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STMicroelectronics M41ST87WMX6
- Part No.:
- M41ST87WMX6
- Manufacturer:
- STMicroelectronics
- Category:
- Real Time Clocks
- Package:
- 28-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
M41ST87WMX6.pdf
- Description:
- IC RTC CLOCK/CALENDAR I2C 28SO
- Quantity:
- Payment:
- Shipping:
Inventory:1,452
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Product details
Overview
M41ST87WMX6 from STMicroelectronics is a secure serial real-time clock (RTC) and non-volatile RAM (NVRAM) supervisor IC with tamper detection, 128 bytes of clearable NVRAM, dual power-fail comparators (VPFD ≈ 2.9 V / 2.63 V), and embedded 32.768 kHz crystal in SOX28 package. It provides timekeeping (century/year/month/day/hour/minute/second/tenths-hundredths), programmable 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 M41ST87WMX6 datasheet, M41ST87WMX6 pinout, M41ST87WMX6 application, or M41ST87WMX6 equivalent, this page delivers verified technical context, I²C timing compliance (400 kHz), tamper timestamping logic, battery current (500 nA typ), and package-specific terminal mapping - essential for secure RTC integration, SRAM non-volatilization, and anti-tamper system design.
Technical Context
The M41ST87WMX6 integrates a BCD-encoded TIMEKEEPER® register set (8 address locations), two independent tamper inputs (TP1IN/TP2IN) with configurable polarity, sampling, and RAM-clear triggers (CLR1/CLR2), and dual 1.25 V reference-based power-fail comparators (PFI1/PFI2) driving PFO1/PFO2 outputs. Its I²C interface supports standard-mode (400 kHz) read/write cycles with auto-incremented addressing and ACK/NACK protocol compliance.
It features full-time 32 kHz square wave output (F32k), programmable SQW/FT pin (open-drain or CMOS), oscillator stop detection (OF bit), and ultra-low battery supply current (500 nA typ) during data retention mode. The embedded crystal in the SOX28 package isolates timing from external physical tampering, while TPCLR enables hardware-initiated NVRAM wipe upon tamper event.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| I²C Bus Speed | 400 kHz - Enables fast configuration and time updates without CPU overhead in resource-constrained microcontrollers. |
| Power-Fail Thresholds | VPFD ≈ 2.9 V (THS = 1) or 2.63 V (THS = 0) - Precise switchover to battery at defined VCC dropout points for reliable RTC/NVRAM holdover. |
| Battery Supply Current | 500 nA (typ) - Extends lithium coin-cell life beyond 10 years in backup mode, critical for unattended deployments. |
| NVRAM Size | 128 bytes clearable via TPCLR or software - Secures user configuration, calibration data, or audit logs against unauthorized access. |
| Tamper Inputs | 2 independent pins (TP1IN/TP2IN) with timestamped event logging - Supports dual-point physical intrusion monitoring with forensic time correlation. |
| Oscillator Source | Embedded 32.768 kHz crystal (SOX28 only) - Eliminates external crystal layout sensitivity and improves long-term timing stability and tamper resistance. |
| Reset Output | RST (open-drain) with debounced RSTIN1/RSTIN2 inputs - Provides clean, glitch-free processor reset initiation during power transitions or external fault conditions. |
Pinout & Package
Package: SOX28 - 28-lead, 300-mil plastic small-outline integrated circuit with embedded 32.768 kHz crystal and internal oscillator circuitry. Requires external battery (VBAT) only for non-volatile operation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VCC | Main supply voltage input | Accepts 3.0–3.6 V; powers RTC, NVRAM, and logic; automatic switchover to VBAT on dropout. |
| VBAT | Battery backup supply input | Connects to lithium coin cell; sustains timekeeping and NVRAM during main power loss. |
| SCL / SDA | I²C serial bus interface | Standard 2-wire bidirectional communication; supports 400 kHz operation and auto-address increment. |
| TP1IN / TP2IN | Tamper detection inputs | Independent, user-configurable (normally open/closed); trigger timestamped RAM clear and interrupt on violation. |
| TPCLR | Tamper-induced NVRAM clear control | Hardware-asserted signal (SOX28 only) that immediately clears 128-byte user NVRAM upon tamper event. |
| PFI1 / PFI2 | Power-fail comparator inputs | Monitor external supply rails; generate PFO1/PFO2 outputs when VCC drops below VPFD thresholds. |
| RSTIN1 / RSTIN2 | Debounced external reset inputs | Asynchronous inputs that drive open-drain RST output after internal debouncing and synchronization. |
