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Microchip Technology MCP7940MT-I/MS
- Part No.:
- MCP7940MT-I/MS
- Manufacturer:
- Microchip Technology
- Category:
- Real Time Clocks
- Package:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Datasheet:
-
MCP7940MT-I/MS.pdf
- Description:
- IC RTC CLK/CALENDAR I2C 8MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:8,760
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Product details
Overview
MCP7940MT-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 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 to 5.5V, and draws only 1.2 μA typical timekeeping current at 3.3V. It is used in battery-backed embedded systems requiring precise, long-term timekeeping - such as smart meters, industrial controllers, and IoT edge nodes.
For engineers reviewing the MCP7940MT-I/MS datasheet, MCP7940MT-I/MS pinout, MCP7940MT-I/MS application, or MCP7940MT-I/MS equivalent, key selection criteria include its ±1 ppm digital trimming resolution, 32.768 kHz crystal oscillator optimized for 6–9 pF load capacitance, I²C interface up to 400 kHz, open-drain MFP configurable as alarm output or square-wave generator, and industrial temperature range (−40°C to +85°C).
Technical Context
The MCP7940MT-I/MS implements a fully autonomous RTCC using an on-chip oscillator circuit designed for external 32.768 kHz tuning-fork crystals. Its timekeeping engine uses binary-coded decimal (BCD) registers with automatic rollover handling for variable-length months and leap years (2001–2399), and supports both 12- and 24-hour formats with user-defined weekday mapping.
It features two independent alarm modules (ALM0 and ALM1), each configurable to trigger on match conditions down to the second or periodically (minute/hour/day/weekday/month). The multifunction pin (MFP) serves as open-drain output for alarm assertion, selectable-frequency square wave (32.768 kHz, 1024 Hz, 32 Hz, or 1 Hz), or general-purpose output - all controlled via the CONTROL register.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Timekeeping Accuracy | ±1 ppm digital trimming resolution over ±129 ppm range enables fine frequency calibration to compensate crystal tolerance and temperature drift. |
| Operating Voltage | 1.8V to 5.5V supply range supports direct integration into mixed-voltage systems (e.g., 3.3V microcontrollers or 5V legacy interfaces) without level-shifting. |
| Timekeeping Current | 1.2 μA typical at 3.3V enables multi-year operation on coin-cell batteries (e.g., CR2032) in always-on timekeeping applications. |
| I²C Interface Speed | Up to 400 kHz clock rate allows fast configuration and readback of time/date registers and 64-byte SRAM without blocking system bus performance. |
| Crystal Load Capacitance | Optimized for 6–9 pF external crystals; internal oscillator design avoids need for fixed on-die capacitors, enabling flexibility in crystal selection and layout. |
| Alarm Capability | Dual independent alarms with maskable fields (second through month) support complex scheduling - e.g., daily wake-up at 6:00 AM or monthly data sync on the 1st. |
| SRAM Capacity | 64 bytes of battery-backed user-accessible SRAM (addresses 0x20–0x5F) provide nonvolatile storage for calibration data, event logs, or configuration state. |
Pinout & Package
Package: 8-pin MSOP (MCP7940MT-I/MS), lead-free, RoHS-compliant, 3.0 mm × 3.0 mm body, 0.65 mm pitch.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| X1 | Crystal Input / External Clock Input | Primary oscillator input for 32.768 kHz crystal; also accepts external clock signal when EXTOSC bit is set - enables flexible timing source selection. |
| X2 | Crystal Output | Crystal oscillator output node; must be left floating when external clock mode is active - critical for stable oscillation in crystal mode. |
| NC | No Connect | Internally unconnected; must remain unpopulated and unconnected on PCB - no routing or pull-up/pull-down required. |
| VSS | Ground Reference | Primary ground return for all internal circuits and I²C bus; requires low-impedance connection to system ground plane to minimize noise coupling into oscillator. |
| SDA | I²C Bidirectional Data | Open-drain serial data line requiring external pull-up resistor (2 kΩ typical for 400 kHz); changes only during SCL low to avoid spurious Start/Stop conditions. |
| SCL | I²C Clock Input | Master-generated clock synchronizing all I²C transfers; rising edge samples SDA, falling edge drives SDA - defines timing compliance per I²C Fast Mode spec. |
| MFP | Multifunction Output | Open-drain output configurable as alarm flag, programmable square-wave (1 Hz to 32.768 kHz), or GPIO - requires external pull-up and supports interrupt-driven system wake-up. |
| VCC | Power Supply | Primary power input (1.8–5.5V); supplies all internal logic, oscillator, and SRAM; decoupling capacitor (0.1 μF ceramic) required within 5 mm of pin. |
Key Features
| Feature | Design Value |
|---|---|
| On-chip digital trimming | ±1 ppm resolution over ±129 ppm range allows field calibration without hardware changes - eliminates need for external trimmer capacitors or crystal swaps. |
