DS1221 Datasheet, PDF (1/8 Pages) Dallas Semiconductor – Nonvolatile Controller x 4 Chip

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 DESCRIPTION
A, B
- Address Inputs
CE
- Chip Enable Input
CE0 - CE3
V_BAT1
V_BAT2
- Chip Enable Outputs
- + Battery 1
- + Battery 2
* RST
V_CCI
V_CCO
- Reset
- +5V Supply
- RAM Supply
* RD
- Read Inpu
* WE
*D/Q
- Write Input
- Data Input/Output
PIN ASSIGNMENT
VCCO ¹
VBAT1 ²
16 _VCCI
15 _VBAT2
*RST ³
A4
14 _CE
13 CE0
B5
12 CE1
*RD ⁶
*WE ⁷
GND ⁸
11 _CE2
10 _CE3
9 _*D/Q
DS1221 16-Pin DIP (300-mil)
See Mech. Drawings Section
VCCO ¹
16 _VCCI
VBAT1 ²
15 _VBAT2
*RST ³
A4
14 CE
13 CE0
B5
12 CE1
*RD ⁶
11 _CE2
*WE ⁷
GND ⁸
10 _CE3
9 _*D/Q
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.
1 of 8
111899