M41T94MQ6F - Serial RTC 44B NVRAM SPI 16-SOIC | STMicroelectronics
MPN: M41T94MQ6F ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $6.42 | $6.42 |
| 10 | $5.78 | $57.80 |
| 100 | $5.16 | $516.00 |
| 500 | $4.62 | $2,310.00 |
| 1,000 | $4.11 | $4,110.00 |
M41T94MQ6F Overview
A real-time clock (RTC) is a low-power integrated circuit that maintains accurate wall-clock time using a quartz crystal reference, even when the main system is powered down. RTCs sit within the broader hierarchy of clock-and-timing ICs, which include general-purpose timers, oscillators, and PLL/clock generators. Unlike MCU-internal time counters, dedicated RTC ICs add battery backup switchover, calendar logic, and non-volatile user memory that survives both system reset and loss of main supply.
Key features of the M41T94MQ6F include SPI serial interface, 44 bytes of battery-backed NVRAM (16 bytes general-purpose plus 8 bytes used by the clock/calendar), a RESET output pin that asserts a fixed-duration low pulse for system brown-out management, and an integrated 32 kHz oscillator with on-chip load capacitance. The device operates from 2.7 V to 5.5 V main supply and is specified for the industrial -40 °C to +85 °C temperature range.
Typical applications include metering (electricity/water/gas), point-of-sale terminals, data loggers, industrial controllers, and any embedded system that needs a tamper-resistant, battery-backed time stamp separate from the application MCU. Designers should add a lithium backup cell (or supercapacitor) to the VBAT pin and follow the crystal-layout guidance in the ST datasheet for long-term timekeeping accuracy.
Drop-in alternatives for M41T94MQ6F — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with M41T94MQ6F (same form factor and footprint) — differing in Function, Interface, Operating Temperature, Package.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
M41T94MQ6E
✅ Drop-In📋 Reference alternative (not in catalog)
M41T94MQ6TR
✅ Drop-In📋 Reference alternative (not in catalog)
M41T65Q6F
✅ Drop-In✓ In Stock
$1.83 / Unit
View Datasheet →M41T94MQ6F Specifications
| Function | Serial Real-Time Clock with NVRAM and Reset |
| Memory Size | 44 bytes NVRAM (64 x 8, 512 bits) |
| Time Format | Day/Date/Month/Year/Century, BCD |
| Counter Granularity | Tenths/Hundredths of seconds, Seconds, Minutes, Hours, Day, Date, Month, Year, Century |
| Interface | SPI (4-wire, serial peripheral interface) |
| SPI Clock Frequency | 2 MHz maximum |
| Operating Supply Voltage | 2.7 V to 5.5 V |
| Crystal Oscillator | 32,768 Hz with on-chip load capacitance 12.5 pF |
| Crystal Series Resistance | Up to 80 kΩ (high ESR supported) |
| Reset Output | Yes, open-drain active-low RESET pulse |
| NVRAM Endurance | Battery-backed SRAM |
| Operating Temperature | -40 °C to +85 °C (industrial) |
| Package | 16-pin SOIC (0.154", 3.90 mm width) |
| Mounting Type | Surface Mount |
| MSL Level | 1 (unlimited at <30 °C/85 % RH) |
| RoHS Status | Compliant |
| Lead-Free / Halogen-Free | Yes / Yes (by ST declaration) |
M41T94MQ6F Pin Configuration
| Pin 1 | XOUT — 32,768 Hz crystal output |
| Pin 2 | XIN — 32,768 Hz crystal input |
| Pin 3 | VCC — Main supply voltage |
| Pin 4 | VBAT — Backup battery / supercap supply |
| Pin 5 | GND — Ground |
| Pin 6 | RESET — Active-low open-drain reset output |
| Pin 7 | CS — SPI chip-select (active low) |
| Pin 8 | SCLK — SPI serial clock |
| Pin 9 | SDI — SPI serial data input |
| Pin 10 | SDO — SPI serial data output |
| Pin 11 | FT — Frequency test / calibration output |
| Pin 12 | SQW — Square-wave output (programmable) |
| Pin 13 | NC — Not connected (per datasheet) |
| Pin 14 | NC — Not connected (per datasheet) |
| Pin 15 | NC — Not connected (per datasheet) |
| Pin 16 | NC — Not connected (per datasheet) |
Typical Applications
M41T94MQ6F is suitable for 6 applications: Electricity / Water / Gas Metering, Point-of-Sale (POS) Terminal, Industrial Data Logger, Vending Machine Controller, White Goods / Appliance Control, Industrial Controller / PLC.
