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TI-BQ4017.pdf
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TI-BQ4017.pdf
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Features
➤
Data retention in the absence of
power
➤
Automatic write-protection dur
-
ing power-up/power-down cycles
➤
Conventional SRAM operation;
unlimited write cycles
➤
5-year minimum data retention
in absence of power
➤
Battery internally isolated until
power is applied
General Description
The CMOS bq4017 is a nonvolatile
16,777,216-bit static RAM organized
as 2,097,152 words by 8 bits. The
integral control circuitry and lith
-
ium energy source provide reliable
nonvolatility coupled with the un
-
limited write cycles of standard
SRAM.
The control circuitry constantly
monitors the single 5V supply for an
out-of-tolerance condition. When V
CC
falls out of tolerance, the SRAM is
unconditionally write-protected to
prevent an inadvertent write opera
-
tion.
At this time the integral energy
source is switched on to sustain the
memory until after V
CC
returns valid.
The bq4017 uses extremely low
standby current CMOS SRAMs, cou
-
pled with small lithium coin cells to
provide nonvolatility without long
write-cycle times and the write-cycle
limitations associated with EE
-
PROM.
The bq4017 has the same interface
as industry-standard SRAMs and
requires no external circuitry.
1
Selection Guide
Part
Number
Maximum
Access
Time (ns)
Negative
Supply
Tolerance
Part
Number
Maximum
Access
Time (ns)
Negative
Supply
Tolerance
bq4017MC -70 70 -5% bq4017YMC -70 70 -10%
1
PN401701.eps
36-Pin DIP Module
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
NC
A
20
A
18
A
16
A
14
A
12
A
7
A
6
A
5
A
4
A
3
A
2
A
1
A
0
DQ
1
DQ
2
V
SS
DQ
0
V
CC
A
19
NC
A
15
A
17
WE
A
13
A
8
A
9
A
11
OE
A
10
CE
DQ
7
DQ
5
DQ
4
DQ
3
DQ
6
Pin Names
A
0
–A
20
Address inputs
DQ
0
–DQ
7
Data input/output
CE
Chip enable input
OE
Output enable input
WE
Write enable input
V
CC
Supply voltage input
V
SS
Ground
NC No connect
Block Diagram
bq4017/bq4017Y
5/95
Pin Connections
2048Kx8 Nonvolatile SRAM
Functional Description
When power is valid, the bq4017 operates as a standard
CMOS SRAM. During power-down and power-up cycles,
the bq4017 acts as a nonvolatile memory, automatically
protecting and preserving the memory contents.
Power-down/power-up control circuitry constantly moni
-
tors the V
CC
supply for a power-fail-detect threshold
V
PFD
. The bq4017 monitors for V
PFD
= 4.62V typical for
use in systems with 5% supply tolerance. The bq4017Y
monitors for V
PFD
= 4.37V typical for use in systems
with 10% supply tolerance.
When V
CC
falls below the V
PFD
threshold, the SRAM
automatically write-protects the data. All outputs be
-
come high impedance, and all inputs are treated as
“don’t care.” If a valid access is in process at the time of
power-fail detection, the memory cycle continues to com
-
pletion. If the memory cycle fails to terminate within
time t
WPT
, write-protection takes place.
As V
CC
falls past V
PFD
and approaches 3V, the control
circuitry switches to the internal lithium backup supply,
which provides data retention until valid V
CC
is applied.
When V
CC
returns to a level above the internal backup
cell voltage, the supply is switched back to V
CC
. After
V
CC
ramps above the V
PFD
threshold, write-protection
continues for a time t
CER
(120ms maximum) to allow for
processor stabilization. Normal memory operation may
resume after this time.
The internal coin cells used by the bq4017 have an ex
-
tremely long shelf life. The bq4017 provides data reten
-
tion for more than 5 years in the absence of system
power.
As shipped from Unitrode, the integral lithium cells are
electrically isolated from the memory. (Self-discharge in
this condition is approximately 0.5% per year.) Follow
-
ing the first application of V
CC
, this isolation is broken,
and the lithium backup provides data retention on sub
-
sequent power-downs.
2
Truth Table
Mode CE WE OE I/O Operation Power
Not selected H X X High Z Standby
Output disable L H H High Z Active
Read L H L D
OUT
Active
Write L L X D
IN
Active
Absolute Maximum Ratings
Symbol Parameter Value Unit Conditions
V
CC
DC voltage applied on V
CC
relative to V
SS
-0.3 to 7.0 V
V
T
DC voltage applied on any pin excluding V
CC
relative to V
SS
-0.3 to 7.0 V
V
T
≤
V
CC
+ 0.3
T
OPR
Operating temperature 0 to +70 °C
T
STG
Storage temperature -40 to +70 °C
T
BIAS
Temperature under bias -10 to +70 °C
T
SOLDER
Soldering temperature +260 °C For 10 seconds
Note: Permanent device damage may occur if Absolute Maximum Ratings are exceeded. Functional operation
should be limited to the Recommended DC Operating Conditions detailed in this data sheet. Exposure to con
-
ditions beyond the operational limits for extended periods of time may affect device reliability.
bq4017/bq4017Y
3
Recommended DC Operating Conditions (T
A
= 0 to 70°C)
Symbol Parameter Minimum Typical Maximum Unit Notes
V
CC
Supply voltage
4.5 5.0 5.5 V bq4017Y
4.75 5.0 5.5 V bq4017
V
SS
Supply voltage 0 0 0 V
V
IL
Input low voltage -0.3 - 0.8 V
V
IH
Input high voltage 2.2 - V
CC
+ 0.3 V
Note: Typical values indicate operation at T
A
= 25°C.
DC Electrical Characteristics (T
A
= 0 to 70°C, V
CCmin
≤
V
CC
≤
V
CCmax
)
Symbol Parameter Minimum Typical Maximum Unit Conditions/Notes
I
LI
Input leakage current - -
±
4
µ
AV
IN
= V
SS
to V
CC
I
LO
Output leakage current - -
±
4
µ
A
CE
= V
IH
or OE = V
IH
or
WE
= V
IL
V
OH
Output high voltage 2.4 - - V I
OH
= -1.0 mA
V
OL
Output low voltage - - 0.4 V I
OL
= 2.1 mA
I
SB1
Standby supply current - 7 17 mA CE = V
IH
I
SB2
Standby supply current - 2.5 5 mA
0V
≤
V
IN
≤
0.2V,
CE
≥
V
CC
- 0.2V,
or V
IN
≥
V
CC
- 0.2
I
CC
Operating supply current - 75 115 mA
Min. cycle, duty = 100%,
CE
= V
IL
,I
I/O
= 0mA,
A19 < V
IL
or A19 > V
IH
,
A20 < V
IL
or A20 > V
IH
V
PFD
Power-fail-detect voltage
4.55 4.62 4.75 V bq4017
4.30 4.37 4.50 V bq4017Y
V
SO
Supply switch-over voltage - 3 - V
Note: Typical values indicate operation at T
A
= 25°C, V
CC
= 5V.
bq4017/bq4017Y
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