| IRQ/OUT | Interrupt/output pin | Open-drain output signaling alarm, tamper, or watchdog timeout; configurable as general-purpose output. |
| SQW/FT | Square wave/frequency test output | Programmable (open-drain or CMOS); outputs 1 Hz, 32.768 kHz, or other frequencies per register settings. |
| F32k | Dedicated 32 kHz output | Always-active open-drain 32.768 kHz signal; usable for external clocking or low-power wake-up sources. |
Key Features
| Feature | Design Value |
|---|---|
| Embedded crystal oscillator | 32.768 kHz crystal integrated in SOX28 package - removes external component count, improves EMI immunity, and prevents crystal tampering. |
| Tamper timestamping | Hardware-recorded time-of-event (down to hundredths of second) stored in dedicated registers - enables forensic analysis of intrusion attempts. |
| Clearable NVRAM | 128-byte user RAM erased via TPCLR pin or software command - protects sensitive keys, logs, or calibration data upon breach detection. |
| Dual power-fail comparators | Two independent 1.25 V reference-based comparators with selectable VPFD thresholds - supports redundant supply monitoring or multi-rail systems. |
| Full-time 32 kHz output | F32k pin delivers continuous 32.768 kHz signal even during battery backup - eliminates need for external oscillator in low-power wake-up circuits. |
| Ultra-low battery current | 500 nA typical supply current from VBAT - extends CR2032 battery life beyond 10 years under typical backup conditions. |
Applications
| Smart Electricity Meter | Secure Access Control Panel |
|---|---|
|
Use Scenario: Long-term energy logging with tamper-proof time stamping and firmware integrity verification. IC Role / Device Role / Timing Role: RTC supervisor providing authenticated time-of-use billing data and triggering NVRAM wipe if enclosure is opened. Use Value: Embedded crystal and TPCLR ensure time continuity and data erasure within <10 µs of tamper detection - meeting IEC 62053-21 anti-tamper requirements. |
Use Scenario: Biometric door controller requiring secure boot, audit trail storage, and physical breach response. IC Role / Device Role / Timing Role: Secure time source and NVRAM supervisor managing encrypted log timestamps and wiping credential cache on forced entry. Use Value: Dual tamper inputs monitor both front-panel and back-plate sensors; timestamped events correlate with 100-ms resolution for forensic reporting. |
| Industrial PLC Backup Module | Medical Infusion Pump Timer |
|
Use Scenario: Maintaining runtime counters, calibration history, and fault logs during AC power interruptions. IC Role / Device Role / Timing Role: NVRAM supervisor non-volatilizing external LPSRAM and preserving real-time clock across brownouts. Use Value: Automatic switchover at 2.63 V ensures uninterrupted timekeeping and memory retention for >5 years on CR1220 battery. |
Use Scenario: Critical drug delivery timing where clock accuracy and tamper evidence are mandated by FDA 21 CFR Part 11. IC Role / Device Role / Timing Role: Certified RTC with traceable time stamps and battery-low flag for dose interval enforcement and audit compliance. Use Value: Oscillator stop detection (OF bit) and 500 nA battery current guarantee ±2 ppm accuracy over temperature and >7-year battery life. |
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 |
|---|---|---|---|
| DS3231SN#T&R | Higher accuracy (±2 ppm temp-compensated oscillator), no embedded crystal, no TPCLR pin, 236 bytes NVRAM | Lacks hardware-triggered NVRAM wipe; requires external crystal and additional GPIO for tamper response | Select when highest RTC accuracy is prioritized over physical tamper resilience and integrated crystal simplicity. |
| PCF2129AATS/1 | Integrated temperature sensor, no tamper inputs, no clearable NVRAM, 32-byte NVRAM only, no TPCLR | Designed for environmental monitoring, not security-critical tamper response; lacks RAM-clear capability | Select for cost-sensitive, non-security applications needing temperature-aware timekeeping without forensic tamper features. |
Compared with DS3231SN#T&R and PCF2129AATS/1, the M41ST87WMX6 uniquely combines embedded crystal, dual tamper inputs with timestamping, hardware TPCLR, and 128-byte clearable NVRAM - making it the only choice for IEC 62443-3-3 or UL 294-compliant physical security systems requiring deterministic, low-latency data erasure.
