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FEATURES
§ 10 years minimum data retention in the
absence of external power
§ Data is automatically protected during power
loss
§ Replaces 128k x 8 volatile static RAM,
EEPROM or Flash memory
§ Unlimited write cycles
§ Low-power CMOS
§ Read and write access times as fast as 100ns
§ Lithium energy source is electrically
disconnected to retain freshness until power is
applied for the first time
§ Optional industrial temperature range of
-40°C to +85°C, designated IND
§ JEDEC standard 32-pin DIP package
§ PowerCap Module (PCM) package
- Directly surface-mountable module
- Replaceable snap-on PowerCap provides
lithium backup battery
- Standardized pinout for all nonvolatile
SRAM products
- Detachment feature on PowerCap allows
easy removal using a regular screwdriver
PIN ASSIGNMENT
PIN DESCRIPTION
A0 - A16 - Address Inputs
DQ0 - DQ7 - Data In/Data Out
CE - Chip Enable
WE - Write Enable
OE - Output Enable
VCC - Power (+3.3V)
GND - Ground
NC - No Connect
DS1245W
3.3V 1024k Nonvolatile SRAM
www.maxim-ic.com
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4
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31
32-PIN Encapsulated Package
740-Mil Extended
A14
A7
A5
A4
A3
A2
A1
A0
DQ1
DQ0
V
CC
A
15
NC
WE
A
13
A
8
A
9
A
11
OE
A
10
CE
DQ7
DQ5
DQ6
32
30
29
28
27
26
25
24
23
22
21
19
20
A16
A12
A6
NC
DQ2
GND
15
16
18
17
DQ4
DQ3
1
NC 2
3
A15
A16
NC
VCC
WE
OE
CE
DQ7
DQ6
DQ5
DQ4
DQ3
DQ2
DQ1
DQ0
GND
4
5
6
7
8
9
10
11
12
13
14
15
16
17
NC
A
14
33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
A
13
A
12
A
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A
10
A
9
A
8
A
7
A
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A
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A
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A
3
A
2
A
1
A
0
34 NC
GND VBAT
34-Pin PowerCap Module (PCM)
(Uses DS9034PC PowerCap)
DS1245W
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DESCRIPTION
The DS1245W 3.3V 1024k Nonvolatile SRAM is a 1,048,576-bit, fully static, nonvolatile SRAM
organized as 131,072 words by 8 bits. Each NV SRAM has a self-contained lithium energy source and
control circuitry which constantly monitors VCC for an out-of-tolerance condition. When such a condition
occurs, the lithium energy source is automatically switched on and write protection is unconditionally
enabled to prevent data corruption. DIP-package DS1245W devices can be used in place of existing 128k
x 8 static RAMs directly conforming to the popular bytewide 32-pin DIP standard. DS1245W devices in
the PowerCap Module package are directly surface mountable and are normally paired with a DS9034PC
PowerCap to form a complete Nonvolatile SRAM module. There is no limit on the number of write
cycles that can be executed and no additional support circuitry is required for microprocessor interfacing.
READ MODE
The DS1245W executes a read cycle whenever WE (Write Enable) is inactive (high) and CE (Chip
Enable) and OE (Output Enable) are active (low). The unique address specified by the 17 address inputs
(A0 - A16) defines which of the 131,072 bytes of data is to be accessed. Valid data will be available to the
eight data output drivers within tACC (Access Time) after the last address input signal is stable, providing
that CE and OE (Output Enable) access times are also satisfied. If OE and CE access times are not
satisfied, then data access must be measured from the later occurring signal ( CE or OE ) and the limiting
parameter is either tCO for CE or tOE for OE rather than address access.
WRITE MODE
The DS1245W executes a write cycle whenever the WE and CE signals are active (low) after address
inputs are stable. The later occurring falling edge of CE or WE will determine the start of the write cycle.
The write cycle is terminated by the earlier rising edge of CE or WE . All address inputs must be kept
valid throughout the write cycle. WE must return to the high state for a minimum recovery time (tWR)
before another cycle can be initiated. The OE control signal should be kept inactive (high) during write
cycles to avoid bus contention. However, if the output drivers are enabled ( CE and OE active) then WE
will disable the outputs in tODW from its falling edge.
DATA RETENTION MODE
The DS1245W provides full functional capability for VCC greater than 3.0 volts and write protects by 2.8
volts. Data is maintained in the absence of VCC without any additional support circuitry. The nonvolatile
static RAMs constantly monitor VCC. Should the supply voltage decay, the NV SRAMs automatically
write protect themselves, all inputs become “don’t care,” and all outputs become high impedance. As VCC
falls below approximately 3.0 volts, a power switching circuit connects the lithium energy source to
RAM to retain data. During power-up, when VCC rises above approximately 2.5 volts, the power
switching circuit connects external VCC to RAM and disconnects the lithium energy source. Normal
RAM operation can resume after VCC exceeds 3.0 volts.
