MAXIM DS1270W

DS1270W
3.3V 16Mb Nonvolatile SRAM
www.maxim-ic.com
FEATURES
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PIN ASSIGNMENT
Five years minimum data retention in the
absence of external power
Data is automatically protected during power
loss
Unlimited write cycles
Low-power CMOS operation
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 (IND) temperature range
of -40°C to +85°C
NC
A20
A18
A16
A14
A12
A7
A6
A5
A4
A3
36
35
34
33
32
31
30
29
28
27
26
25
VCC
A19
NC
A15
A17
WE
A13
A8
A9
A11
OE
A2
1
2
3
4
5
6
7
8
9
10
11
12
A1
13
24
CE
A0
DQ0
14
23
15
DQ7
DQ6
DQ1
16
22
21
DQ2
17
20
DQ4
GND
18
19
DQ3
A10
DQ5
36-Pin Encapsulated Package
740mil Extended
PIN DESCRIPTION
A0–A20
DQ0–DQ7
CE
WE
OE
VCC
GND
NC
- Address Inputs
- Data In/Data Out
- Chip Enable
- Write Enable
- Output Enable
- Power (+3.3V)
- Ground
- No Connect
DESCRIPTION
The DS1270W 16Mb nonvolatile (NV) SRAMs are 16,777,216-bit, fully static, NV SRAMs organized as
2,097,152 words by 8 bits. Each NV SRAM has a self-contained lithium energy source and control
circuitry that 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. There is no limit on the number of write cycles that can be executed, and no
additional support circuitry is required for microprocessor interfacing.
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110602
DS1270W
READ MODE
The DS1270 devices execute 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 21 address inputs
(A0–A20) defines which of the 2,097,152 bytes of data is 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 tACC.
WRITE MODE
The DS1270 devices execute a write cycle whenever 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 DS1270W provides full-functional capability for VCC greater than 3.0V and write protects by 2.8V.
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 2.5V, a power-switching circuit connects the lithium energy source to RAM to
retain data. During power-up, when VCC rises above approximately 2.5V, the power-switching circuit
connects external VCC to RAM and disconnects the lithium energy source. Normal RAM operation can
resume after VCC exceeds 3.0V.
FRESHNESS SEAL
Each DS1270 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 VTP, the lithium
energy source is enabled for battery backup operation.
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DS1270W
ABSOLUTE MAXIMUM RATINGS*
Voltage on Any Pin Relative to Ground
Operating Temperature Range
Storage Temperature Range
Soldering Temperature
*
-0.3V to +4.6V
0°C to 70°C (-40°C to +85°C for IND parts)
-40°C to +70°C (-40°C to +85°C for IND parts)
+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
(TA: See Note 10)
SYMBOL
MIN
TYP
MAX
UNITS
Power-Supply Voltage
VCC
3.0
3.3
3.6
V
Logic 1 Input Voltage
VIH
2.2
VCC
V
Logic 0 Input Voltage
VIL
0.0
+0.4
V
DC ELECTRICAL CHARACTERISTICS
PARAMETER
Input Leakage Current
(TA: See Note 10; VCC = 3.3V ± 0.3V)
SYMBOL
IIL
MIN
-4.0
I/O Leakage Current
IIO
-4.0
Output Current at 2.2V
IOH
-1.0
mA
Output Current at 0.4V
IOL
2.0
mA
TYP
MAX
+4.0
UNITS
+4.0
mA
ICCS1
150
300
mA
Standby Current CE = VCC - 0.2V
ICCS2
100
200
mA
Operating Current
ICCO1
50
mA
Write Protection Voltage
VTP
3.0
V
2.8
2.9
CAPACITANCE
NOTES
mA
Standby Current CE = 2.2V
PARAMETER
NOTES
(TA = +25°C)
SYMBOL
MIN
TYP
MAX
UNITS
Input Capacitance
CIN
20
40
pF
Input/Output Capacitance
CI/O
20
40
pF
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NOTES
DS1270W
(TA: See Note 10; VCC = 3.3V ± 0.3V)
AC ELECTRICAL CHARACTERISTICS
PARAMETER
Read Cycle Time
Access Time
SYMBOL
tRC
DS1270W-100
DS1270W-150
MIN
MIN
MAX
100
MAX
UNITS
ns
150
tACC
100
150
ns
NOTES
OE
to Output Valid
tOE
50
70
ns
CE
to Output Valid
tCO
100
150
ns
OE
or CE to Output Active
tCOE
Output High-Z from Deselection
tOD
Output Hold from Address Change
tOH
5
5
ns
Write Cycle Time
tWC
100
150
ns
Write Pulse Width
tWP
75
100
ns
Address Setup Time
tAW
0
0
ns
Write Recovery Time
tWR1
tWR2
5
20
5
20
ns
ns
12
13
Output High-Z from WE
tODW
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
ns
12
13
5
5
35
35
35
TIMING DIAGRAM: READ CYCLE
SEE NOTE 1
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35
ns
5
ns
5
3
DS1270W
TIMING DIAGRAM: WRITE CYCLE 1
TIMING DIAGRAM: WRITE CYCLE 2
SEE NOTES 2, 3, 4, 6, 7, 8 AND 13
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DS1270W
POWER-DOWN/POWER-UP CONDITION
SEE NOTE 11
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
ms
11
VCC Slew from VTP to 0V
tF
150
ms
VCC Slew from 0V to VTP
tR
150
ms
VCC Valid to CE and WE Inactive
tPU
2
ms
VCC Valid to End of Write Protection
tREC
125
ms
(TA = 25°C)
PARAMETER
Expected Data-Retention Time
SYMBOL
MIN
tDR
5
TYP
MAX
UNITS
NOTES
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. tDS is measured from the earlier of CE or WE going high.
5. These parameters are sampled with a 5pF 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 a 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.
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DS1270W
9. Each DS1270 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. DS1270 modules are recognized by Underwriters Laboratory (U.L.â) under file E99151.
DC TEST CONDITIONS
AC TEST CONDITIONS
Outputs Open
Cycle = 200ns for operating current
All voltages are referenced to ground
Output Load: 100pF + 1TTL Gate
Input Pulse Levels: 0 to 2.7V
Timing Measurement Reference Levels
Input: 1.5V
Output: 1.5V
Input Pulse Rise and Fall Times: 5ns
ORDERING INFORMATION
DS1270W - SSS - III
Operating Temperature Range
blank: 0°C to +70°C
IND: -40°C to +85°C
Access Speed
100: 100ns
150: 150ns
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DS1270W
DS1270W NONVOLATILE SRAM 36-PIN, 740MIL EXTENDED MODULE, LONG
PKG
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36-PIN
DIM
MIN
MAX
A IN.
MM
2.080
52.83
2.100
53.34
B IN.
MM
0.720
18.29
0.740
18.80
C IN.
MM
0.395
10.03
0.405
10.29
D IN.
MM
0.180
4.57
0.210
5.33
E IN.
MM
0.015
0.38
0.025
0.63
F IN.
MM
0.120
3.05
0.150
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