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PDF DS1234 Data sheet ( Hoja de datos )
| Número de pieza | DS1234 | |
| Descripción | Conditional Nonvolatile Controller Chip | |
| Fabricantes | Dallas | |
| Logotipo |  |
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DS1234
DS1234
Conditional Nonvolatile Controller Chip
FEATURES
• Converts CMOS static RAMs into nonvolatile
memories
• Software-controlled write inhibit
• Software-controlled battery disconnect extends
battery life
• Unconditionally write protects when VCC is out of
tolerance
• Consumes less than 100 nA of battery current
• Power fail signal can be used to interrupt processor on
power failure
• Low forward voltage drop on the VCC switch
• Optional 16-pin SOIC surface mount package
PIN ASSIGNMENT
VCCO 1
14 VCCI
NC
CEI
WEI
CEO
WEO
GND
2
3
4
5
6
7
13 VBAT VCCO
1
16 VCCI
12 A3
11 A2
10 A1
9 A0
NC 2 15 VBAT
NC 3 14 NC
CEI 4 13 A3
WEI 5 12 A2
CEO 6 11 A1
WEO 7 10 A0
8 PF
GND
8
9 PF
DS1234 14-Pin DIP (300 MIL) DS1234S 16-Pin SOIC (300 MIL)
PIN DESCRIPTION
VCCO
NC
– RAM Supply
– No Connection
CEI – Chip Enable Input
WEI – Write Enable Input
CEO
– Chip Enable Output to RAM
WEO
– Write Enable Output to RAM
GND
– Ground
PF – Power Fail Output
A0-A3
– Address Inputs
VBAT
VCCI
– Battery Input
– +5V Supply
DESCRIPTION
The DS1234 is a CMOS circuit that converts CMOS
RAM into nonvolatile memory and adds two software
selectable switches. Incoming power is monitored for
an out-of-tolerance condition. When such a condition is
detected, chip enable and write enable to the RAM are
inhibited to accomplish write protection, and the battery
is switched on to supply the memory with uninterrupted
power. The two software selectable switches provided
by the DS1234 are capable of inhibiting both the write
enable to the RAM and the battery backup circuitry by a
pattern recognition sequence across four address lines.
Inhibiting the write enable to the nonvolatile RAM pro-
vides data integrity by isolating the memory contents
from external change. The second switch provides add-
ed flexibility and increases battery life to the system by
enabling/disabling the battery for shipment or storage,
or when battery backup is not needed.
ECopyright 1995 by Dallas Semiconductor Corporation.
All Rights Reserved. For important information regarding
patents and other intellectual property rights, please refer to
Dallas Semiconductor databooks.
010692 1/7
1 page  
CAPACITANCE
PARAMETER
Input Capacitance
Output Capacitance
SYMBOL
CIN
COU
MIN
AC ELECTRICAL CHARACTERISTIC
PARAMETER
SYMBOL
Address Setup
Address Hold
Read Recovery
CEI Pulse Width
Propagation Delay
tAS
tAH
tRR
tCW
tPD
MIN
0
50
40
110
Recovery at Power Up
VCC Slew Rate Power Down
VCC Slew Rate Power Up
CEI High to Power Fail
tREC
tF
tR
tPF
10
0
0
DS1234
(TA=25°C)
TYP
MAX
UNITS NOTES
5 pF
7 pF
(0°C to 70°C; VCCI = 5V ± 10%)
TYP
MAX
UNITS NOTES
ns
ns
ns
ns
20 ns
(0°C to 70°C; VCCI < VTP)
2 ms
µs
µs
ns
010692 5/7
5 Page | ||
| Páginas | Total 7 Páginas | |
| PDF Descargar | [ Datasheet DS1234.PDF ] | |
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