| Dual programmable alarms | Independent ALM0 and ALM1 with maskable fields (down to seconds) enable precise event scheduling - e.g., one alarm for daily maintenance, another for battery-low warning. |
| Versatile MFP output | Configurable via CONTROL register as alarm pulse, square-wave generator (four frequencies), or general-purpose output - reduces BOM count by replacing discrete timer or GPIO expanders. |
| 64-byte SRAM block | User-accessible memory space (0x20–0x5F) retains data during VCC brownout when backed by external capacitor or battery - stores firmware state, sensor offsets, or usage counters. |
| Leap-year compensation | Automatic correction from 2001 to 2399 ensures calendar accuracy across decades without host MCU intervention - critical for unattended remote deployments. |
| Oscillator failure detection | OSCRUN bit in RTCWKDAY register reports real-time oscillator status - enables fail-safe logging or fallback to backup time source if crystal stops. |
Applications
| Smart Energy Metering | Industrial PLC HMI |
|---|---|
|
Use Scenario: Battery-powered electricity meter logging consumption every 15 minutes and timestamping events for utility billing cycles. IC Role / Device Role / Timing Role: Primary timekeeping engine maintaining accurate UTC-aligned timestamps independent of main processor sleep states. Use Value: 1.2 μA timekeeping current extends coin-cell life beyond 10 years; ±1 ppm trimming ensures billing-grade time accuracy over temperature and aging. |
Use Scenario: Human-machine interface panel in factory automation that displays real-time machine uptime, shift schedules, and maintenance alerts. IC Role / Device Role / Timing Role: Standalone RTCC providing wall-clock time and triggering daily log rotation and shift-change notifications via MFP alarm output. Use Value: Dual alarms allow concurrent scheduling - e.g., ALM0 triggers midnight log archive, ALM1 triggers 6:00 AM shift-start alert - without MCU polling overhead. |
| Medical Wearable Tracker | Networked Building Controller |
|
Use Scenario: Portable ECG monitor recording heart-rate trends with timestamps for clinician review, operating on rechargeable Li-ion with periodic deep-sleep. IC Role / Device Role / Timing Role: Low-power timekeeper preserving calendar continuity during MCU deep-sleep; wakes system via MFP alarm for scheduled measurements. Use Value: 1.8V–5.5V operation matches wearable battery discharge curve; 64-byte SRAM stores last 16 measurement timestamps locally before upload. |
Use Scenario: HVAC controller managing zone schedules, occupancy-based heating/cooling, and energy reporting across commercial buildings. IC Role / Device Role / Timing Role: Central time reference synchronizing multiple sub-controllers and generating time-triggered commands (e.g., "pre-heat at 5:30 AM"). Use Value: Leap-year compensation ensures seasonal schedules (e.g., daylight savings transitions) execute correctly for decades without firmware updates. |
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 |
|---|---|---|---|
| DS3231M+ | Integrated TCXO provides ±2 ppm accuracy over −40°C to +85°C; higher precision but no SRAM; consumes 3.5 μA typical timekeeping current. | Better suited for GPS-disciplined or high-accuracy instrumentation where temperature-induced drift must be minimized; lacks user SRAM. | Select DS3231M+ when absolute time accuracy > ±2 ppm is required and SRAM is unnecessary; MCP7940MT-I/MS preferred when local data storage or lower quiescent current is critical. |
| PCF8563T | Lower-cost I²C RTC with 236-byte RAM; no digital trimming; 3 μA timekeeping current; limited alarm capability (only hour/minute match). | Targeted at cost-sensitive consumer electronics with basic timekeeping needs; lacks leap-year compensation beyond 2099 and fine-grained alarm masking. | Choose PCF8563T for budget-constrained designs where ±20 ppm accuracy suffices and advanced alarms/SRAM are not needed; MCP7940MT-I/MS delivers superior flexibility and longevity. |
Compared with DS3231M+ and PCF8563T, the MCP7940MT-I/MS uniquely balances ultra-low power (1.2 μA), on-the-fly digital trimming (±1 ppm), dual maskable alarms, and integrated SRAM - making it optimal for battery-critical, long-lifecycle industrial and medical devices requiring both precision and local data retention.
Availability
MCP7940MT-I/MS is available at Aetrix Electronics and suitable for smart metering, industrial HMI, medical wearables, and building automation systems requiring stable component supply, long-term lifecycle support, and guaranteed traceability.
Supply support for MCP7940MT-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 microcontroller, analog, FPGA, and timing solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.
The MCP7940M family was designed specifically for embedded systems requiring highly reliable, low-power, feature-rich real-time clock functionality - emphasizing long battery life, field-calibratable accuracy, and seamless I²C integration without external support components.
FAQ
What is the primary function of the MCP7940MT-I/MS?
