STMICROELECTRONICS M48T08

M48T08
M48T08Y, M48T18
5V, 64Kbit (8 Kb x 8) TIMEKEEPER® SRAM
Features
■
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
28
1
PCDIP28 (PC)
battery/crystal
CAPHAT
VPFD = Power-fail deselect voltage):
– M48T08: VCC = 4.75 to 5.5V
4.5V ≤ VPFD ≤ 4.75V
– M48T18/T08Y: VCC = 4.5 to 5.5V
SNAPHAT (SH)
battery/crystal
4.2V ≤ VPFD ≤ 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
28
1
■
Pin and function compatible with DS1643 and
JEDEC standard 8K x8 SRAMs
■
RoHS compliant
– Lead-free second level interconnect
July 2007
SOH28 (MH)
Rev 8
1/30
www.st.com
1
Contents
M48T08, M48T08Y, M48T18
Contents
Summary description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Operation modes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Read mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Write mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Data retention mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Power-fail interrupt pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Clock operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Reading the clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Setting the clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Stopping and starting the oscillator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Calibrating the clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
VCC noise and negative going transients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Maximum rating. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
DC and AC parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Package mechanical data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Part numbering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2/30
M48T08, M48T08Y, M48T18
List of tables
List of tables
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
Table 6.
Table 7.
Table 8.
Table 9.
Table 10.
Table 11.
Table 12.
Table 13.
Table 14.
Table 15.
Table 16.
Table 17.
Table 18.
Signal names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Operating modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Read mode AC characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Write mode AC characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Operating and AC measurement conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Capacitance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
DC characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Power down/up AC characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Power down/up trip points DC characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
PCDIP28 – 28-pin plastic DIP, battery CAPHAT, package mechanical data . . . . . . . . . . . 23
SOH28 – 28-lead plastic SO, 4-socket battery SNAPHAT, package mech. data. . . . . . . . 24
SH – 4-pin SNAPHAT housing for 48mAh battery & crystal, package mech. data. . . . . . . 25
SH – 4-pin SNAPHAT housing for 120mAh battery & crystal, package mech data.. . . . . . 26
Ordering information scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
SNAPHAT battery table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3/30
List of figures
M48T08, M48T08Y, M48T18
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
Figure 15.
Figure 16.
4/30
Logic diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
DIP connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
SOIC connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Read mode AC waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Write enable controlled, write AC waveform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Chip enable controlled, write AC waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Crystal accuracy across temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Clock calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Supply voltage protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
AC testing load circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Power down/up mode AC waveforms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
PCDIP28 – 28-pin plastic DIP, battery CAPHAT, package outline . . . . . . . . . . . . . . . . . . . 23
SOH28 – 28-lead plastic small outline, 4-socket battery SNAPHAT, package outline . . . . 24
SH – 4-pin SNAPHAT housing for 48mAh battery & crystal, package outline . . . . . . . . . . 25
SH – 4-pin SNAPHAT housing for 120mAh battery & crystal, package outline . . . . . . . . . 26
M48T08, M48T08Y, M48T18
Summary description
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 solution.
The M48T08/18/08Y is a non-volatile pin and function 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
connection to a separate SNAPHAT® housing containing 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. Insertion of the SNAPHAT
housing after reflow prevents potential battery and crystal damage due to the high
temperatures required for device surface-mounting. The SNAPHAT housing is keyed to
prevent 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 battery/crystal package (e.g., SNAPHAT)
part number is “M4T28-BR12SH” or “M4T32-BR12SH” (see Table 17 on page 28).
Figure 1.
Logic diagram
VCC
13
8
A0-A12
W
E1
DQ0-DQ7
M48T08
M48T08Y
M48T18
INT
E2
G
VSS
AI01020
5/30
Summary description
Table 1.
M48T08, M48T08Y, M48T18
Signal names
A0-A12
Address inputs
DQ0-DQ7
Data inputs / outputs
INT
Power fail interrupt (open drain)
E1
Chip enable 1
E2
Chip enable 2
G
Output enable
W
WRITE enable
VCC
Supply voltage
VSS
Ground
Figure 2.
