1213B.PDF

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DS1213B
SmartSocket 16k/64k
www.dalsemi.com
FEATURES
Accepts standard 2K x 8 or 8K x 8 CMOS
static RAMs
Embedded lithium energy cell retains RAM
data
Self-contained circuitry safeguards data
Data retention time is greater than 10 years
with proper RAM selection
IC socket permits upgrading from 2K x 8 to
8K RAM
Proven gas-tight socket contacts
Operating temperature range 0°C to 70°C
PIN ASSIGNMENT
1
2
3
4
5
6
7
8
9
10
11
12
13
GND 14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
V
CC
V
CC
CE
28-Pin Intelligent Socket
PIN DESCRIPTION
- Conditioned Chip Enable
V
CC
- Switched V
CC
GND
- Ground
All pins pass through except 20, 26 and 28.
CE
DESCRIPTION
The DS1213B SmartSocket is a 28-pin, 600 mil DIP socket with a built-in CMOS controller circuit and
an embedded lithium energy source. It accepts either 24-pin 2K x 8 (lower-justified) or 28-pin 8K x 8
JEDEC bytewide CMOS static RAM. When the socket is mated with a CMOS RAM, it provides a
complete solution to problems associated with memory volatility. The Smart-Socket monitors incoming
V
CC
for an out-of-tolerance condition. When such a condition occurs, the internal lithium energy source is
automatically switched on and write protection is unconditionally enabled to prevent data corruption.
Using the SmartSocket saves printed circuit board space since the SRAM/SmartSocket combination
occupies no more area than the SRAM alone. The SmartSocket modifies only pins 20, 26 and 28, to
nonvolatize the RAM. All other pins are passed straight through.
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022900
DS1213B
OPERATION
The DS1213B SmartSocket performs five circuit functions required to battery back up a CMOS memory.
The first function involves switching between the battery and the V
CC
supply, depending on which is
greater. The switch has a voltage drop of less than 0.2 volts.
The second function is power-fail detection. The DS1213B constantly monitors the V
CC
supply. When
V
CC
falls below 4.75 volts, a precision comparator detects the condition and inhibits the RAM chip
enable.
The third function, write protection, is accomplished by holding the RAM chip enable signal to within 0.2
volts of V
CC
or the battery supply whichever is greater. If the incoming chip enable signal is active at the
time power fail detection occurs, write protection is delayed until after the current memory cycle is
complete to avoid corruption of data. Power fail detection occurs in the range of 4.75 to 4.5 volts. During
nominal power supply conditions the chip enable signal will be passed through from the socket pin to the
socket contact with a maximum propagation delay of 20 ns.
The fourth function the DS1213B performs is to check battery status to warn of potential data loss. Each
time that V
CC
power is restored to the SmartSocket the battery voltage is checked with a precision
comparator. If the battery supply is less than 2.0 volts, the second memory access to the SmartSocket is
inhibited. Battery status can, therefore, be determined by a three-step process. First, a read cycle is
performed to any location in the memory, in order to save the contents of that location. A subsequent
write cycle can then be executed to the same memory location, altering the data. If the next read cycle
fails to verify the written data, then the battery voltage is less than 2.0V and data is in danger of being
corrupted.
The fifth function the SmartSocket provides is battery redundancy. In many applications, data integrity is
paramount. In these applications it is desirable to use two batteries to ensure reliability. The DS1213B
SmartSocket provides two batteries and an internal isolation switch to select between them. During
battery back up, the battery with the highest voltage is selected for use. If one battery fails, the other
automatically takes over. The switch between batteries is transparent to the user. A battery status warning
will occur if both batteries are less than 2.0 volts. Each of the two internal lithium cells has a 45 mAh
capacity.
NOTE:
As shipped from Dallas Semiconductor, battery voltage cannot be measured on the V
CC
socket contact.
Only after V
CC
has been applied to the device for the first time and then removed will the battery voltage
be present on socket contacts 28, 26 and 20.
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DS1213B
ABSOLUTE MAXIMUM RATINGS*
Voltage on Any Pin Relative to Ground
Operating Temperature
Storage Temperature
Soldering Temperature
-0.3V to +7.0V
0°C to 70°C
-40°C to +70°C
260°C for 10 seconds
∗
This is a stress rating only and functional operation of the device at these or any other conditions
above those indicated in the operation sections of this specification is not implied. Exposure to
absolute maximum rating conditions for extended periods of time may affect reliability.
