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

Microchip Technology MCP795W21-I/ST

Name: MCP795W21-I/ST
Brand: Microchip Technology
SKU: MCP795W21-I/ST
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: MCP795W21-I/ST

Manufacturer:: Microchip Technology

Category:: Real Time Clocks

Package:: 14-TSSOP (0.173", 4.40mm Width)

Datasheet:: MCP795W21-I/ST.pdf

Description:: IC RTC CLK/CALENDAR SPI 14TSSOP

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Product details

Overview

MCP795W21-I/ST from Microchip Technology is a battery-backed SPI Real-Time Clock/Calendar (RTCC) IC with integrated 2 Kbit EEPROM, EUI-48™ MAC address, programmable watchdog timer, dual event detect modules, and digital trimming. It maintains time to hundredth-of-second resolution across -40°C to +85°C, logs power-fail/power-up timestamps, and operates from 1.8V–3.6V main supply or 1.3V–3.6V backup. Used in industrial metering, data loggers, and networked edge devices requiring traceable time-stamping.

For engineers reviewing the MCP795W21-I/ST datasheet, MCP795W21-I/ST pinout, MCP795W21-I/ST application, or MCP795W21-I/ST equivalent, key selection criteria include its ±1 ppm digital trim range, 1.0 µA VBAT timekeeping current, dual alarm assignment to IRQ/WDO pins, 128-bit protected EEPROM with EUI-48 preprogramming, and SPI interface compliance up to 5 MHz at 3.0V.

Technical Context

The MCP795W21-I/ST implements a fully autonomous RTCC using a 32.768 kHz crystal oscillator with on-chip digital trimming (±259 ppm range, ±1 ppm resolution) and automatic switchover between VCC and VBAT. Its timekeeping engine tracks hundredths of seconds through year (leap-year compensated to 2399) in BCD format and buffers register reads to prevent rollover errors.

It integrates three independent interrupt-capable peripherals: a programmable watchdog timer with dedicated WDO output, a high-speed event detect module for pulse counting, and a low-speed event detect module with configurable debounce. All alarms, event flags, and WDT overflow can be routed to either IRQ or WDO open-drain outputs via configuration registers.

Key Specifications

Parameter	Value and Actual Design Meaning
Time Resolution	Hundredth-of-second granularity with leap-year compensation through year 2399 - enables precise timestamping for regulatory-compliant logging.
Digital Trim Range	±259 ppm with ±1 ppm resolution - allows field calibration to compensate for crystal aging, temperature drift, and load capacitance mismatch.
Timekeeping Current	1.0 µA typical at 3.0V from VBAT - supports >10-year coin-cell battery life in always-on backup mode.
SPI Interface Speed	Up to 5 MHz at VCC ≥ 2.5V - ensures fast register access and EEPROM writes without MCU timing bottlenecks.
Protected EEPROM	128-bit area preprogrammed with EUI-48™ MAC address - provides globally unique, tamper-resistant node identification for IoT device onboarding.
Power-Fail Timestamp	Logs exact time of VCC loss and restoration in dedicated registers - delivers auditable power-interruption history for industrial diagnostics.
Event Detection	Dual modules: high-speed (pulse count) and low-speed (switch debounce with selectable period) - eliminates need for external debouncing circuitry or polling logic.

Pinout & Package

14-pin SOIC (3.9 mm × 8.7 mm) and TSSOP packages; RoHS-compliant, Pb-free, industrial temperature grade (-40°C to +85°C).