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
6/30
VCC
W
E2
A8
A9
A11
G
A10
E1
DQ7
DQ6
DQ5
DQ4
DQ3
M48T08, M48T08Y, M48T18
Figure 3.
Summary description
SOIC connections
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
VCC
W
E2
A8
A9
A11
G
A10
E1
DQ7
DQ6
DQ5
DQ4
DQ3
AI01021B
Figure 4.
Block diagram
OSCILLATOR AND
CLOCK CHAIN
8 x 8 BiPORT
SRAM ARRAY
32,768 Hz
CRYSTAL
A0-A12
POWER
8184 x 8
SRAM ARRAY
LITHIUM
CELL
DQ0-DQ7
E1
VOLTAGE SENSE
AND
SWITCHING
CIRCUITRY
VCC
INT
E2
VPFD
W
G
VSS
AI01333
7/30
Operation modes
M48T08, M48T08Y, M48T18
Operation modes
As Figure 4 on page 7 shows, the static memory array and the quartz-controlled clock
oscillator of the M48T08/18/08Y are integrated on one silicon chip. The two circuits are
interconnected at the upper eight memory locations to provide user accessible
BYTEWIDE™ clock information in the bytes with addresses 1FF8h-1FFFh.
The clock locations contain the year, month, date, day, hour, minute, and second in 24 hour
BCD format. Corrections for 28, 29 (leap year - valid until 2100), 30, and 31 day months are
made automatically. Byte 1FF8h is the clock control register. This byte controls user access
to the clock information and also stores the clock calibration setting.
The eight clock bytes are not the actual clock counters themselves; they are memory
locations consisting of BiPORT™ READ/WRITE memory cells. The M48T08/18/08Y
includes a clock control circuit which updates the clock bytes with current information once
per second. The information can be accessed by the user in the same manner as any other
location in the static memory array.
The M48T08/18/08Y also has its own Power-fail Detect circuit. The control circuitry
constantly monitors the single 5V supply for an out of tolerance condition. When VCC is out
of tolerance, the circuit write protects the SRAM, providing a high degree of data security in
the midst of unpredictable system operation brought on by low VCC. As VCC falls below the
Battery Back-up Switchover Voltage (VSO), the control circuitry connects the battery which
maintains data and clock operation until valid power returns.
Table 2.
Mode
Operating modes
VCC
Deselect
Deselect
WRITE
READ
4.75 to 5.5V
or
4.5 to 5.5V
READ
E1
E2
G
W
DQ0-DQ7
Power
VIH
X
X
X
High Z
Standby
X
VIL
X
X
High Z
Standby
VIL
VIH
X
VIL
DIN
Active
VIL
VIH
VIL
VIH
DOUT
Active
VIL
VIH
VIH
VIH
High Z
Active
Deselect
VSO to
VPFD(min)(1)
X
X
X
X
High Z
CMOS Standby
Deselect
≤ VSO(1)
X
X
X
X
High Z
Battery Back-up
Mode
1. See Table 11 on page 22 for details.
Note:
X = VIH or VIL ; VSO = battery back-up switchover voltage.
Read mode
The M48T08/18/08Y is in the READ Mode whenever W (WRITE Enable) is high, E1 (Chip
Enable 1) is low, and E2 (Chip Enable 2) is high. The device architecture allows ripplethrough access of data from eight of 65,536 locations in the static storage array. Thus, the
unique address specified by the 13 address inputs defines which one of the 8,192 bytes of
data is to be accessed. Valid data will be available at the Data I/O pins within address
access time (tAVQV) after the last address input signal is stable, providing that the E1, E2,
and G access times are also satisfied. If the E1, E2 and G access times are not met, valid
8/30
M48T08, M48T08Y, M48T18
Operation modes
data will be available after the latter of the Chip Enable Access times (tE1LQV or tE2HQV) or
Output Enable Access time (tGLQV).
The state of the eight three-state Data I/O signals is controlled by E1, E2 and G. If the
outputs are activated before tAVQV, the data lines will be driven to an indeterminate state
until tAVQV. If the address inputs are changed while E1, E2 and G remain active, output data
will remain valid for Output Data Hold time (tAXQX) but will go indeterminate until the next
address access.
Figure 5.