The MCP7940MT-I/MS is a standalone Real-Time Clock/Calendar (RTCC) IC that maintains accurate time and date information - including seconds, minutes, hours, day of week, date, month, and year - with leap-year compensation to 2399. It operates autonomously using an external 32.768 kHz crystal and communicates via I²C. The MCP7940MT-I/MS also integrates 64-byte SRAM and dual programmable alarms, making it ideal for battery-powered embedded applications requiring long-term timekeeping integrity.
How does the digital trimming feature work in the MCP7940MT-I/MS?
The MCP7940MT-I/MS implements on-chip digital trimming via the OSCTRIM register (address 0x08), offering ±1 ppm resolution across a ±129 ppm adjustment range. This allows precise compensation for crystal frequency deviations caused by manufacturing tolerance, aging, or temperature effects. Trimming is applied directly to the oscillator circuit without external components, and the setting persists across power cycles when stored in the device's nonvolatile control bits - ensuring consistent accuracy without recalibration after reboot.
Can the MCP7940MT-I/MS operate without an external crystal?
Yes - the MCP7940MT-I/MS supports external clock input mode. When the EXTOSC bit in the CONTROL register is set, the device disables its internal crystal oscillator and accepts a 32.768 kHz square-wave clock signal applied to the X1 pin; X2 is left floating. This mode is useful when system-level clock distribution is preferred over discrete crystals, or when board space constraints prohibit crystal placement near the IC. All timekeeping, alarm, and SRAM functions remain fully operational in this configuration.
What is the role of the MFP pin on the MCP7940MT-I/MS?
The MFP (Multifunction Pin) on the MCP7940MT-I/MS is an open-drain output configurable via the CONTROL register. It can serve as an alarm flag (asserted when ALM0IF or ALM1IF is set), a square-wave generator (at 32.768 kHz, 1024 Hz, 32 Hz, or 1 Hz), or a general-purpose output. Because it is open-drain, it requires an external pull-up resistor to VCC. In alarm mode, it enables interrupt-driven wake-up of a sleeping host MCU; in square-wave mode, it eliminates need for external clock buffers in timing-sensitive subsystems.
Does the MCP7940MT-I/MS support battery backup for timekeeping during main power loss?
The MCP7940MT-I/MS does not include an internal battery switchover circuit, but it supports external battery backup via VCC pin. When main VCC drops below operating voltage, a backup power source (e.g., coin cell or supercapacitor) connected through a diode or ideal diode controller can maintain VCC above 1.8V, allowing continuous timekeeping and SRAM retention. The device draws only 1 μA in data-retention mode (oscillator off) and 1.2 μA during active timekeeping - enabling multi-year operation on standard backup sources. Proper decoupling and low-leakage backup path design are essential for reliability.
MCP7940MT-I/MS Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Packaging:
- Tape & Reel (TR)
- 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-MSOP
MCP7940MT-I/MS FAQ
1.How can I place an order for MCP7940MT-I/MS through Aetrix?
Please submit a Request for Quotation (RFQ) for MCP7940MT-I/MS 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 MCP7940MT-I/MS reliable?
The price and inventory of MCP7940MT-I/MS are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MCP7940MT-I/MS is usually 5 days.
3.What payment methods are accepted for MCP7940MT-I/MS?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MCP7940MT-I/MS transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MCP7940MT-I/MS?
MCP7940MT-I/MS orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MCP7940MT-I/MS 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 MCP7940MT-I/MS?
For technical support, including MCP7940MT-I/MS datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MCP7940MT-I/MS requirements.
6.How does Aetrix verify that MCP7940MT-I/MS is sourced from the original manufacturer or authorized distributors?
All MCP7940MT-I/MS 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 MCP7940MT-I/MS meets industry standards.
7.What is the process for return or replacement of MCP7940MT-I/MS?
All MCP7940MT-I/MS units undergo pre-shipment inspection (PSI). If there is an issue with MCP7940MT-I/MS, 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 MCP7940MT-I/MS part is unused and in its original packaging.
Return procedure for MCP7940MT-I/MS:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
MCP7940MT-I/MS Tags
-
MCP7940N-I/SN
Microchip Technology
-
MCP7940MT-I/MNY
Microchip Technology
-
PCF85063ATL/1,118
NXP USA Inc.
-
MCP7940NT-I/SN
Microchip Technology
-
MCP7940NT-I/MS
Microchip Technology
-
MCP7940N-I/MS
Microchip Technology
-
PCF85063AT/AY
NXP USA Inc.
-
PCF85063TP/1Z
NXP Semiconductors
-
PCF85063ATT/AJ
NXP USA Inc.
-
MCP7940NT-E/SN
Microchip Technology
-
MCP7940NT-I/MNY
Microchip Technology
-
MCP79400T-I/SN
Microchip Technology
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