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Microchip Technology MCP7940N-E/SN
- Part No.:
- MCP7940N-E/SN
- Manufacturer:
- Microchip Technology
- Category:
- Real Time Clocks
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
MCP7940N-E/SN.pdf
- Description:
- IC RTC CLK/CALENDAR I2C 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:7,499
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Product details
Overview
MCP7940N-E/SN from Microchip Technology is a battery-backed I²C Real-Time Clock/Calendar (RTCC) with integrated 64-byte SRAM, digital trimming (±1 ppm resolution), dual programmable alarms, and power-fail time-stamping. It operates from 1.8V–5.5V, draws only 1.2 µA at 3.3V for timekeeping, and supports 32.768 kHz crystal or external clock input.
For engineers reviewing the MCP7940N-E/SN datasheet, MCP7940N-E/SN pinout, MCP7940N-E/SN application, or MCP7940N-E/SN equivalent, this page delivers verified timing accuracy, low-power backup operation, alarm-triggered system wake-up, and I²C interface compatibility up to 400 kHz - all critical for industrial control, energy metering, and automotive infotainment design.
Technical Context
The MCP7940N-E/SN implements a fully autonomous RTCC using BCD-encoded time registers (seconds through year), leap-year compensation to 2399, and automatic rollover handling across date/month boundaries. Its oscillator circuit supports both 32.768 kHz tuning-fork crystals (optimized for 6–9 pF load capacitance) and external clock input via X1, with OSCRUN status flag and TOSF timeout detection.
Power management includes seamless switchover between VCC and VBAT (1.3–5.5V), with independent logging of power-loss and power-restore timestamps in dedicated registers (0x18–0x1F). The multifunction pin (MFP) serves as configurable alarm output, square-wave generator (selectable frequencies), or general-purpose open-drain output - all controlled via the CONTROL register (0x07).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Oscillator Frequency | 32.768 kHz - precisely matches standard quartz tuning-fork crystals for stable timebase generation |
| Timekeeping Current (VCC) | 1.2 µA at 3.3V - enables multi-year battery backup life in mains-powered systems with brownout resilience |
| Backup Current (VBAT) | 925 nA at 3.0V - minimizes coin-cell drain during extended power loss, preserving time and SRAM data |
| I²C Interface Speed | Up to 400 kHz - supports fast configuration and timestamp reads without blocking host MCU execution |
| Digital Trimming Range | ±129 ppm with ±1 ppm resolution - allows field calibration to compensate for crystal tolerance and temperature drift |
| Operating Temperature | −40°C to +125°C (Extended grade) - qualified for under-hood automotive and industrial environments |
| SRAM Capacity | 64 bytes battery-backed - retains critical system state, calibration data, or event logs during main power loss |
Pinout & Package
Package: 8-Lead SOIC (Small Outline Integrated Circuit), surface-mount, industry-standard footprint compatible with automated assembly.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| X1 | Crystal Input / External Clock Input | Accepts 32.768 kHz crystal or external clock signal; 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 enabled |
| VBAT | Battery Backup Supply | Provides power to RTCC and SRAM during VCC loss; switchover threshold is 1.3–1.7V (VTRIP) |
| VSS | Ground Reference | Common return path for all internal circuits; must be connected to system ground plane |
| SDA | I²C Bidirectional Data Line | Open-drain interface requiring external pull-up; handles address, command, and data transfer per I²C protocol |
| SCL | I²C Clock Input | Synchronizes all read/write operations; supports 100 kHz (1.8–2.5V) and 400 kHz (≥2.5V) modes |
| MFP | Multifunction Output Pin | Configurable as alarm assertion, square-wave output (1Hz/2Hz/4Hz/8Hz/16Hz/32Hz/64Hz/128Hz), or GPIO |
| VCC | Main Power Supply | Primary operating voltage (1.8–5.5V); powers logic, I²C interface, and oscillator when active |
Key Features
| Feature | Design Value |
|---|---|
| Dual Programmable Alarms | Two independent alarm modules (ALM0/ALM1) with maskable fields (seconds to month), enabling precise wake-up or interrupt scheduling |
| Power-Fail Time-Stamp | Automatically logs exact time of VCC loss and restoration in dedicated registers (0x18–0x1F), supporting forensic diagnostics and uptime accounting |
| On-Chip Digital Trimming | Adjusts oscillator frequency in ±1 ppm steps over ±129 ppm range - eliminates need for external trim capacitors or manual calibration |
| 12/24-Hour Mode Support | Configurable time format via RTCHOUR register bit; maintains correct day-of-week increment and leap-year logic regardless of mode |
| Leap-Year Compensation | Valid from 2001 to 2399 - handles February 29 correctly without firmware intervention, reducing host MCU overhead |
Applications
| Smart Energy Metering | Industrial PLC Control |
|---|---|
Use Scenario: Accurate billing interval tracking and tamper-detection timestamping in residential/commercial electricity meters. IC Role / Device Role / Timing Role: Primary timekeeping engine with battery-backed SRAM storing tariff schedules and outage history. Use Value: Maintains sub-second time accuracy over 10+ years on CR2032, enabling ISO/IEC 62053-compliant meter certification. |
Use Scenario: Synchronized event logging and scheduled maintenance alerts in factory automation controllers. IC Role / Device Role / Timing Role: Standalone RTCC providing deterministic timestamping for I/O transitions and fault events. Use Value: Eliminates host CPU polling for time updates; dual alarms trigger preventive maintenance cycles without software overhead. |
| Automotive Infotainment | Medical Diagnostic Equipment |
Use Scenario: Preserving clock and user settings (e.g., radio presets, navigation history) during vehicle ignition-off periods. IC Role / Device Role / Timing Role: AEC-Q100 qualified timing source with extended temperature support (−40°C to +125°C). Use Value: Guarantees reliable time continuity across cold cranking and thermal cycling, meeting OEM functional safety requirements. |
Use Scenario: Recording procedure start/end times and calibration validity windows in portable ultrasound or ECG devices. IC Role / Device Role / Timing Role: Low-power timekeeper maintaining audit trail integrity during battery-only operation. Use Value: 925 nA VBAT current extends single-charge runtime by >3 months, satisfying IEC 62304 traceability mandates. |
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 | Integrated TCXO (±2 ppm accuracy), higher timekeeping current (3 µA), no SRAM, different I²C address (0x68) | Better accuracy in wide-temperature environments but lacks battery-backed memory and power-fail timestamping | Choose DS3231SN#T&R when absolute time accuracy outweighs SRAM retention and diagnostic logging needs |
| PCF8563T/2,118 | No digital trimming, no power-fail timestamp, lower max I²C speed (100 kHz), 200 nA VBAT current | Lower cost and ultra-low backup current, but requires external calibration and offers no failure-event logging | Choose PCF8563T/2,118 for cost-sensitive consumer devices where basic timekeeping suffices and diagnostics are not required |
Compared with DS3231SN#T&R and PCF8563T/2,118, the MCP7940N-E/SN uniquely combines programmable alarms, 64-byte SRAM, power-fail time-stamping, and on-chip digital trimming - making it optimal for applications demanding both time fidelity and system-level event forensics.