Read mode AC waveforms
tAVAV
A0-A12
VALID
tAVQV
tAXQX
tE1LQV
tE1HQZ
E1
tE1LQX
tE2HQV
tE2LQZ
E2
tE2HQX
tGLQV
tGHQZ
G
tGLQX
DQ0-DQ7
VALID
AI00962
Note:
WRITE Enable (W) = High.
9/30
Operation modes
Table 3.
M48T08, M48T08Y, M48T18
Read mode AC characteristics
M48T08/M48T18/T08Y
Parameter(1)
Symbol
–100/–10 (T08Y)
Min
Max
100
–150/–15 (T08Y)
Min
Unit
Max
tAVAV
READ Cycle Time
150
ns
tAVQV
Address Valid to Output Valid
100
150
ns
tE1LQV
Chip Enable 1 Low to Output Valid
100
150
ns
tE2HQV
Chip Enable 2 High to Output Valid
100
150
ns
tGLQV
Output Enable Low to Output Valid
50
75
ns
tE1LQX
Chip Enable 1 Low to Output Transition
10
10
ns
tE2HQX
Chip Enable 2 High to Output Transition
10
10
ns
tGLQX
Output Enable Low to Output Transition
5
5
ns
tE1HQZ
Chip Enable 1 High to Output Hi-Z
50
75
ns
tE2LQZ
Chip Enable 2 Low to Output Hi-Z
50
75
ns
tGHQZ
Output Enable High to Output Hi-Z
40
60
ns
tAXQX
Address Transition to Output Transition
Note:
5
5
ns
Valid for ambient operating temperature: TA = 0 to 70°C; VCC = 4.75 to 5.5V or 4.5 to 5.5V
(except where noted).
Write mode
The M48T08/18/08Y is in the WRITE Mode whenever W, E1, and E2 are active. The start of
a WRITE is referenced from the latter occurring falling edge of W or E1, or the rising edge of
E2. A WRITE is terminated by the earlier rising edge of W or E1, or the falling edge of E2.
The addresses must be held valid throughout the cycle. E1 or W must return high or E2 low
for a minimum of tE1HAX or tE2LAX from Chip Enable or tWHAX from WRITE Enable prior to
the initiation of another READ or WRITE Cycle. Data-in must be valid tDVWH prior to the end
of WRITE and remain valid for tWHDX afterward. G should be kept high during WRITE
Cycles to avoid bus contention; however, if the output bus has been activated by a low on
E1 and G and a high on E2, a low on W will disable the outputs tWLQZ after W falls.
10/30
M48T08, M48T08Y, M48T18
Figure 6.
Operation modes
Write enable controlled, write AC waveform
tAVAV
VALID
A0-A12
tAVWH
tWHAX
tAVE1L
E1
tAVE2H
E2
tWLWH
tAVWL
W
tWHQX
tWLQZ
tWHDX
DQ0-DQ7
DATA INPUT
tDVWH
AI00963
Figure 7.
Chip enable controlled, write AC waveforms
tAVAV
A0-A12
VALID
tAVE1H
tAVE1L
tE1LE1H
tE1HAX
E1
tAVE2L
tAVE2H
tE2HE2L
tE2LAX
E2
tAVWL
W
tE1HDX
tE2LDX
DQ0-DQ7
DATA INPUT
tDVE1H
tDVE2L
AI00964B
11/30
Operation modes
Table 4.