FRESHNESS SEAL
Each DS1245W device is shipped from Dallas Semiconductor with its lithium energy source
disconnected, guaranteeing full energy capacity. When VCC is first applied at a level greater than 3.0
volts, the lithium energy source is enabled for battery back-up operation.
PACKAGES
The DS1245W is available in two packages: 32-pin DIP and 34-pin PowerCap Module (PCM). The 32-
pin DIP integrates a lithium battery, an SRAM memory and a nonvolatile control function into a single
package with a JEDEC-standard 600-mil DIP pinout. The 34-pin PowerCap Module integrates SRAM
DS1245W
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memory and nonvolatile control into a module base along with contacts for connection to the lithium
battery in the DS9034PC PowerCap. The PowerCap Module package design allows a DS1245W PCM
device to be surface mounted without subjecting its lithium backup battery to destructive high-
temperature reflow soldering. After a DS1245W module base is reflow soldered, a DS9034PC PowerCap
is snapped on top of the base to form a complete Nonvolatile SRAM module. The DS9034PC is keyed to
prevent improper attachment. DS1245W module bases and DS9034PC PowerCaps are ordered separately
and shipped in separate containers. See the DS9034PC data sheet for further information.
ABSOLUTE MAXIMUM RATINGS*
Voltage on Any Pin Relative to Ground -0.3V to +4.6V
Operating Temperature 0°C to 70°C, -40°C to +85°C for Ind parts
Storage Temperature -40°C to +70°C, -40°C to +85°C for Ind parts
Soldering Temperature 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 (tA: See Note 10)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Power Supply Voltage VCC 3.0 3.3 3.6 V
Logic 1 VIH 2.2 VCC V
Logic 0 VIL 0.0 0.4 V
DC ELECTRICAL CHARACTERISTICS (tA: See Note 10) (VCC=3.3V ± 0.3V)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Input Leakage Current IIL -1.0 +1.0 mA
I/O Leakage Current CE ³ VIH £ VCC IIO -1.0 +1.0 mA
Output Current @ 2.2V IOH -1.0 mA
Output Current @ 0.4V IOL 2.0 mA
Standby Current CE =2.2V ICCS1 50 250 mA
Standby Current CE =VCC-0.2V ICCS2 30 150 mA
Operating Current ICCO1 50 mA
Write Protection Voltage VTP 2.8 2.9 3.0 V
CAPACITANCE (tA=25°C)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Input Capacitance CIN 510pF
Input/Output Capacitance CI/O 510pF
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AC ELECTRICAL CHARACTERISTICS (tA: See Note 10) (VCC=3.3V ± 0.3V)
DS1245W-100 DS1245W-150
PARAMETER SYMBOL
MIN MAX MIN MAX
UNITS NOTES
Read Cycle Time tRC 100 150 ns
Access Time tACC 100 150 ns
OE to Output Valid tOE 50 70 ns
CE to Output Valid tCO 100 150 ns
OE or CE to Output Active tCOE 5 5 ns 5
Output High Z from Deselection tOD 35 35 ns 5
Output Hold from Address Change tOH 55ns
Write Cycle Time tWC 100 150 ns
Write Pulse Width tWP 75 100 ns 3
Address Setup Time tAW 00ns
Write Recovery Time tWR1
tWR2
5
20
5
20
ns 12
13
Output High Z from WE tODW 35 35 ns 5
Output Active from WE tOEW 5 5 ns 5
Data Setup Time tDS 40 60 ns 4
Data Hold Time tDH1
tDH2
0
20
0
20
ns 12
13
READ CYCLE
DS1245W
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WRITE CYCLE 1
\SEE NOTES 2, 3, 4, 6, 7, 8 AND 12
DS1245W
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WRITE CYCLE 2
\SEE NOTES 2, 3, 4, 6, 7, 8 AND 12
POWER-DOWN/POWER-UP CONDITION
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POWER-DOWN/POWER-UP TIMING (tA: See Note 10)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
VCC Fail Detect to CE and WE Inactive tPD 1.5 ms11
VCC slew from VTP to 0V tF150 15 ms
VCC slew from 0V to VTP tR150 ms
VCC Valid to CE and WE Inactive tPU 2ms
VCC Valid to End of Write Protection tREC 125 ms
(tA=25°C)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Expected Data Retention Time tDR 10 years 9
WARNING:
Under no circumstance are negative undershoots, of any amplitude, allowed when device is in battery
backup mode.
NOTES:
1. WE is high for a Read Cycle.
2. OE = VIH or VIL. If OE = VIH during write cycle, the output buffers remain in a high impedance state.
3. tWP is specified as the logical AND of CE and WE . tWP is measured from the latter of CE or WE
going low to the earlier of CE or WE going high.
