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

STMicroelectronics M41ST87YMX6TR

Name: M41ST87YMX6TR
Brand: STMicroelectronics
SKU: M41ST87YMX6TR
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: M41ST87YMX6TR

Manufacturer:: STMicroelectronics

Category:: Real Time Clocks

Package:: 28-SOIC (0.295", 7.50mm Width)

Datasheet:: M41ST87YMX6TR.pdf

Description:: IC RTC CLOCK/CALENDAR I2C 28SO

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Product details

Overview

M41ST87YMX6TR from STMicroelectronics is a secure serial real-time clock (RTC) and non-volatile RAM (NVRAM) supervisor with integrated tamper detection, 128 bytes of clearable user NVRAM, dual power-fail comparators (VPFD ≈ 4.63 V / 4.37 V), and embedded 32.768 kHz crystal in SOX28 package. It provides timekeeping (century/year/month/date/hour/minute/second/tenths-hundredths), alarm interrupt, watchdog timer, battery-backed operation, and microprocessor power-on reset - deployed in industrial metering, secure access systems, and backup-critical instrumentation.

For engineers reviewing the M41ST87YMX6TR datasheet, M41ST87YMX6TR pinout, M41ST87YMX6TR application, or M41ST87YMX6TR equivalent, key selection criteria include tamper timestamping capability, VPFD voltage select via THS pin, ultra-low 500 nA battery supply current, I²C-compatible 400 kHz interface, and SOX28 package with embedded crystal for anti-tamper clock integrity.

Technical Context

The M41ST87YMX6TR implements a BCD-encoded RTC with automatic leap-year correction and century-bit support, synchronized to an internal 32.768 kHz oscillator stabilized by an embedded quartz crystal. Its two independent tamper inputs (TP1IN/TP2IN) support programmable polarity, sampling rate, and RAM-clear-on-tamper (CLR1/CLR2) with timestamped event logging in dedicated registers.

It integrates dual 1.25 V reference-based power-fail comparators (PFI1/PFI2) driving open-drain PFO1/PFO2 outputs, plus RSTIN1/RSTIN2 debounced reset inputs that generate a shared open-drain RST output. The I²C interface supports auto-increment addressing and operates up to 400 kHz with standard slave address 0xD0 (write) / 0xD1 (read).

Key Specifications

Parameter	Value and Actual Design Meaning
Supply Voltage	4.75–5.5 V (VCC); supports 5.0 V system rail with THS = 1 for VPFD ≈ 4.63 V power-fail threshold
I²C Interface	400 kHz max clock rate; 7-bit slave address 0x68 (0xD0 write / 0xD1 read); bidirectional SDA/SCL with auto-increment addressing
Tamper Detection	Dual independent inputs (TP1IN/TP2IN); timestamped event capture; programmable polarity/sampling; CLR1/CLR2-triggered NVRAM wipe
Battery Current	500 nA typical (VBAT mode); enables >10-year lithium coin-cell life for RTC + NVRAM retention
NVRAM Size	128 bytes of clearable general-purpose SRAM; separate from 8-byte serial number and 11-byte control/calibration RAM
Oscillator	Embedded 32.768 kHz crystal in SOX28 package; oscillator stop detection (OF bit) ensures clock validity monitoring
Power-On Reset	Integrated POR circuit generates active-low open-drain RST signal; also accepts external RSTIN1/RSTIN2 inputs

Pinout & Package

Package: SOX28 - 28-lead, 300-mil plastic small-outline IC with embedded 32.768 kHz crystal; lead finish: matte tin; RoHS-compliant.

Pin/Terminal	Circuit Role	Design Meaning
VCC	Main supply input	4.75–5.5 V nominal; powers RTC, NVRAM, and logic; switchover to VBAT occurs at VPFD threshold
VBAT	Battery backup supply	Connects to lithium coin cell (e.g., CR2032); sustains RTC/NVRAM during main power loss
SCL / SDA	I²C bus interface	Standard 2-wire serial interface; supports multi-master arbitration; pull-up required externally
IRQ/OUT	Interrupt/output pin	Open-drain output; asserts on alarm, watchdog timeout, or tamper event; configurable as general-purpose output
SQW/FT	Square wave/frequency test	Programmable output (open-drain or CMOS); delivers 1 Hz, 32.768 kHz, or other divided clocks per register setting
F32k	32 kHz square wave output	Open-drain; fixed 32.768 kHz output; used for external timing reference or calibration
TP1IN / TP2IN	Tamper detection inputs	Independent, programmable inputs; support normally open/closed switches; trigger timestamped RAM clear on event
TPCLR	Tamper RAM clear enable	Active-high input (SOX28 only); forces immediate wipe of 128-byte NVRAM upon tamper detection
PFI1 / PFI2	Power-fail comparator inputs	Monitor external rails; compare against internal 1.25 V reference; set VPFD thresholds via THS pin configuration
PFO1 / PFO2	Power-fail outputs	Open-drain outputs; assert low when corresponding PFI input drops below VPFD; drive external hold/reset circuits
RSTIN1 / RSTIN2	External reset inputs	Debounced, active-low inputs; generate combined RST output; tolerate slow edges and noise per internal filtering
RST	Reset output	Open-drain; active-low; asserted during power-on, power-fail, or external RSTIN assertion; requires external pull-up
VOUT	Regulated output	3.0 V ±5% regulated supply; powers external LPSRAM or sensors; current-limited to 5 mA
ECON	Conditioned chip enable	Open-drain output; mirrors internal chip enable state; used for external memory gating or power sequencing
WDI	Watchdog input	Edge-sensitive input; must be toggled within watchdog timeout period to prevent RST assertion

