M41T65Q6F - Serial RTC with Alarm, I2C, 1.3V-3.6V | STMicroelectronics
MPN: M41T65Q6F ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $2.85 | $2.85 |
| 10 | $2.61 | $26.10 |
| 100 | $2.28 | $228.00 |
| 500 | $2.04 | $1,020.00 |
| 1,000 | $1.83 | $1,830.00 |
M41T65Q6F Overview
A Real-Time Clock (RTC) is a category of low-power timing IC that maintains accurate wall-clock time and date information independent of the system microcontroller. RTCs are essential components in any battery-backed system that must preserve time-of-day across power cycles. The M41T65 belongs to the RTC IC > Clock/Calendar > I2C RTC sub-family, and within ST's product hierarchy it sits under Timekeeping ICs > Serial RTC > RTC with Alarms. RTCs bridge the gap between digital logic and physical time by using a 32.768 kHz crystal oscillator as the time-base reference and counting oscillator cycles to derive seconds, minutes, hours, and calendar days.
Key features of the M41T65Q6F include a wide operating voltage range of 1.3 V to 3.6 V (suitable for direct battery backup operation), integrated alarm and interrupt functions, a programmable square-wave output derived from the 32.768 kHz crystal, low power consumption typically below 1 microamp in battery backup mode, and an automatic backup switchover when VCC falls below a defined threshold. The 16-pin VQFN-EP (QFN-16) exposed-pad package provides low thermal resistance for stable operation across the -40 °C to +85 °C industrial temperature range and supports automated PCB assembly.
Architecturally, the M41T65Q6F combines a 32.768 kHz crystal oscillator, frequency divider chain, BCD-coded time/date registers, I2C interface logic, alarm comparators, and a trickle charger circuit. The internal oscillator drives a divider that produces 1-second resolution. Time and date are stored in Binary-Coded Decimal (BCD) format for direct display compatibility. The integrated trickle charger allows the device to recharge an external backup supercapacitor or rechargeable battery when main power is present, then automatically switch over to backup supply on VCC failure.
Typical applications include metering and data-logging systems, industrial controllers requiring time-stamped events, point-of-sale (POS) terminals, medical devices needing scheduled dosing or data recording, consumer electronics with calendar/alarm functions, and any battery-backed embedded system that needs to wake the host MCU at scheduled times. The low 1.3 V minimum supply also makes the M41T65Q6F well-suited for single-cell battery systems.
When designing with the M41T65Q6F, ensure the 32.768 kHz crystal load capacitance matches the datasheet specification (typically 12.5 pF) and place the crystal traces as short and symmetric as possible to minimize parasitic capacitance. A decoupling capacitor of 0.1 microfarad should be placed within 2 mm of the VCC pin. The exposed pad (EP) must be soldered to the ground plane for mechanical and thermal reliability.
This page synthesizes distributor pricing, package-equivalent alternatives in the same ST M41Txx RTC family, and practical design notes not aggregated on the manufacturer datasheet PDF.
Drop-in alternatives for M41T65Q6F — 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 M41T65Q6F (same form factor and footprint) — differing in Function, Interface, Operating Temperature, Package.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
M41T64Q6F
✅ Drop-In📋 Reference alternative (not in catalog)
M41T60Q6F
✅ Drop-In📋 Reference alternative (not in catalog)
M41T62Q6F
✅ Drop-In📋 Reference alternative (not in catalog)
M41T65Q6F Specifications
| Function | Real-Time Clock (RTC) with Alarm |
| Clock/Calendar Format | HH:MM:SS / Day-Date-Month-Year-Century (BCD) |
| Interface | I2C (2-Wire Serial), up to 400 kHz |
| Supply Voltage (VCC) | 1.3 V to 3.6 V |
| Timekeeping Current | Typical <1 µA (battery backup mode) |
| Crystal Frequency | 32.768 kHz (external) |
| Crystal Load Capacitance | 12.5 pF (typical, per datasheet) |
| Alarm / Interrupt | Yes (programmable) |
| Square-Wave Output | Programmable (32.768 kHz / 1 Hz) |
| Backup Battery Switchover | Automatic with integrated trickle charger |
| Operating Temperature | -40 °C to +85 °C |
| Package | 16-VFQFN Exposed Pad (QFN-16 EP) |
| Mounting Type | Surface Mount |
| Leap-Year Compensation | Automatic through year 2100 |
| RoHS Status | Compliant |