Electricity / Water / Gas Metering
The M41T94MQ6F provides a tamper-resistant battery-backed wall-clock time stamp for utility meters where the application MCU may lose mains power but the meter must still log interval readings with a real-world timestamp. With 44 bytes of NVRAM, the meter firmware can also stash short rolling buffers (last-bill totals, tamper flags) that survive main-power removal. The integrated 12.5 pF oscillator load eliminates external caps, simplifying the meter PCB. The RESET output is useful as a clean MCU power-on reset gated on the RTC rail coming up first. Industrial -40 °C to +85 °C operation covers outdoor cabinet temperatures at most deployment sites. SPI bus lets the metering MCU poll time without I2C addressing conflicts in multi-drop scenarios.
Recommended
Point-of-Sale (POS) Terminal
POS terminals require accurate wall-clock time for transaction timestamps, audit logs, and end-of-day reconciliation, even after the terminal is unplugged overnight. The M41T94MQ6F's VBAT switchover preserves time and 44 bytes of NVRAM used for the last transaction count and security nonce, while the RESET pin provides a clean system reset when the backup cell takes over. SPI bus operation up to 2 MHz lets the POS application MCU read the time without I2C contention with other peripherals on the same bus. The 16-SOIC footprint is small enough for the terminal mainboard, and the wide 2.7-5.5 V supply range lets it ride on a single 3.3 V or 5 V rail. ST's industrial grade supports terminal-environment temperature swings.
Recommended
Industrial Data Logger
Industrial data loggers sample sensors at fixed intervals and must stamp each record with an accurate wall-clock time even when the host MCU is in deep sleep. The M41T94MQ6F keeps time on its 32 kHz crystal while the logger sleeps, and the SPI bus wakes the MCU only when a new sample needs a timestamp. The 44-byte NVRAM can buffer the most recent sensor readings so the host MCU can flush them on wake, eliminating the need for a separate SRAM. The wide 2.7-5.5 V supply lets the part ride on a 24 V bus-derived rail, and -40 °C to +85 °C operation covers factory-floor temperature ranges. The integrated 12.5 pF oscillator load saves PCB area in compact logger modules.
Recommended
Vending Machine Controller
Vending machines need a reliable time source for scheduled pricing windows, freshness-date displays, and cashless-transaction logs. The M41T94MQ6F provides wall-clock accuracy backed by a coin cell that survives main-power loss, with 44 bytes of NVRAM available to store the last-cashless transaction ID and pricing-schedule markers. The RESET pin doubles as a system watchdog-style reset if the M41T94 detects a power brown-out, helping the vending controller recover gracefully. The 16-SOIC industrial-grade part operates from -40 °C to +85 °C, covering both refrigerated beverage machines and outdoor vending enclosures. SPI interface avoids I2C address collisions with the bill validator and coin acceptor on the same bus.
Recommended
White Goods / Appliance Control
Modern white goods (washing machines, dishwashers, ovens) need a real-time clock to drive delayed-start cycles, scheduling, and energy-metering features. The M41T94MQ6F provides wall-clock time that survives power-off, with 44 bytes of NVRAM available for storing the last-cycle parameters. The RESET pin can be used to sequence the appliance MCU through a clean power-on cycle when AC mains returns after an outage. The 16-SOIC industrial-temperature grade operates reliably in the hot, vibration-prone appliance environment. SPI bus connects directly to the appliance MCU without address-collision risk on a multi-master I2C bus.