Pin/Terminal	Circuit Role	Design Meaning
X1	Crystal input / External clock input	Accepts 32.768 kHz crystal (6–9 pF load) or external clock; also serves as oscillator enable control point via ST bit.
X2	Crystal output	Completes crystal oscillator loop; must be left floating when external clock is used on X1.
VBAT	Backup supply input	Provides continuous power to RTCC and SRAM during VCC outage; supports 1.3V–3.6V range with <1.2 µA retention current.
WDO	Watchdog timer output	Open-drain output for WDT timeout pulses or alarm signals; requires external pull-up; configurable pulse width.
IRQ	Interrupt request output	Open-drain output for event detect flags or alarm signals; shares routing flexibility with WDO; requires external pull-up.
CS	Chip select input	Active-low SPI enable; initiates all operations; forces SO into high-impedance when deasserted to support multi-device buses.
VSS	Ground reference	Primary return path for digital and analog circuits; must be low-impedance and tied directly to system ground plane.
SO	Serial data output	Master-out slave-in (MOSI) SPI line; outputs MSb-first data after SCK falling edge; high-Z when CS high.
SI	Serial data input	Master-in slave-out (MISO) SPI line; latches instructions/addresses/data on SCK rising edge.
SCK	Serial clock input	Asynchronous SPI clock; defines timing for SI sampling and SO updates; max 5 MHz at 3.0V.
EVHS	High-speed event input	Direct connection to pulse sources (e.g., encoder outputs); triggers interrupt after programmable count threshold.
EVLS	Low-speed event input	Connects to mechanical switches; applies user-selectable debounce period before asserting interrupt flag.
CLKOUT	Programmable square-wave output	Configurable frequency output (1 Hz to 32.768 kHz); usable as system clock source or debug signal.
VCC	Main power supply	1.8V–3.6V operating range; powers all digital logic, EEPROM write cycles, and SPI interface; higher voltage improves noise immunity.

Key Features

Feature	Design Value
Dual programmable alarms	Independent alarm 0 and alarm 1 with maskable fields (hundredths/sec through month); assignable to IRQ or WDO outputs for flexible interrupt routing.
Power-fail timestamp logging	Automatically records exact time of VCC dropout and recovery in dedicated 8-byte timestamp registers - no firmware overhead required.
On-chip 2 Kbit EEPROM	Software write-protected, 8-byte page write capability, 1M endurance cycles - stores calibration data, configuration, or firmware metadata without external memory.
64-byte battery-backed SRAM	Retains user data across power cycles; shares address space with RTCC registers; accessible via same READ/WRITE SPI commands.
Configurable clock output	CLKOUT pin delivers selectable frequencies (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, 32768 Hz) - replaces discrete clock dividers.

Applications

Smart Energy Metering	Industrial Data Logger
Use Scenario: Utility-grade electricity meter recording consumption with tariff-based time-of-use billing and outage detection. IC Role / Device Role / Timing Role: Primary time source and power-interruption logger; provides auditable timestamps for every kWh reading and grid event. Use Value: Enables compliance with IEC 62053-21 and ANSI C12.20 standards via ±1 ppm trim accuracy and power-fail timestamping.	Use Scenario: Ruggedized environmental sensor node capturing temperature, humidity, and vibration at fixed intervals over years. IC Role / Device Role / Timing Role: Autonomous timekeeper and nonvolatile storage manager; maintains real-time schedule and stores calibration offsets in SRAM/EEPROM. Use Value: Eliminates MCU dependency for timekeeping, reduces sleep-mode current by offloading timestamp generation to hardware.
Networked Building Controller	Medical Diagnostic Equipment
Use Scenario: HVAC controller synchronizing zone schedules, demand-response events, and firmware update windows across distributed nodes. IC Role / Device Role / Timing Role: Time-of-day coordinator and secure node identifier; supplies EUI-48™ MAC for DHCP registration and TLS certificate binding. Use Value: Ensures deterministic scheduling across networked devices and satisfies HIPAA audit requirements for time-stamped event logs.	Use Scenario: Portable ultrasound or ECG unit requiring FDA-compliant timestamping of patient waveforms and diagnostic reports. IC Role / Device Role / Timing Role: Certified real-time clock with traceable power-loss history; maintains time integrity during battery swaps and AC interruptions. Use Value: Meets IEC 62304 software lifecycle requirements by providing immutable, battery-backed time stamps for all clinical data records.

