Overview
The M41ST85WMH6F from STMicroelectronics is a multifunctional integrated circuit that combines a serial real-time clock (RTC), microprocessor supervisor, and NVRAM supervisor. Built using a low-power CMOS SRAM process, this device offers a comprehensive set of features for timekeeping, power management, and memory supervision. It includes a 400 kHz I²C serial interface, automatic backup battery switchover, and write protection for both internal RTC and external low power SRAM (LPSRAM). The device is designed to operate within a voltage range of 2.7 to 3.6 V and is RoHS compliant, making it suitable for a wide range of industrial and embedded applications.
Key Specifications
| Parameter | Value | Unit |
|---|---|---|
| Operating Voltage | 2.7 to 3.6 | V |
| I²C Interface Frequency | 400 kHz | |
| NVRAM Size | 44 bytes | |
| RTC Registers | 20 memory-mapped | |
| Oscillator Frequency | 32.768 kHz | |
| Battery Supply Current | 500 nA (max) | |
| Operating Temperature | -40°C to +85°C | |
| Package Options | 28-lead SNAPHAT® IC (SOH28), 28-lead embedded crystal SOIC (SOX28) |
Key Features
- Automatic battery switchover and WRITE protect for internal serial RTC and external LPSRAM
- 400 kHz I²C serial interface
- Ultralow battery supply current of 500 nA (max)
- RoHS compliant and lead-free second level interconnect
- Serial RTC with counters for seconds, minutes, hours, day, date, month, and year
- Programmable alarm with repeat modes and power-down timestamp (HT bit)
- Programmable watchdog with 62.5 ms to 128 s time-out period
- Early power-fail warning circuit (PFI/PFO) with 1.25 V precision reference
- Power-on reset/low voltage detect with open drain reset output
- Programmable squarewave generator (1 Hz to 32 kHz)
- Battery monitor (battery low flag)
Applications
The M41ST85WMH6F is suitable for a variety of applications requiring precise timekeeping, power management, and memory supervision. These include:
- Industrial control systems
- Embedded systems
- Medical devices
- Automotive systems
- Consumer electronics requiring real-time clock functionality
Q & A
- What is the primary function of the M41ST85WMH6F?
The M41ST85WMH6F is a combination serial real-time clock, microprocessor supervisor, and NVRAM supervisor.
- What is the operating voltage range of the M41ST85WMH6F?
The operating voltage range is 2.7 to 3.6 V.
- What type of interface does the M41ST85WMH6F use for communication?
The device uses a 400 kHz I²C serial interface.
- How much NVRAM does the M41ST85WMH6F have?
The device has 44 bytes of general-purpose NVRAM.
- What is the purpose of the automatic battery switchover feature?
The automatic battery switchover feature ensures that the internal RTC and external LPSRAM remain powered during system power failures.
- Does the M41ST85WMH6F support programmable alarms?
Yes, the device supports programmable alarms with repeat modes.
- What is the role of the watchdog timer in the M41ST85WMH6F?
The watchdog timer can be programmed to generate a reset output after a specified time-out period (62.5 ms to 128 s).
- How does the power-on reset function work?
The power-on reset function includes low voltage detection and generates an open drain reset output.
- What are the package options available for the M41ST85WMH6F?
The device is available in 28-lead SNAPHAT® IC (SOH28) and 28-lead embedded crystal SOIC (SOX28) packages.
- Is the M41ST85WMH6F RoHS compliant?
Yes, the device is RoHS compliant and has a lead-free second level interconnect.
