DS1221
Nonvolatile Controller x 4 Chip
www.dalsemi.com
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 ASSIGNMENT
VCCO
VBAT1
*RST
A
B
*RD
*WE
GND
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
VCCI
VBAT2
CE
CE0
CE1
CE2
CE3
*D/Q
DS1221 16-Pin DIP (300-mil)
See Mech. Drawings Section
VCCO
VBAT1
*RST
A
B
*RD
*WE
GND
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
VCCI
VBAT2
CE
CE0
CE1
CE2
CE3
*D/Q
PIN DESCRIPTION
A, B
CE
CE0
-
CE3
V
BAT1
V
BAT2
*
RST
V
CCI
V
CCO
*
RD
*
WE
*D/Q
- Address Inputs
- Chip Enable Input
- Chip Enable Outputs
- + Battery 1
- + Battery 2
- Reset
- +5V Supply
- RAM Supply
- Read Inpu
- Write Input
- Data Input/Output
DS1221 16-Pin SOIC (300-mil)
See Mech. Drawings Section
*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.
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111899
DALLAS [ DALLAS SEMICONDUCTOR ]