Smart Energy Metering

Industrial Data Logger

Use Scenario: Utility-grade electricity meter recording consumption with tariff-based time-of-use billing and outage detection.

IC Role / Device Role / Timing Role: Primary time source and power-interruption logger; provides auditable timestamps for every kWh reading and grid event.

Use Value: Enables compliance with IEC 62053-21 and ANSI C12.20 standards via ±1 ppm trim accuracy and power-fail timestamping.

Use Scenario: Ruggedized environmental sensor node capturing temperature, humidity, and vibration at fixed intervals over years.

IC Role / Device Role / Timing Role: Autonomous timekeeper and nonvolatile storage manager; maintains real-time schedule and stores calibration offsets in SRAM/EEPROM.

Use Value: Eliminates MCU dependency for timekeeping, reduces sleep-mode current by offloading timestamp generation to hardware.

Networked Building Controller

Medical Diagnostic Equipment

Use Scenario: HVAC controller synchronizing zone schedules, demand-response events, and firmware update windows across distributed nodes.

IC Role / Device Role / Timing Role: Time-of-day coordinator and secure node identifier; supplies EUI-48™ MAC for DHCP registration and TLS certificate binding.

Use Value: Ensures deterministic scheduling across networked devices and satisfies HIPAA audit requirements for time-stamped event logs.

Use Scenario: Portable ultrasound or ECG unit requiring FDA-compliant timestamping of patient waveforms and diagnostic reports.

IC Role / Device Role / Timing Role: Certified real-time clock with traceable power-loss history; maintains time integrity during battery swaps and AC interruptions.

Use Value: Meets IEC 62304 software lifecycle requirements by providing immutable, battery-backed time stamps for all clinical data records.

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
MCP795W20-I/ST	Same package, pinout, and feature set but lacks preprogrammed EUI-48™ address in protected EEPROM; 2 Kbit EEPROM only.	Used where unique MAC addressing is not required; suitable for cost-sensitive designs with internal node ID management.	Select MCP795W20-I/ST if EUI-48™ is unnecessary and lower unit cost is prioritized.
DS3231M+	Higher accuracy (±2 ppm temp-compensated oscillator), integrated TCXO, but no event detect modules, no watchdog timer, and no protected EEPROM with MAC address.	Preferred for ultra-high-precision timing (e.g., scientific instrumentation) where auxiliary functions like event counting or secure node ID are secondary.	Choose DS3231M+ only when sub-ppm stability across temperature is critical and MCP795W21-I/ST's integrated peripherals are unused.

Compared with MCP795W20-I/ST, the MCP795W21-I/ST adds factory-programmed EUI-48™ for plug-and-play network identity; compared with DS3231M+, it trades absolute oscillator accuracy for integrated watchdog, dual event detection, and secure MAC storage - making it more suitable for embedded systems requiring robustness and identity assurance over raw timing precision.

Availability

MCP795W21-I/ST is available at Aetrix Electronics and suitable for smart energy metering, industrial data logging, networked building controllers, and medical diagnostic equipment requiring stable component supply, long-term lifecycle support, and traceable time-stamping capabilities.

Supply support for MCP795W21-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, mixed-signal, analog, and Flash-IP solutions, serving automotive, industrial, consumer, and communications markets with high-reliability semiconductor products.

The MCP795Wxx family is designed for embedded systems requiring autonomous, battery-backed timekeeping with integrated security, diagnostics, and system supervision - targeting applications where MCU offload, power-fail resilience, and device identity are critical design requirements.

FAQ

What is the primary function of the MCP795W21-I/ST in a system?

The MCP795W21-I/ST serves as a self-contained Real-Time Clock/Calendar (RTCC) with integrated 2 Kbit EEPROM, EUI-48™ MAC address, programmable watchdog timer, and dual event detection. It maintains accurate time across power cycles using VCC or VBAT, logs power-fail events, and relieves the host MCU from timekeeping, timestamping, and peripheral supervision tasks - enabling lower-power, more reliable system operation.

