Overview
The M48T35AV TIMEKEEPER® RAM, produced by STMicroelectronics, is a highly integrated 32 Kbit x 8 non-volatile static RAM and real-time clock. This monolithic chip is designed to provide a battery-backed memory and real-time clock solution. It is available in two special packages: the 28-pin, 600 mil DIP CAPHAT™ package and the 28-pin, 330 mil SOIC package. The CAPHAT™ package houses the silicon, a quartz crystal, and a long-life lithium button cell in a single package, while the SOIC package allows for a separate SNAPHAT® housing containing the battery and crystal to be mounted after the surface mount process.
Key Specifications
| Parameter | Description | Value |
|---|---|---|
| Memory Size | 32 Kbit x 8 | 256 Kbit |
| Supply Voltage (VCC) | 3.0 to 3.6 V | |
| Power-Fail Deselect Voltage (VPFD) | 2.7 V to 3.0 V | |
| Operating Temperature | 0 to 70 °C | |
| Package Types | 28-pin DIP CAPHAT™, 28-pin SOIC | |
| Battery Life | At least 7 years when VCC is less than VSO | |
| Clock Accuracy | Automatically corrects for 28, 29, 30, and 31 day months, including leap years until 2100 | |
| Compliance | RoHS compliant, lead-free second level interconnect |
Key Features
- Integrated ultra-low power SRAM, real-time clock, power-fail control circuit, and battery.
- BYTEWIDE™ RAM-like clock access.
- BCD coded year, month, day, date, hours, minutes, and seconds.
- Battery low flag (BOK).
- Frequency test output for real-time clock.
- Automatic power-fail chip deselect and WRITE protection.
- Self-contained battery and crystal in the CAPHAT™ DIP package.
- SNAPHAT® housing (battery and crystal) is replaceable.
- Pin and function compatible with JEDEC standard 32 Kbit x 8 SRAMs.
Applications
The M48T35AV is suitable for a variety of applications requiring non-volatile memory and real-time clock functionality, such as:
- Industrial control systems.
- Medical devices.
- Aerospace and defense systems.
- Automotive systems.
- Consumer electronics requiring precise timekeeping and data retention.
Q & A
- What is the memory size of the M48T35AV?
The M48T35AV has a memory size of 32 Kbit x 8, which is equivalent to 256 Kbit.
- What are the package options for the M48T35AV?
The M48T35AV is available in two package types: the 28-pin DIP CAPHAT™ and the 28-pin SOIC.
- How does the power-fail protection work?
The M48T35AV has an automatic power-fail chip deselect and WRITE protection mechanism. When VCC falls below the battery backup switchover voltage (VSO), the control circuitry connects the battery to maintain data and clock operation.
- What is the battery life of the M48T35AV?
The internal button cell will maintain data in the M48T35AV for an accumulated period of at least 7 years when VCC is less than VSO.
- Is the M48T35AV RoHS compliant?
Yes, the M48T35AV is RoHS compliant with a lead-free second level interconnect.
- How does the real-time clock function?
The real-time clock stores the year, month, day, date, hours, minutes, and seconds in BCD format and automatically corrects for 28, 29, 30, and 31 day months, including leap years until 2100.
- Can the SNAPHAT® housing be replaced?
Yes, the SNAPHAT® housing containing the battery and crystal is replaceable.
- Is the M48T35AV compatible with standard SRAMs?
Yes, the M48T35AV is pin and function compatible with JEDEC standard 32 Kbit x 8 SRAMs.
- What happens during a power failure during a WRITE cycle?
A power failure during a WRITE cycle may corrupt data at the currently addressed location but does not jeopardize the rest of the RAM's content.
- How does the device handle transient noise spikes on VCC?
The device may respond to transient noise spikes on VCC that reach into the deselect window. Decoupling of the power supply lines is recommended.