M48T08, M48T08Y, M48T18
Write mode AC characteristics
M48T08/M48T18/T08Y
Symbol
Parameter(1)
–100/–10 (T08Y)
Min
tAVAV
WRITE Cycle Time
tAVWL
Max
–150/–15 (T08Y)
Min
Unit
Max
100
150
ns
Address Valid to WRITE Enable Low
0
0
ns
tAVE1L
Address Valid to Chip Enable 1 Low
0
0
ns
tAVE2H
Address Valid to Chip Enable 2 High
0
0
ns
tWLWH
WRITE Enable Pulse Width
80
100
ns
tE1LE1H
Chip Enable 1 Low to Chip Enable 1 High
80
130
ns
tE2HE2L
Chip Enable 2 High to Chip Enable 2 Low
80
130
ns
tWHAX
WRITE Enable High to Address Transition
10
10
ns
tE1HAX
Chip Enable 1 High to Address Transition
10
10
ns
tE2LAX
Chip Enable 2 Low to Address Transition
10
10
ns
tDVWH
Input Valid to WRITE Enable High
50
70
ns
tDVE1H
Input Valid to Chip Enable 1 High
50
70
ns
tDVE2L
Input Valid to Chip Enable 2 Low
50
70
ns
tWHDX
WRITE Enable High to Input Transition
5
5
ns
tE1HDX
Chip Enable 1 High to Input Transition
5
5
ns
tE2LDX
Chip Enable 2 Low to Input Transition
5
5
ns
tWLQZ
WRITE Enable Low to Output Hi-Z
tAVWH
Address Valid to WRITE Enable High
80
130
ns
tAVE1H
Address Valid to Chip Enable 1 High
80
130
ns
tAVE2L
Address Valid to Chip Enable 2 Low
80
130
ns
tWHQX
WRITE Enable High to Output Transition
10
10
ns
50
70
ns
1. Valid for ambient operating temperature: TA = 0 to 70°C; VCC = 4.75 to 5.5V or 4.5 to 5.5V (except where noted).
Data retention mode
With valid VCC applied, the M48T08/18/08Y operates as a conventional BYTEWIDE™ static
RAM. Should the supply voltage decay, the RAM will automatically power-fail deselect, write
protecting itself when VCC falls within the VPFD (max), VPFD (min) window. All outputs
become high impedance, and all inputs are treated as “Don't care.”
Note:
12/30
A power failure during a WRITE cycle may corrupt data at the currently addressed location,
but does not jeopardize the rest of the RAM's content. At voltages below VPFD (min), the
user can be assured the memory will be in a write protected state, provided the VCC fall time
is not less than tF. The M48T08/18/08Y may respond to transient noise spikes on VCC that
reach into the deselect window during the time the device is sampling VCC. Therefore,
decoupling of the power supply lines is recommended.
M48T08, M48T08Y, M48T18
Operation modes
When VCC drops below VSO, the control circuit switches power to the internal battery which
preserves data and powers the clock. The internal button cell will maintain data in the
M48T08/18/08Y for an accumulated period of at least 10 years when VCC is less than VSO.
Note:
Requires use of M4T32-BR12SH SNAPHAT® top when using the SOH28 package.
As system power returns and VCC rises above VSO, the battery is disconnected and the
power supply is switched to external VCC.
Write protection continues until VCC reaches VPFD (min) plus trec (min). E1 should be kept
high or E2 low as VCC rises past VPFD (min) to prevent inadvertent WRITE cycles prior to
system stabilization. Normal RAM operation can resume trec after VCC exceeds VPFD (max).
For more information on Battery Storage Life refer to the Application Note AN1012.
Power-fail interrupt pin
The M48T08/18/08Y continuously monitors VCC. When VCC falls to the power-fail detect trip
point, an interrupt is immediately generated. An internal clock provides a delay of between
10µs and 40µs before automatically deselecting the M48T08/18/08Y. The INT pin is an
open drain output and requires an external pull up resistor, even if the interrupt output
function is not being used.
13/30
Clock operations
M48T08, M48T08Y, M48T18
Clock operations
Reading the clock
Updates to the TIMEKEEPER® registers should be halted before clock data is read to
prevent reading data in transition. The BiPORT™ TIMEKEEPER cells in the RAM array are
only data registers and not the actual clock counters, so updating the registers can be
halted without disturbing the clock itself.
Updating is halted when a '1' is written to the READ Bit, the seventh bit in the control
register. As long as a '1' remains in that position, updating is halted. After a halt is issued,
the registers reflect the count; that is, the day, date, and the time that were current at the
moment the halt command was issued.
All of the TIMEKEEPER registers are updated simultaneously. A halt will not interrupt an
update in progress. Updating is within a second after the bit is reset to a '0.'
Setting the clock
The eighth bit of the control register is the WRITE Bit. Setting the WRITE Bit to a '1,' like the
READ Bit, halts updates to the TIMEKEEPER registers. The user can then load them with
the correct day, date, and time data in 24 hour BCD format (on Table 5). Resetting the
WRITE Bit to a '0' then transfers the values of all time registers (1FF9h-1FFFh) to the actual
TIMEKEEPER counters and allows normal operation to resume. The FT Bit and the bits
marked as '0' in Table 5 must be written to '0' to allow for normal TIMEKEEPER and RAM
operation.