RECOMMENDED DC OPERATING CONDITIONS
PARAMETER
PIN 26 L, PIN 28 L
Supply Voltage
Logic 1 PIN 20 L
Logic 0 PIN 20 L
SYMBOL
V
CC
V
IH
V
IL
MIN
4.75
2.2
-0.3
TYP
5.0
MAX
5.5
V
CC
+0.3
+0.8
(0°C to 70°C)
°
°
UNITS
V
V
V
NOTES
1,3
1,3
1,3
DC ELECTRICAL CHARACTERISTICS
PARAMETER
PIN 26 L, PIN 28 L
Supply Current
PIN 26 U, PIN 28 U
Supply Voltage
PIN 26 U, PIN 28 U
Supply Current
PIN 20 L
CE
Input Leakage
PIN 20 U
CE
Output @ 2.4V
PIN 20 U
CE
Output @ 4V
SYMBOL
I
CC
V
CCO
I
CCO
I
IL
I
OH
I
OL
-1.0
-1.0
MIN
(0°C to 70°C; V
CC
= 4.75 to 5.5V)
°
°
TYP
MAX
5
UNITS
mA
V
80
+1.0
4.0
mA
µA
mA
mA
NOTES
3,4,5
1,3,8
3,8
3,4
2,3
2,3
V
CC
-0.2
DC ELECTRICAL CHARACTERISTICS
PARAMETER
PIN 20 Output
PIN 26 U, PIN 28 U
Battery Current
PIN 26 U, PIN 28 U
Battery Voltage
SYMBOL
V
OHL
I
BAT
V
BAT
2
3
MIN
V
CC
-0.2
V
BAT-
0.2
TYP
(0°C to 70°C; V
CC
< 4.5V)
°
°
MAX
UNITS
V
µA
V
NOTES
1,3
3,6
1,3
1
3.6
CAPACITANCE
PARAMETER
Input Capacitance PIN 20 L
Output Capacitance PIN 20 U
SYMBOL
C
IN
C
OUT
MIN
TYP
MAX
5
7
UNITS
pF
pF
(T
A
= 25°C)
°
NOTES
3
3
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DS1213B
AC ELECTRICAL CHARACTERISTICS
PARAMETER
CE
Propagation Delay
CE
High to Power Fall
SYMBOL
t
PF
t
PD
MIN
5
(0°C to 70°C; V
CC
= 4.75 to 5.5V)
°
°
TYP
10
MAX
20
0
UNITS
ns
ns
NOTES
2,9
AC ELECTRICAL CHARACTERISTICS
PARAMETER
Recovery at Power -Up
VCC Slew Rate 4.75 - 4.5 V
VCC Slew Rate 4.5-3 V
VCC Slew Rate 4.5-4.75 V
CE
Pulse Width
SYMBOL
t
REC
t
F
t
FB
t
R
t
CE
MIN
2
300
10
0
TYP
80
(0°C to 70°C; V
CCI
< 4.75 V)
°
°
MAX
125
UNITS
µs
µs
µs
µs
µs
NOTES
1.5
7
TIMING DIAGRAM: POWER-DOWN
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DS1213B
TIMING DIAGRAM: POWER-UP
WARNINGS:
Under no circumstances are negative undershoots, of any amplitude, allowed when device is in battery
backup mode.
Water washing for flux removal will discharge internal lithium source because exposed voltage pins
are present.
NOTES:
1. All voltages are referenced to ground.
2. Measured with a load as shown in Figure 1.
3. Pin locations are designated “U” (for upper) when a parameter definition refers to the socket
receptacle and “L” (for lower) when a parameter definition refers to the socket pin.
4. No memory inserted in the socket.
5. Pin 26 L may be connected to V
CC
or left disconnected at the PC board.
6. I
BAT
is the maximum load current which a correctly installed memory can use in the data retention
mode and meet data retention expectations of more than 10 years at 25°C.
7. t
CE
max. must be met to ensure data integrity on power loss.
8. V
CC
is within nominal limits and a memory is installed in the socket.
9. Input pulse rise and fall times equal 10 ns.
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