Functional Description

When power is valid, the bq4014 operates as a standard

CMOS SRAM. During power-down and power-up cycles,

the bq4014 acts as a nonvolatile memory, automatically

protecting and preserving the memory contents.

Power-down/power-up control circuitry constantly

use in systems with 5% supply tolerance. The bq4014Y

10% supply tolerance.

automatically write-protects the data.

All outputs

become high impedance, and all inputs are treated as

“don’t care.” If a valid access is in process at the time of

power-fail detection, the memory cycle continues to com-

pletion.

If the memory cycle fails to terminate within

circuitry switches to the internal lithium backup supply,

processor stabilization. Normal memory operation may

resume after this time.

The internal coin cells used by the bq4014 have an

extremely long shelf life and provide data retention for

more than 10 years in the absence of system power.

As shipped from Benchmarq, the integral lithium cells

are electrically isolated from the memory. (Self-discharge

in this condition is approximately 0.5% per year.)

broken, and the lithium backup provides data retention

on subsequent power-downs.

bq4014/bq4014Y

Truth Table

Mode

CE

WE

OE

I/O Operation

Power

Not selected

H

X

X

High Z

Standby

Output disable

L

H

H

High Z

Active

Read

L

H

L

Active

Write

L

L

X

Active

Absolute Maximum Ratings

Symbol

Parameter

Value

Unit

Conditions

-0.3 to 7.0

V

-0.3 to 7.0

V

Operating temperature

0 to +70

°C

Storage temperature

-40 to +70

°C

Temperature under bias

-10 to +70

°C

Soldering temperature

+260

°C

For 10 seconds

Note:

Permanent device damage may occur if Absolute Maximum Ratings are exceeded. Functional operation

should be limited to the Recommended DC Operating Conditions detailed in this data sheet. Exposure to

conditions beyond the operational limits for extended periods of time may affect device reliability.

Sept. 1992

2