See the Application Note AN923, “TIMEKEEPER® Rolling Into the 21st Century” for
information on Century Rollover.
14/30
M48T08, M48T08Y, M48T18
Table 5.
Clock operations
Register map
Data
Function/range
Address
D7
1FFFh
Note:
D6
D5
D4
D3
10 Years
1FFEh
0
0
0
10 M
1FFDh
0
0
10 Date
1FFCh
0
FT
1FFBh
0
0
1FFAh
0
1FF9h
ST
1FF8h
W
0
0
10 Hours
10 Minutes
10 Seconds
R
S
D2
D1
D0
BCD format
Year
Year
00-99
Month
Month
01-12
Date
Date
01-31
Day
01-07
Hours
Hours
00-23
Minutes
Minutes
00-59
Seconds
Seconds
00-59
0
Day
Calibration
Control
S = SIGN Bit
FT = FREQUENCY TEST Bit (Set to '0' for normal clock operation)
R = READ Bit
W = WRITE Bit
ST = STOP Bit
0 = Must be set to '0'
Stopping and starting the oscillator
The oscillator may be stopped at any time. If the device is going to spend a significant
amount of time on the shelf, the oscillator can be turned off to minimize current drain on the
battery. The STOP Bit (ST) is the MSB of the seconds register. Setting it to a '1' stops the
oscillator. The M48T08/18/08Y (in the PCDIP28 package) is shipped from
STMicroelectronics with the STOP Bit set to a '1.' When reset to a '0,' the M48T08/18/08Y
oscillator starts within one second.
Note:
To guarantee oscillator start-up after initial power-up, first write the STOP Bit (ST) to '1,'
then reset to '0.'
Calibrating the clock
The M48T08/18/08Y is driven by a quartz-controlled oscillator with a nominal frequency of
32,768 Hz. A typical M48T08/18/08Y is accurate within 1 minute per month at 25°C without
calibration. The devices are tested not to exceed ± 35 ppm (parts per million) oscillator
frequency error at 25°C, which equates to about ±1.53 minutes per month. With the
calibration bits properly set, the accuracy of each M48T08/18/08Y improves to better than
+1/–2 ppm at 25°C.
The oscillation rate of any crystal changes with temperature. Figure 8 on page 17 shows the
frequency error that can be expected at various temperatures. Most clock chips compensate
for crystal frequency and temperature shift error with cumbersome “trim” capacitors. The
M48T08/18/08Y design, however, employs periodic counter correction. The calibration
circuit adds or subtracts counts from the oscillator divider circuit at the divide by 256 stage,
as shown in Figure 9 on page 17. The number of times pulses are blanked (subtracted,
negative calibration) or split (added, positive calibration) depends upon the value loaded
15/30
Clock operations
M48T08, M48T08Y, M48T18
into the five-bit Calibration Byte found in the Control Register. Adding counts speeds the
clock up, subtracting counts slows the clock down.
The Calibration Byte occupies the five lower order bits in the Control register. This byte can
be set to represent any value between 0 and 31 in binary form. The sixth bit is the Sign Bit;
'1' indicates positive calibration, '0' indicates negative calibration. Calibration occurs within a
64 minute cycle. The first 62 minutes in the cycle may, once per minute, have one second
either shortened by 128 or lengthened by 256 oscillator cycles. If a binary '1' is loaded into
the register, only the first 2 minutes in the 64 minute cycle will be modified; if a binary 6 is
loaded, the first 12 will be affected, and so on.
Therefore, each calibration step has the effect of adding 512 or subtracting 256 oscillator
cycles for every 125,829,120 actual oscillator cycles; that is +4.068 or –2.034 ppm of
adjustment per calibration step in the calibration register. Assuming that the oscillator is in
fact running at exactly 32,768Hz, each of the 31 increments in the Calibration Byte would
represent +10.7 or –5.35 seconds per month which corresponds to a total range of +5.5 or –
2.75 minutes per month.
Two methods are available for ascertaining how much calibration a given M48T08/18/08Y
may require. The first involves simply setting the clock, letting it run for a month and
comparing it to a known accurate reference (like WWV broadcasts). While that may seem
crude, it allows the designer to give the end user the ability to calibrate his clock as his
environment may require, even after the final product is packaged in a non-user serviceable
enclosure. All the designer has to do is provide a simple utility that accesses the Calibration
Byte.