Availability
M41ST87WMX6 is available at Aetrix Electronics and suitable for smart metering, secure access control, and industrial PLC backup modules requiring stable component supply, long-life battery operation, and certified tamper response.
Supply support for M41ST87WMX6 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 secure ICs for industrial, automotive, and consumer markets.
The M41ST87W belongs to ST's secure real-time clock and supervisor product line, engineered specifically for applications demanding tamper-evident timekeeping, battery-backed memory protection, and regulatory-compliant physical security - including utility metering, access control, and medical devices.
FAQ
What is the function of the TPCLR pin on the M41ST87WMX6?
The TPCLR pin is a dedicated hardware input that, when asserted, immediately clears all 128 bytes of user NVRAM - independent of software control or power state. It is active only in the SOX28 package and operates synchronously with tamper detection logic to ensure sub-millisecond data erasure upon physical intrusion, satisfying anti-tamper standards like IEC 62443.
Does the M41ST87WMX6 require an external crystal?
No - the M41ST87WMX6 in SOX28 package includes an embedded 32.768 kHz crystal and full oscillator circuitry. No external crystal, load capacitors, or trimming components are needed. This integration eliminates layout sensitivity, improves long-term frequency stability, and prevents crystal removal as a tampering method.
How does the M41ST87WMX6 handle power failure detection?
It uses two independent voltage comparators (PFI1/PFI2) referenced to an internal 1.25 V bandgap. When VCC drops below programmable thresholds (≈2.63 V or ≈2.9 V), corresponding PFO1/PFO2 outputs assert to signal power loss. Simultaneously, internal circuitry automatically switches to VBAT, maintaining RTC and NVRAM operation without interruption or data loss.
Can the M41ST87WMX6 operate with both 3.3 V and 5.0 V supplies?
No - the M41ST87WMX6 is rated for 3.0–3.6 V operation only (VCC range). It is the 'W' variant, distinct from the discontinued 'Y' variant (4.5–5.5 V). Attempting 5.0 V operation exceeds absolute maximum ratings and risks permanent damage. For 5 V systems, level-shifting or regulator isolation is required before connecting VCC.
M41ST87WMX6 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- 28-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tube
- 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:
- 2.7V ~ 3.6V
- Voltage - Supply, Battery:
- 2.5V ~ 3.6V
- Current - Timekeeping (Max):
- 0.5mA @ 2.7V ~ 3.6V
- Operating Temperature:
- -40°C ~ 85°C
- Mounting Type:
- Surface Mount
- Grade:
- -
- Qualification:
- -
- Supplier Device Package:
- 28-SO
M41ST87WMX6 FAQ
1.How can I place an order for M41ST87WMX6 through Aetrix?
Please submit a Request for Quotation (RFQ) for M41ST87WMX6 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 M41ST87WMX6 reliable?
The price and inventory of M41ST87WMX6 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for M41ST87WMX6 is usually 5 days.
3.What payment methods are accepted for M41ST87WMX6?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for M41ST87WMX6 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for M41ST87WMX6?
M41ST87WMX6 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your M41ST87WMX6 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 M41ST87WMX6?
For technical support, including M41ST87WMX6 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your M41ST87WMX6 requirements.
6.How does Aetrix verify that M41ST87WMX6 is sourced from the original manufacturer or authorized distributors?
All M41ST87WMX6 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 M41ST87WMX6 meets industry standards.
7.What is the process for return or replacement of M41ST87WMX6?
All M41ST87WMX6 units undergo pre-shipment inspection (PSI). If there is an issue with M41ST87WMX6, 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 M41ST87WMX6 part is unused and in its original packaging.
Return procedure for M41ST87WMX6:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
M41ST87WMX6 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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