4. tDH, tDS are measured from the earlier of CE or WE going high.
5. These parameters are sampled with a 5 pF load and are not 100% tested.
6. If the CE low transition occurs simultaneously with or latter than the WE low transition, the output
buffers remain in a high impedance state during this period.
7. If the CE high transition occurs prior to or simultaneously with the WE high transition, the output
buffers remain in high impedance state during this period.
8. If WE is low or the WE low transition occurs prior to or simultaneously with the CE low transition,
the output buffers remain in a high impedance state during this period.
9. Each DS1245W has a built-in switch that disconnects the lithium source until VCC is first applied by
the user. The expected tDR is defined as accumulative time in the absence of VCC starting from the
time power is first applied by the user.
10. All AC and DC electrical characteristics are valid over the full operating temperature range. For
commercial products, this range is 0°C to 70°C. For industrial products (IND), this range is -40°C to
+85°C.
11. In a power-down condition the voltage on any pin may not exceed the voltage on VCC.
12. tWR1 and tDH1 are measured from WE going high.
13. tWR2 and tDH2 are measured from CE going high.
14. DS1245 modules are recognized by Underwriters Laboratory (U.L.®) under file E99151.
DS1245W
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DC TEST CONDITIONS AC TEST CONDITIONS
Outputs Open Output Load: 100 pF + 1TTL Gate
Cycle = 200ns for operating current Input Pulse Levels: 0 to 2.7V
All voltages are referenced to ground Timing Measurement Reference Levels
Input: 1.5V
Output: 1.5V
Input pulse Rise and Fall Times: 5ns
ORDERING INFORMATION
DS1245 W P - SSS - III
Operating Temperature Range
blank: 0° to 70°C
IND: -40° to +85°C
Access Speed
100: 100ns
150: 150ns
Package Type
blank: 32-pin 600-mil DIP
P: 34-pin PowerCap Module
DS1245W NONVOLATILE SRAM, 32-PIN 740-MIL EXTENDED DIP MODULE
PKG 32-PIN
DIM MIN MAX
A IN.
MM
1.680
42.67
1.700
43.18
B IN.
MM
0.720
18.29
0.740
18.80
C IN.
MM
0.355
9.02
0.375
9.52
D IN.
MM
0.080
2.03
0.110
2.79
E IN.
MM
0.015
0.38
0.025
0.63
F IN.
MM
0.120
3.05
0.160
4.06
G IN.
MM
0.090
2.29
0.110
2.79
H IN.
MM
0.590
14.99
0.630
16.00
J IN.
MM
0.008
0.20
0.012
0.30
K IN.
MM
0.015
0.38
0.021
0.53
DS1245W
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DS1245W NONVOLATILE SRAM, 34-PIN POWERCAP MODULE
INCHES
PKG
DIM MIN NOM MAX
A0.920 0.925 0.930
B0.980 0.985 0.990
C- - 0.080
D0.052 0.055 0.058
E0.048 0.050 0.052
F0.015 0.020 0.025
G0.020 0.025 0.030
DS1245W
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DS1245W NONVOLATILE SRAM, 34-PIN POWERCAP MODULE WITH
POWERCAP
INCHES
PKG
DIM MIN NOM MAX
A0.920 0.925 0.930
B0.955 0.960 0.965
C0.240 0.245 0.250
D0.052 0.055 0.058
E0.048 0.050 0.052
F0.015 0.020 0.025
G0.020 0.025 0.030
ASSEMBLY AND USE
Reflow soldering
Dallas Semiconductor recommends that PowerCap Module bases experience one pass through solder
reflow oriented label-side up (live-bug).
Hand soldering and touch-up
Do not touch soldering iron to leads for more than 3 seconds. To solder, apply flux to the pad, heat the
lead frame pad and apply solder. To remove part, apply flux, heat pad until solder reflows, and use a
solder wick.
LPM replacement in a socket
To replace a Low Profile Module in a 68-pin PLCC socket, attach a DS9034PC PowerCap to a module
base then insert the complete module into the socket one row of leads at a time, pushing only on the
corners of the cap. Never apply force to the center of the device. To remove from a socket, use a PLCC
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extraction tool and ensure that it does not hit or damage any of the module IC components. Do not use
any other tool for extraction.
RECOMMENDED POWERCAP MODULE LAND PATTERN
INCHES
PKG
DIM MIN NOM MAX
A- 1.050 -
B- 0.826 -
C- 0.050 -
D- 0.030 -
E- 0.112 -
RECOMMENDED POWERCAP MODULE SOLDER STENCIL
INCHES
PKG
DIM MIN NOM MAX
A- 1.050 -
B- 0.890 -
C- 0.050 -
D- 0.030 -
E- 0.080 -
