M48T08
M48T08Y, M48T18
5V, 64 Kbit (8 Kb x8) TIMEKEEPER
®
SRAM
FEATURES SUMMARY
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■
■
■
■
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INTEGRATED ULTRA LOW POWER SRAM,
REAL TIME CLOCK, POWER-FAIL
CONTROL CIRCUIT, AND BATTERY
BYTEWIDE™ RAM-LIKE CLOCK ACCESS
BCD CODED YEAR, MONTH, DAY, DATE,
HOURS, MINUTES, and SECONDS
TYPICAL CLOCK ACCURACY OF ±1
MINUTE A MONTH, AT 25°C
AUTOMATIC POWER-FAIL CHIP
DESELECT AND WRITE PROTECTION
WRITE PROTECT VOLTAGES
(V
PFD
= Power-fail Deselect Voltage):
– M48T08: V
CC
= 4.75 to 5.5V
4.5V
≤
V
PFD
≤
4.75V
– M48T18/T08Y: V
CC
= 4.5 to 5.5V
4.2V
≤
V
PFD
≤
4.5V
SOFTWARE CONTROLLED CLOCK
CALIBRATION FOR HIGH ACCURACY
APPLICATIONS
SELF-CONTAINED BATTERY AND
CRYSTAL IN THE CAPHAT™ DIP
PACKAGE
PACKAGING INCLUDES A 28-LEAD SOIC
AND SNAPHAT
®
TOP (to be ordered
separately)
SOIC PACKAGE PROVIDES DIRECT
CONNECTION FOR A SNAPHAT TOP
WHICH CONTAINS THE BATTERY AND
CRYSTAL
PIN AND FUNCTION COMPATIBLE WITH
DS1643 and JEDEC STANDARD 8K x8
SRAMs
RoHS COMPLIANCE
Lead-free components are compliant with the
RoHS Directive.
Figure 1. 28-pin PCDIP, CAPHAT™ Package
28
1
PCDIP28 (PC)
Battery/Crystal
CAPHAT
Figure 2. 28-pin SOIC Package
SNAPHAT (SH)
Battery/Crystal
28
1
SOH28 (MH)
Rev 7.0
December 2005
1/27
M48T08, M48T08Y, M48T18
TABLE OF CONTENTS
FEATURES SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Figure 1. 28-pin PCDIP, CAPHAT™ Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Figure 2. 28-pin SOIC Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
SUMMARY DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Figure 3.
Table 1.
Figure 4.
Figure 5.
Figure 6.
Logic Diagram . . . . . . . . . . . . . . . . . . . . .
Signal Names . . . . . . . . . . . . . . . . . . . . .
DIP Connections . . . . . . . . . . . . . . . . . . .
SOIC Connections . . . . . . . . . . . . . . . . . .
Block Diagram . . . . . . . . . . . . . . . . . . . . .
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.....4
.....4
.....5
.....5
.....5
OPERATION MODES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Table 2. Operating Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
READ Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Figure 7. READ Mode AC Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Table 3. READ Mode AC Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
WRITE Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Figure 8. WRITE Enable Controlled, WRITE AC Waveform. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Figure 9. Chip Enable Controlled, WRITE AC Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Table 4. WRITE Mode AC Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Data Retention Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Power-fail Interrupt Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
CLOCK OPERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Reading the Clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Setting the Clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Table 5. Register Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Stopping and Starting the Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Calibrating the Clock. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Figure 10.Crystal Accuracy Across Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Figure 11.Clock Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
V
CC
Noise And Negative Going Transients. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Figure 12.Supply Voltage Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
MAXIMUM RATING. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Table 6. Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
DC AND AC PARAMETERS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Table 7. Operating and AC Measurement Conditions . . . . . . . . . . . . . . . . . . . . . . . .