Key Features

Feature	Design Value
Embedded crystal oscillator	32.768 kHz quartz resonator integrated into SOX28 package - eliminates external crystal placement and routing vulnerability to physical tampering
Tamper timestamping	Hardware-acquired time-of-event stamp stored in dedicated registers - enables forensic audit trail without host CPU involvement
Clearable 128-byte NVRAM	User-accessible SRAM erased on tamper detection or via TPCLR pin - protects sensitive keys, logs, or calibration data from unauthorized extraction
Dual independent power-fail comparators	Two separate VPFD thresholds (selectable via THS pin) allow monitoring of primary and auxiliary rails - supports redundant power supervision in safety-critical systems
Full-time 32 kHz output (F32k)	Dedicated open-drain 32.768 kHz signal available continuously - usable as precision clock source for external ADCs, sensors, or communication peripherals
Electronic serial number	Factory-programmed 8-byte unique ID - enables device authentication, firmware binding, and secure provisioning in trusted execution environments

Applications

Smart Electricity Meter

Secure Access Control Panel

Use Scenario: Long-term energy billing with tamper-resistant time-stamping and secure log storage.

IC Role / Device Role / Timing Role: Primary RTC and secure NVRAM supervisor; maintains accurate calendar across power cycles and triggers NVRAM wipe on enclosure breach.

Use Value: Embedded crystal prevents oscillator manipulation; tamper timestamping satisfies utility regulatory requirements (e.g., ANSI C12.1, IEC 62053); 500 nA battery current extends meter lifetime beyond 15 years.

Use Scenario: Door lock controller requiring cryptographic key protection and intrusion event logging.

IC Role / Device Role / Timing Role: Secure time source and tamper-activated memory erasure unit; timestamps door-open attempts and clears credential storage on forced entry.

Use Value: Dual TP1IN/TP2IN inputs monitor both door sensor and enclosure switch; CLR1/CLR2 bits enable selective wipe of keys vs. audit logs; electronic serial number binds firmware to hardware.

Industrial PLC Backup Module

Medical Infusion Pump Timer

Use Scenario: Maintaining runtime counters, calibration data, and fault history during AC power interruption.

IC Role / Device Role / Timing Role: NVRAM supervisor for external LPSRAM; provides battery-backed timekeeping and power-fail signaling to initiate safe shutdown.

Use Value: VOUT pin supplies 3.0 V to external SRAM; PFO1/PFO2 drive PLC watchdog and status LEDs; auto-switchover ensures zero-clock-loss during brownouts.

Use Scenario: Precise dose timing and therapy session logging in battery-powered infusion devices.

IC Role / Device Role / Timing Role: Certified RTC with alarm interrupt and battery-low flag; drives audible/visual alerts at scheduled intervals and logs delivery events.

Use Value: BCD-encoded time registers simplify FDA-compliant audit trail generation; 500 nA battery draw maximizes single-battery operational life; oscillator stop detection prevents undetected clock failure.

Equivalent & Alternatives

The following parts are listed as comparable options for similar secure RTC and NVRAM supervisor applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
DS3231M+	Higher accuracy ±2 ppm TCXO (vs. ±20 ppm crystal); no embedded tamper inputs; 236 bytes NVRAM; I²C only	Lacks dual tamper detection, timestamping, and TPCLR-driven RAM wipe; better for precision timing where security is secondary	Select DS3231M+ when absolute time accuracy outweighs tamper forensics; avoid where regulatory tamper response is mandated
M41ST87WMX6TR	3.0/3.3 V variant; VPFD ≈ 2.9 V / 2.63 V; identical pinout/functionality except supply range and power-fail thresholds	Designed for 3 V systems (e.g., portable medical, battery-only IoT); not interoperable with 5 V rails due to lower VPFD	Choose M41ST87WMX6TR for new 3 V designs; M41ST87YMX6TR remains appropriate for legacy 5 V industrial infrastructure

Compared with DS3231M+, M41ST87YMX6TR offers hardware-enforced tamper response and embedded crystal isolation but trades off timing accuracy; versus M41ST87WMX6TR, it delivers higher VPFD thresholds essential for stable 5 V power supervision without false triggers.

