DS1218

Overview

The DS1218 is a CMOS nonvolatile controller designed to convert standard CMOS RAM into nonvolatile memory. It operates with a VCCI supply range of 4.5V to 5.5V and supports a VBAT battery supply between 2.5V and 3.5V. The device consumes less than 100nA in battery mode and features a maximum propagation delay of 10ns. Available in 8-pin PDIP or SO packages, it ensures data integrity by monitoring power conditions.

Feature Summary

• Converts CMOS RAM into nonvolatile memories
• Unconditionally write protects when VCC is out of tolerance
• Automatically switches to battery when power fail occurs

Applications

• Battery backup for static RAM
• Data retention systems requiring low leakage
• Power-fail detection circuits

Procurement Notes

Verify the specific package variant required, as the DS1218 is available in both 8-pin PDIP and 8-pin SO configurations. Confirm RoHS compliance status if applicable, indicated by the '+' suffix in part numbers such as DS1218+ or DS1218S+. Ensure compatibility with the target CMOS RAM's voltage requirements before procurement.

Selection Notes

Select the DS1218 when integrating external CMOS SRAM requires automatic nonvolatile functionality without complex logic. Consider the 8-pin footprint constraints and ensure the application environment stays within the 0°C to +70°C operating temperature range. Verify that the lithium battery voltage falls within the specified 2.5V to 3.5V window for proper comparator operation.

Part Context

The DS1218 belongs to the Maxim Integrated nonvolatile controller family, specifically engineered to manage power transitions for external memory devices. It addresses the common challenge of preserving volatile RAM data during power interruptions by providing seamless switching between main supply and backup battery sources.

Replacement Considerations

DS1218+

FAQ

How does the DS1218 detect a power failure?

It constantly monitors the VCC supply and uses a precision comparator to detect when VCCI falls to 1.26 times the battery voltage.

What is the maximum propagation delay for the chip enable signal?

The maximum propagation delay from CE input to CEO output is 10 ns.