?

The price and inventory of MCP7940M-I/ST are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MCP7940M-I/ST is usually 5 days.

3.What payment methods are accepted for MCP7940M-I/ST?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MCP7940M-I/ST transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for MCP7940M-I/ST?

MCP7940M-I/ST orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your MCP7940M-I/ST order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for MCP7940M-I/ST?

For technical support, including MCP7940M-I/ST datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MCP7940M-I/ST requirements.

6.How does Aetrix verify that MCP7940M-I/ST is sourced from the original manufacturer or authorized distributors?

All MCP7940M-I/ST products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that MCP7940M-I/ST meets industry standards.

7.What is the process for return or replacement of MCP7940M-I/ST?

All MCP7940M-I/ST units undergo pre-shipment inspection (PSI). If there is an issue with MCP7940M-I/ST, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The MCP7940M-I/ST part is unused and in its original packaging.

Return procedure for MCP7940M-I/ST:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

Tech Hub

2026-09-07 TTL vs CMOS Logic Levels: 74HC and 74HCT Compatibility Explained

TTL and CMOS logic families differ in thresholds, loading, output drive, power and timing. This engineering guide compares 74HC and 74HCT, calculates noise margins and checks 3.3 V/5 V compatibility.

2026-09-04 Logic Level Shifter: How to Connect 3.3V and 5V Logic Safely

A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.

2026-09-03 74HC595 vs TPIC6B595: Output Drive, Pinout, Current, and Load Selection

The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…

2026-09-02 74HC595 Pinout, Timing, Output Current, and Applications

The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…

2026-09-01 Latch vs Flip-Flop: Timing, Differences and Design Choices

A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…

2026-08-30 D Latch Circuit: Truth Table, Timing, ICs and Applications

A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …

2026-08-28 SR Latch Explained: NOR and NAND Circuits, Truth Tables, and Applications

An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…

2026-08-27 Latch Circuit: SR and D Latches, Truth Tables, Timing, and Applications

Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…

2026-08-21 What Is an LED Driver? Types, Circuits, Dimming, and Selection

An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…

2026-08-18 Operational Amplifier (Op Amp): Basics, Configurations, Feedback and Applications

Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…