Figure 13.AC Testing Load Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table 8. Capacitance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table 9. DC Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 14.Power Down/Up Mode AC Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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. . . . 18
. . . . 18
. . . . 18
. . . . 19
. . . . 20
2/27
M48T08, M48T08Y, M48T18
Table 10. Power Down/Up AC Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Table 11. Power Down/Up Trip Points DC Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
PACKAGE MECHANICAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Figure 15.PCDIP28 – 28-pin Plastic DIP, battery CAPHAT, Package Outline . . . . . . . . . . . . . . . . 21
Table 12. PCDIP28 – 28-pin Plastic DIP, battery CAPHAT, Package Mechanical Data. . . . . . . . . 21
Figure 16.SOH28 – 28-lead Plastic Small Outline, 4-socket battery SNAPHAT, Package Outline. 22
Table 13. SOH28 – 28-lead Plastic SO, 4-socket battery SNAPHAT, Package Mech. Data . . . . . 22
Figure 17.SH – 4-pin SNAPHAT Housing for 48mAh Battery & Crystal, Package Outline . . . . . . . 23
Table 14. SH – 4-pin SNAPHAT Housing for 48mAh Battery & Crystal, Package Mech. Data. . . . 23
Figure 18.SH – 4-pin SNAPHAT Housing for 120mAh Battery & Crystal, Package Outline . . . . . . 24
Table 15. SH – 4-pin SNAPHAT Housing for 120mAh Battery & Crystal, Package Mech. Data. . . 24
PART NUMBERING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Table 16. Ordering Information Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Table 17. SNAPHAT Battery Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
REVISION HISTORY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Table 18. Document Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3/27
M48T08, M48T08Y, M48T18
SUMMARY DESCRIPTION
The M48T08/18/08Y TIMEKEEPER
®
RAM is an
8K x 8 non-volatile static RAM and real time clock
which is pin and functional compatible with the
DS1643. The monolithic chip is available in two
special packages to provide a highly integrated
battery backed-up memory and real time clock so-
lution.
The M48T08/18/08Y is a non-volatile pin and func-
tion equivalent to any JEDEC standard 8K x 8
SRAM. It also easily fits into many ROM, EPROM,
and EEPROM sockets, providing the non-volatility
of PROMs without any requirement for special
WRITE timing or limitations on the number of
WRITEs that can be performed.
The 28-pin, 600mil DIP CAPHAT™ houses the
M48T08/18/08Y silicon with a quartz crystal and a
long- life lithium button cell in a single package.
The 28-pin, 330mil SOIC provides sockets with
gold plated contacts at both ends for direct con-
nection to a separate SNAPHAT
®
housing con-
taining the battery and crystal. The unique design
allows the SNAPHAT battery package to be
mounted on top of the SOIC package after the
completion of the surface mount process. Inser-
tion of the SNAPHAT housing after reflow pre-
vents potential battery and crystal damage due to
the high temperatures required for device surface-
mounting. The SNAPHAT housing is keyed to pre-
vent reverse insertion.
The SOIC and battery/crystal packages are
shipped separately in plastic anti-static tubes or in
Tape & Reel form. For the 28 lead SOIC, the bat-
tery/crystal package (e.g., SNAPHAT) part num-
ber is “M4T28-BR12SH” or “M4T32-BR12SH”
(see
Table 17., page 25).
Table 1. Signal Names
A0-A12
DQ0-DQ7
Address Inputs
Data Inputs / Outputs
Power Fail Interrupt (Open Drain)
Chip Enable 1
Chip Enable 2
Output Enable
WRITE Enable
Supply Voltage
Ground
Figure 3. Logic Diagram
VCC
13
A0-A12
8
DQ0-DQ7
INT
E1
E2
W
E1
E2
M48T08
M48T08Y
M48T18
INT
G
W
V
CC
G
V
SS
VSS
AI01020
4/27
M48T08, M48T08Y, M48T18
Figure 4. DIP Connections
INT
A12
A7
A6
A5
A4
A3
A2
A1
A0
DQ0
DQ1
DQ2
VSS
1
28
2
27
3
26
4
25
5
24
6
23
7
M48T08 22
8
M48T18 21
9
20
10
19
11
18
12
17
13
16
14
15
AI01182
Figure 5. SOIC Connections
VCC
W
E2
A8
A9
A11
G
A10
E1
DQ7
DQ6
DQ5
DQ4
DQ3
INT
A12
A7
A6
A5
A4
A3
A2
A1
A0
DQ0
DQ1
DQ2
VSS
28
1
2
27
3
26
4
25
5
24
6
23
7
22
M48T08Y
8
21
9
20
10
19
11
18
12
17
13
16
14
15
AI01021B
VCC
W
E2
A8
A9
A11
G
A10
E1
DQ7
DQ6
DQ5
DQ4
DQ3
Figure 6. Block Diagram
OSCILLATOR AND
CLOCK CHAIN
32,768 Hz
CRYSTAL
POWER
8 x 8 BiPORT
SRAM ARRAY
A0-A12
8184 x 8
SRAM ARRAY
LITHIUM
CELL
VOLTAGE SENSE
AND
SWITCHING
CIRCUITRY
VPFD
DQ0-DQ7
E1
E2
W
G
VCC
INT
VSS
AI01333
5/27
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