How does the MCP795W21-I/ST handle oscillator calibration?

The MCP795W21-I/ST uses on-chip digital trimming with ±259 ppm range and ±1 ppm resolution, adjustable via the OSCTRIM register. This compensates for crystal tolerance, aging, and temperature-induced frequency drift without external components. Calibration is retained in nonvolatile memory and applied automatically on power-up, ensuring consistent accuracy across the -40°C to +85°C industrial temperature range.

Can the MCP795W21-I/ST operate without an external crystal?

Yes - the MCP795W21-I/ST supports external clock input mode: a 32.768 kHz signal applied to the X1 pin disables the internal oscillator (via EXTOSC bit), and X2 is left floating. This allows use with precision oscillators or clock trees where crystal layout constraints or EMI concerns exist. The device retains all RTCC, alarm, and backup functionality in this mode.

What distinguishes the MCP795W21-I/ST from the MCP795W11-I/ST?

The MCP795W21-I/ST contains 2 Kbit EEPROM and is preprogrammed with an EUI-48™ MAC address in its 128-bit protected EEPROM block, whereas the MCP795W11-I/ST has only 1 Kbit EEPROM and the same EUI-48™. Both share identical pinout, package, temperature rating, and feature set - the key differentiator is EEPROM capacity and associated data storage headroom for firmware, calibration, or logging metadata.

How are alarms configured and routed on the MCP795W21-I/ST?

Alarms 0 and 1 are independently configured via dedicated registers (ALM0SEC through ALM0MTH and ALM1HSEC through ALM1MTH), supporting maskable comparison on hundredths-of-seconds through month. Each alarm's output can be assigned to either the IRQ or WDO pin via CONTROL register bits (ALM0PIN/ALM1PIN), enabling flexible interrupt handling - for example, routing alarm 0 to IRQ for scheduling and alarm 1 to WDO for system reset initiation.

MCP795W21-I/ST Specifications

Product attributes: Attribute value

Manufacturer:: Microchip Technology

Series:: -

Package/Case:: 14-TSSOP (0.173", 4.40mm Width)

Packaging:: Tube

Product Status:: Active

Programmable:: Not Verified

Type:: Clock/Calendar

Features:: Alarm, EEPROM, Leap Year, Square Wave Output, SRAM, Unique ID, Watchdog Timer

Memory Size:: 64B

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

Date Format:: YY-MM-DD-dd

Interface:: SPI

Voltage - Supply:: 1.8V ~ 3.6V

Voltage - Supply, Battery:: 1.3V ~ 3.6V

Current - Timekeeping (Max):: 1µA @ 1.8V ~ 5.5V

Operating Temperature:: -40°C ~ 85°C

Mounting Type:: Surface Mount

Grade:: -

Qualification:: -

Supplier Device Package:: 14-TSSOP

MCP795W21-I/ST FAQ

1.How can I place an order for MCP795W21-I/ST through Aetrix?

Please submit a Request for Quotation (RFQ) for MCP795W21-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 MCP795W21-I/ST reliable?

The price and inventory of MCP795W21-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 MCP795W21-I/ST is usually 5 days.

3.What payment methods are accepted for MCP795W21-I/ST?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MCP795W21-I/ST transactions.

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4.How is shipping managed for MCP795W21-I/ST?

MCP795W21-I/ST orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your MCP795W21-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 MCP795W21-I/ST?

For technical support, including MCP795W21-I/ST datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MCP795W21-I/ST requirements.

6.How does Aetrix verify that MCP795W21-I/ST is sourced from the original manufacturer or authorized distributors?

All MCP795W21-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 MCP795W21-I/ST meets industry standards.

7.What is the process for return or replacement of MCP795W21-I/ST?

All MCP795W21-I/ST units undergo pre-shipment inspection (PSI). If there is an issue with MCP795W21-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 MCP795W21-I/ST part is unused and in its original packaging.

Return procedure for MCP795W21-I/ST:

1.Submit a request within 90 days.

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

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