M41T65Q6F Pin Configuration
| Pin 1 | XOUT — 32.768 kHz crystal oscillator output |
| Pin 2 | XIN — 32.768 kHz crystal oscillator input |
| Pin 3 | VBAT — Backup battery supply input (trickle-charged) |
| Pin 4 | VCC — Main supply voltage (1.3 V to 3.6 V) |
| Pin 5 | SQW — Programmable square-wave / 32.768 kHz output |
| Pin 6 | IRQ/INT — Interrupt or alarm output (active low) |
| Pin 7 | SCL — I2C serial clock input |
| Pin 8 | SDA — I2C serial data (open-drain) |
| Pin 9 | GND — Ground |
| Pin 10 | NC — Not connected (per datasheet) |
| Pin 11 | NC — Not connected (per datasheet) |
| Pin 12 | NC — Not connected (per datasheet) |
| 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) |
| Pin EP | EP — Exposed thermal pad - solder to ground |
Typical Applications
M41T65Q6F is suitable for 7 applications: Industrial Data Loggers and Metering, Point-of-Sale Terminals, Medical Infusion Pumps and Diagnostic Devices, Battery-Backed Security and Access-Control Panels, Consumer Electronics with Calendar Functions, Server and Networking Time-of-Day Backup, IoT Sensor Nodes with Time Sync.
Industrial Data Loggers and Metering
The M41T65Q6F provides accurate time stamping for industrial data loggers, energy meters, and utility recorders where every measurement event must be tagged with a precise wall-clock timestamp. The 1.3 V minimum supply and integrated trickle charger allow the device to maintain time from a single lithium coin cell across multi-year deployments, while the 32.768 kHz oscillator delivers ±5 ppm typical accuracy, sufficient for most metering regulatory requirements. The programmable alarm can wake the host MCU to capture periodic samples, drastically reducing system power consumption. Its 16-QFN exposed-pad package also fits compact meter form factors used in DIN-rail installations.
Recommended
Point-of-Sale Terminals
POS terminals require precise date and time stamping of every transaction for accounting, auditing, and legal compliance. The M41T65Q6F's I2C interface integrates easily with the terminal's main ARM Cortex processor, while its wide 1.3 V to 3.6 V supply range simplifies integration with both the 3.3 V logic rail and a coin-cell backup that retains transaction logs during power loss. The integrated alarm and square-wave output can drive scheduled end-of-day archival tasks. Compared to MCUs with built-in RTCs, an external M41T65Q6F provides higher timekeeping accuracy and survives main-board power-down events.
Recommended
Medical Infusion Pumps and Diagnostic Devices
Medical infusion pumps, blood-pressure monitors, and diagnostic analyzers must time-stamp every dosing or measurement event for regulatory traceability and patient-safety records. The M41T65Q6F's ±5 ppm accuracy over -40 °C to +85 °C provides the timekeeping integrity required by IEC 60601-1 and FDA 21 CFR Part 11 audit trails. Its low standby current of less than 1 microamp extends battery runtime on portable infusion pumps during ambulatory operation, while the integrated alarm function can wake the host MCU at scheduled infusion intervals. The 16-QFN package is small enough to fit inside hand-held medical device enclosures.
Recommended
Battery-Backed Security and Access-Control Panels
Access-control panels, alarm systems, and intrusion-detection units must maintain accurate time during AC power loss to log door events correctly. The M41T65Q6F's integrated backup-battery switchover and trickle charger ensure the clock keeps running seamlessly when mains power drops, with no software intervention required. The 32.768 kHz crystal-accurate timebase also drives the SQW output, which can be used to wake the panel MCU every second to check sensors. The wide -40 °C to +85 °C operating range and QFN-16 form factor are well suited to wall-mounted security enclosures.
Recommended
Consumer Electronics with Calendar Functions
Smart speakers, digital photo frames, programmable thermostats, and kitchen appliances with scheduled cooking all rely on an RTC to maintain wall-clock time across power cycles. The M41T65Q6F's 1.3 V minimum supply makes it ideal for single-cell battery products, while its I2C interface glues directly to the main consumer MCU without extra glue logic. The programmable square-wave output simplifies LED-blink or wake-up timing on appliances, and the integrated century-tracking register eliminates the Y2K-style rollover risk through the year 2100.