Availability
MCP7940N-E/SN is available at Aetrix Electronics and suitable for smart energy metering, industrial PLC control, and automotive infotainment requiring stable component supply, long-term lifecycle assurance, and AEC-Q100 compliance.
Supply support for MCP7940N-E/SN 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 components, and timing solutions, serving automotive, industrial, and communications markets since 1989.
The MCP7940N product line delivers highly integrated, low-power RTC/Calendar ICs with battery-backed memory and advanced time-stamping features - designed specifically for mission-critical embedded systems needing deterministic timekeeping and failure diagnostics.
FAQ
What is the backup supply voltage range supported by the MCP7940N-E/SN?
The MCP7940N-E/SN supports a backup supply voltage range of 1.3V to 5.5V on the VBAT pin. Switchover from VCC to VBAT occurs when VCC drops below the VTRIP threshold (1.3–1.7V), ensuring uninterrupted timekeeping and SRAM retention. This range accommodates common coin cells (e.g., CR2032 at 3.0V) and supercapacitors.
Does the MCP7940N-E/SN require external load capacitors for its 32.768 kHz crystal?
Yes, the MCP7940N-E/SN requires external load capacitors on X1 and X2 pins when using a 32.768 kHz crystal. It is optimized for crystals with 6–9 pF load capacitance. Capacitor values must be selected to match the crystal's specified CL, accounting for PCB stray capacitance, per Equation 5-1 in the datasheet. Omitting them causes frequency inaccuracy or oscillator failure.
How does the power-fail time-stamp feature work in the MCP7940N-E/SN?
The MCP7940N-E/SN automatically logs the exact time of VCC loss (in PWRDN* registers) and VCC restoration (in PWRUP* registers) using its internal counters. These timestamps are stored in battery-backed memory and remain accessible after power recovery. This enables root-cause analysis of brownouts and validates system uptime compliance in regulated equipment.
Can the MCP7940N-E/SN operate without a crystal?
Yes, the MCP7940N-E/SN can operate using an external 32.768 kHz clock source applied to the X1 pin, with X2 left floating. The EXTOSC bit in the CONTROL register (0x07) must be set to enable this mode. This bypasses the internal oscillator circuit and eliminates crystal-related layout constraints while retaining full RTCC functionality.
What is the I²C address of the MCP7940N-E/SN and how is it configured?
The MCP7940N-E/SN uses a fixed 7-bit I²C client address of 0x6F (1101111x), where the LSB is the R/W bit. Unlike some RTCs, it has no hardware address pins - the address is non-configurable. The device acknowledges only addresses matching this pattern, and ignores all others, simplifying bus arbitration in multi-device systems.
MCP7940N-E/SN Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm 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:
- 1.3V ~ 5.5V
- Current - Timekeeping (Max):
- 1.2µA @ 3.3V
- Operating Temperature:
- -40°C ~ 125°C
- Mounting Type:
- Surface Mount
- Grade:
- Automotive
- Qualification:
- AEC-Q100
- Supplier Device Package:
- 8-SOIC
MCP7940N-E/SN FAQ
1.How can I place an order for MCP7940N-E/SN through Aetrix?
Please submit a Request for Quotation (RFQ) for MCP7940N-E/SN 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 MCP7940N-E/SN reliable?
The price and inventory of MCP7940N-E/SN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MCP7940N-E/SN is usually 5 days.
3.What payment methods are accepted for MCP7940N-E/SN?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MCP7940N-E/SN transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MCP7940N-E/SN?
MCP7940N-E/SN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MCP7940N-E/SN 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 MCP7940N-E/SN?
For technical support, including MCP7940N-E/SN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MCP7940N-E/SN requirements.
6.How does Aetrix verify that MCP7940N-E/SN is sourced from the original manufacturer or authorized distributors?
All MCP7940N-E/SN 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 MCP7940N-E/SN meets industry standards.
7.What is the process for return or replacement of MCP7940N-E/SN?
All MCP7940N-E/SN units undergo pre-shipment inspection (PSI). If there is an issue with MCP7940N-E/SN, 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 MCP7940N-E/SN part is unused and in its original packaging.
Return procedure for MCP7940N-E/SN:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
MCP7940N-E/SN 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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