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111899

NOT RECOMMENDED FOR NEW DESIGNS, SEE DS1321 DATASHEET INSTEAD.

FEATURES

Converts CMOS RAMs into nonvolatile

memories

Data is automatically protected during power loss

2-to-4 decoder provides for up to 4 CMOS

RAMs

Provides for redundant batteries

Test battery condition on power-up

Full ±10% operating range

Unauthorized access can be prevented with

optional security feature

16-pin 0.3-inch DIP saves PC board space

Optional 16-pin SOIC surface mount package

Optional industrial temperature range of

-40°C to +85°C available

PIN DESCRIPTION

A, B

- Address Inputs

CE

- Chip Enable Input

CE0

- Chip Enable Outputs

- + Battery 1

- + Battery 2

- Reset

- +5V Supply

- RAM Supply

- Read Inpu

- Write Input

*D/Q

- Data Input/Output

PIN ASSIGNMENT

*Used with optional security circuit only and must be connected to ground in all other cases.

DESCRIPTION

The DS1221 Nonvolatile Controller x 4 Chip is a CMOS circuit which solves the application problem of

converting CMOS RAMs into nonvolatile memories. Incoming power is monitored for an out-of-

tolerance condition.

When such a condition is detected, the chip enable outputs are inhibited to

accomplish write protection and the battery is switched on to supply RAMs with uninterrupted power. An

optional security code prevents unauthorized users from obtaining access to the memory space. The

nonvolatile controller/decoder circuitry uses a low-leakage CMOS process which affords precise voltage

detection at extremely low battery consumption. By combining the DS1221 with up to four CMOS

memories and lithium batteries, nonvolatile operation can be achieved.

DS1221

Nonvolatile Controller x 4 Chip

www.dalsemi.com

VCCO

VBAT1

*RST

A

B

*RD

*WE

GND

VCCI

VBAT2

CE0

CE2

CE3

*D/Q

CE

CE1

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

DS1221 16-Pin DIP (300-mil)

See Mech. Drawings Section

VCCO

VBAT1

*RST

A

B

*RD

*WE

GND

VCCI

VBAT2

CE0

CE2

CE3

*D/Q

CE

CE1

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

DS1221 16-Pin SOIC (300-mil)

See Mech. Drawings Section