Availability

M41ST87YMX6TR is available at Aetrix Electronics and suitable for smart metering, secure access systems, industrial PLC backup modules, and medical infusion pump timers requiring stable component supply, long-term lifecycle support, and anti-tamper certification compliance.

Supply support for M41ST87YMX6TR 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing analog, MCU, power, and sensing solutions for automotive, industrial, and consumer markets.

The M41ST87Y series belongs to ST's secure timekeeping product line, engineered specifically for applications demanding tamper-evident time stamping, battery-backed NVRAM supervision, and regulatory-compliant power-fail response in metering and critical infrastructure.

FAQ

What is the function of the THS pin on the M41ST87YMX6TR?

The THS (Threshold Select) pin configures the power-fail comparator threshold voltage: when THS = 1, VPFD ≈ 4.63 V (for VCC = 4.75–5.5 V); when THS = 0, VPFD ≈ 4.37 V (for VCC = 4.5–5.5 V). This allows precise alignment with system rail tolerances and avoids spurious power-fail assertions during nominal voltage ripple.

Does the M41ST87YMX6TR support external crystal operation?

No - the M41ST87YMX6TR is supplied exclusively in the SOX28 package with an embedded 32.768 kHz crystal. External crystal operation is only supported by the SSOP20 variant (e.g., M41ST87W), which uses XI/XO pins. Using an external crystal with the SOX28 package is not electrically or mechanically supported.

How does tamper detection trigger NVRAM clearing?

Tamper detection clears NVRAM via two independent paths: (1) software-controlled CLR1/CLR2 bits in tamper registers, or (2) hardware assertion of the TPCLR pin (SOX28 only). Both methods immediately erase all 128 bytes of user NVRAM while preserving the timestamped tamper event in dedicated registers for forensic analysis.

Is the F32k output available during battery backup mode?

Yes - the F32k pin delivers a continuous 32.768 kHz square wave output in both VCC-powered and VBAT-only modes. It remains active during power switchover and is unaffected by alarm, watchdog, or tamper states, making it a reliable timing reference for external low-power peripherals during backup operation.

M41ST87YMX6TR Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: 28-SOIC (0.295", 7.50mm Width)

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

Programmable:: Not Verified

Type:: Clock/Calendar

Features:: Alarm, Leap Year, NVSRAM, Square Wave Output, Supervisor, Watchdog Timer

Memory Size:: 128B

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

Date Format:: YY-MM-DD-dd

Interface:: I2C, 2-Wire Serial

Voltage - Supply:: 4.5V ~ 5.5V

Voltage - Supply, Battery:: 2.5V ~ 5.5V

Current - Timekeeping (Max):: 1mA @ 4.5V ~ 5.5V

Operating Temperature:: -40°C ~ 85°C

Mounting Type:: Surface Mount

Grade:: -

Qualification:: -

Supplier Device Package:: 28-SO

M41ST87YMX6TR FAQ

1.How can I place an order for M41ST87YMX6TR through Aetrix?

Please submit a Request for Quotation (RFQ) for M41ST87YMX6TR 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 M41ST87YMX6TR reliable?

The price and inventory of M41ST87YMX6TR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for M41ST87YMX6TR is usually 5 days.

3.What payment methods are accepted for M41ST87YMX6TR?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for M41ST87YMX6TR transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for M41ST87YMX6TR?

M41ST87YMX6TR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your M41ST87YMX6TR 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 M41ST87YMX6TR?

For technical support, including M41ST87YMX6TR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your M41ST87YMX6TR requirements.

6.How does Aetrix verify that M41ST87YMX6TR is sourced from the original manufacturer or authorized distributors?

All M41ST87YMX6TR 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 M41ST87YMX6TR meets industry standards.

7.What is the process for return or replacement of M41ST87YMX6TR?

All M41ST87YMX6TR units undergo pre-shipment inspection (PSI). If there is an issue with M41ST87YMX6TR, 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 M41ST87YMX6TR part is unused and in its original packaging.

Return procedure for M41ST87YMX6TR:

1.Submit a request within 90 days.

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

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