Recommended
Industrial Controller / PLC
PLC and industrial-controller modules require a tamper-resistant wall-clock for event logs, scheduled I/O actions, and audit trails. The M41T94MQ6F provides battery-backed timekeeping and 44 bytes of NVRAM for the most-recent event record, surviving both AC loss and brown-out events. The RESET output of the M41T94 can drive the PLC's reset supervisor, giving a deterministic power-on sequence. Wide 2.7-5.5 V supply lets the part share a 24 V-derived 3.3 V or 5 V rail. The industrial -40 °C to +85 °C temperature range covers outdoor cabinet and factory-floor environments. The 16-SOIC package footprint is consistent with the ST M41T series, simplifying second-source qualification.
Recommended
Recommended Products Summary
Engineering reference data for M41T94MQ6F — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | M41T94MQ6E | M41T94MQ6TR | M41T81SM6F | M41T65Q6F |
|---|---|---|---|---|---|
| Brand | STMicroelectronics | STMicroelectronics | STMicroelectronics | STMicroelectronics | STMicroelectronics |
| Package | 16-SOIC (0.154", 3.90 mm) | 16-SOIC (same) | 16-SOIC (same) | 8-SOIC (smaller) | 16-SOIC (same) |
| Interface | SPI (4-wire, 2 MHz max) | SPI (same) | SPI (same) | I2C (different) | I2C (different) |
| NVRAM Size | 44 bytes (64 x 8) | 44 bytes | 44 bytes | 20 bytes | 64 bytes + embedded EEPROM |
| Reset Output | Yes (open-drain active-low) | Yes (same) | Yes (same) | No | No (watchdog input) |
| Crystal Load Capacitance | 12.5 pF integrated | 12.5 pF integrated | 12.5 pF integrated | 12.5 pF integrated | External |
| Operating Supply | 2.7 V to 5.5 V | 2.7 V to 5.5 V | 2.7 V to 5.5 V | 2.7 V to 5.5 V | 2.7 V to 5.5 V |
| Operating Temperature | -40 °C to +85 °C | -40 °C to +85 °C | -40 °C to +85 °C | -40 °C to +85 °C | -40 °C to +85 °C |
Key Differentiators
- Reset output pin combined with 44-byte NVRAM (vs M41T81SM6F)
- SPI bus with 2 MHz clock rate (vs M41T65Q6F)
- Integrated 12.5 pF oscillator load capacitance (vs M41T65Q6F)
Design Notes
Add a Schottky diode (e.g., BAT54C) between VCC and VBAT, or follow the reference circuit in the ST datasheet, so the backup coin cell does not feed current back into the main rail when VCC is present. The M41T94MQ6F's VBAT pin must see a defined voltage even when no backup cell is used (tie to VCC through a 1 MΩ resistor) so the part does not enter an indeterminate power-on state. Estimated: backup-cell life at typical 1 µA VBAT load and a 48 mAh CR2032 is around 5+ years, but verify against the worst-case Iq figure from the datasheet.
Keep the 32,768 Hz crystal traces short and symmetric. Route XIN and XOUT on the top layer, surrounded by a ground pour, with no signal traces crossing underneath the crystal traces. Place the crystal within 5 mm of the IC pins. The integrated 12.5 pF load capacitance tolerates typical Cylinder / surface-mount tuning-fork crystals with 12.5 pF nominal load; specifying a crystal with 6 pF or 20 pF will cause measurable frequency offset.
Do not enable SPI bursts faster than 2 MHz or faster than the VCC-derated maximum; read-timing violations cause silent data corruption in the time registers. When writing to the clock/calendar, always send a STOP or CS-high at the end of the write sequence, otherwise the write may be ignored. The RESET output is open-drain — an external pull-up resistor (typically 10 kΩ) is required for proper logic-high behavior, and never drive RESET from an external source (it is output-only).
Compliance Information
RoHS / lead-free per ST F-suffix release grade. AEC-Q100 not applicable (consumer/industrial RTC). Refer to ST material-composition declaration for lot-level confirmation.