Recommended
Server and Networking Time-of-Day Backup
Routers, switches, and edge servers use an external RTC like the M41T65Q6F to retain accurate time-of-day during power outages, complementing the less accurate internal RTCs on most SoCs. The M41T65Q6F's ±5 ppm typical accuracy is sufficient for syslog timestamping and TLS certificate validation windows. Its 1.3 V minimum supply allows operation directly from a coin-cell backup, and the integrated trickle charger keeps the backup topped up whenever main 3.3 V is present. The QFN-16 EP package is compatible with high-density networking PCB layouts.
Recommended
IoT Sensor Nodes with Time Sync
Battery-powered IoT sensor nodes in agriculture, environmental monitoring, and smart-city deployments use the M41T65Q6F to time-stamp sensor readings, drive deep-sleep wake cycles, and synchronize mesh-network time slots. The sub-microamp backup current extends node lifetime beyond 5 years on a single coin cell, while the wide operating temperature range supports outdoor enclosures. The I2C interface connects to virtually any low-power MCU including Cortex-M0+ and RISC-V parts, and the small 16-QFN footprint suits miniature sensor node PCBs.
Recommended
Recommended Products Summary
Engineering reference data for M41T65Q6F — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | M41T64Q6F | M41T60Q6F | M41T62Q6F |
|---|---|---|---|---|
| Brand | STMicroelectronics | STMicroelectronics | STMicroelectronics | STMicroelectronics |
| Package | 16-VFQFN Exposed Pad (QFN-16 EP) | 16-VFQFN Exposed Pad - same | 16-VFQFN Exposed Pad - same | 16-VFQFN Exposed Pad - same |
| Supply Voltage (VCC) | 1.3 V to 3.6 V | 1.8 V to 5.5 V | 2.0 V to 5.5 V | 2.5 V to 5.5 V |
| Interface | I2C (400 kHz) | I2C (400 kHz) | I2C (400 kHz) | I2C (400 kHz) |
| I2C Address | 0x68 | 0x68 | 0x68 | 0x68 |
| Backup Battery Switchover | Yes (with trickle charger) | Yes | Yes | Yes |
| Alarm / Interrupt | Yes | Yes | No (older generation) | Yes |
| Operating Temperature | -40 °C to +85 °C | -40 °C to +85 °C | -40 °C to +85 °C | -40 °C to +85 °C |
Key Differentiators
- Lowest minimum supply voltage in the ST M41T6x family (vs M41T64Q6F)
- Integrated alarm and interrupt function (vs M41T60Q6F)
- Wide supply range covering both 1.5 V and 3.3 V rails (vs M41T62Q6F)
Design Notes
Place the 32.768 kHz crystal within 5 mm of the XIN and XOUT pins and route the crystal traces as short, symmetric traces isolated from noisy digital lines like SDA, SCL, and high-current power paths. Add a ground guard ring around the crystal and oscillator pins to suppress coupled noise. A 0.1 microfarad decoupling capacitor must be placed within 2 mm of the VCC pin, and a 10 microfarad bulk capacitor near the IC is recommended for backup-battery switchover transients.
The integrated trickle charger supports external supercapacitor or rechargeable backup-battery operation. Connect a series diode or current-limiting resistor between VCC and VBAT as shown in the datasheet's typical application circuit; omitting this can cause backup-cell overcharge. The trickle-charger current is set by an external resistor and should be limited to roughly 1/1000 of the backup-battery capacity to comply with lithium-cell safety guidelines. When operating only with a primary (non-rechargeable) cell, disable the trickle charger by software register write.
Estimated: Total timekeeping error at +25 °C with a typical 12.5 pF load-capacitance crystal is about ±5 ppm, which equals roughly 13 seconds per month or 2.6 minutes per year. Engineers seeking higher accuracy should specify a tuning-fork crystal with ±10 ppm initial accuracy or perform a software trim using the M41T65Q6F's analog-trim register. Avoid placing the crystal over a ground cutout in an inner PCB layer, which raises its effective load capacitance and pulls the oscillator frequency.
Compliance Information
RoHS compliant per STMicroelectronics product page. Industrial -40 °C to +85 °C operating temperature. Not AEC-Q100 qualified - not intended for automotive safety-critical applications.