The second approach is better suited to a manufacturing environment, and involves the use
of standard test equipment. When the Frequency Test (FT) Bit, the seventh-most significant
bit in the Day Register, is set to a '1,' and the oscillator is running at 32,768 Hz, the LSB
(DQ0) of the Seconds Register will toggle at 512 Hz. Any deviation from 512 Hz indicates
the degree and direction of oscillator frequency shift at the test temperature. For example, a
reading of 512.01024 Hz would indicate a +20 ppm oscillator frequency error, requiring a –
10 (WR001010) to be loaded into the Calibration Byte for correction.
Note:
Setting or changing the Calibration Byte does not affect the Frequency Test output
frequency. The device must be selected and addresses must be stable at Address 1FF9h
when reading the 512 Hz on DQ0.
The LSB of the Seconds Register is monitored by holding the M48T08/18/08Y in an
extended READ of the Seconds Register, but without having the READ Bit set. The FT Bit
MUST be reset to '0' for normal clock operations to resume.
For more information on calibration, see the Application Note AN934, “TIMEKEEPER®
Calibration.”
16/30
M48T08, M48T08Y, M48T18
Figure 8.
Clock operations
Crystal accuracy across temperature
ppm
20
0
-20
-40
ΔF = -0.038 ppm (T - T )2 ± 10%
0
F
C2
-60
T0 = 25 °C
-80
-100
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
°C
AI02124
Figure 9.
Clock calibration
NORMAL
POSITIVE
CALIBRATION
NEGATIVE
CALIBRATION
AI00594B
VCC noise and negative going transients
ICC transients, including those produced by output switching, can produce voltage
fluctuations, resulting in spikes on the VCC bus. These transients can be reduced if
capacitors are used to store energy which stabilizes the VCC bus. The energy stored in the
bypass capacitors will be released as low going spikes are generated or energy will be
absorbed when overshoots occur. A ceramic bypass capacitor value of 0.1µF (as shown in
Figure 10) is recommended in order to provide the needed filtering.
In addition to transients that are caused by normal SRAM operation, power cycling can
generate negative voltage spikes on VCC that drive it to values below VSS by as much as
one volt. These negative spikes can cause data corruption in the SRAM while in battery
backup mode. To protect from these voltage spikes, it is recommended to connect a
schottky diode from VCC to VSS (cathode connected to VCC, anode to VSS). Schottky diode
17/30
Clock operations
M48T08, M48T08Y, M48T18
1N5817 is recommended for through hole and MBRS120T3 is recommended for surface
mount.
Figure 10. Supply voltage protection
VCC
VCC
0.1μF
DEVICE
VSS
AI02169
18/30
M48T08, M48T08Y, M48T18
Maximum rating
Maximum rating
Stressing the device above the rating listed in the “Absolute Maximum Ratings” table may
cause permanent damage to the device. These are stress ratings only and operation of the
device at these or any other conditions above those indicated in the Operating sections of
this specification is not implied. Exposure to Absolute Maximum Rating conditions for
extended periods may affect device reliability. Refer also to the STMicroelectronics SURE
Program and other relevant quality documents.
Table 6.
Absolute maximum ratings
Symbol
TA
TSTG
TSLD(1) (2) (3)
Parameter
Value
Unit
0 to 70
°C
–40 to 85
°C
260
°C
Ambient Operating Temperature
Storage Temperature (VCC Off, Oscillator Off)
Lead Solder Temperature for 10 seconds
VIO
Input or Output Voltages
–0.3 to 7
V
VCC
Supply Voltage
–0.3 to 7
V
IO
Output Current
20
mA
PD
Power Dissipation
1
W
1. For DIP package: Soldering temperature not to exceed 260°C for 10 seconds (total thermal budget not to
exceed 150°C for longer than 30 seconds).
2. For SO package, standard (SnPb) lead finish: Reflow at peak temperature of 225°C (total thermal budget
not to exceed 180°C for between 90 to 150 seconds).
3. For SO package, Lead-free (Pb-free) lead finish: Reflow at peak temperature of 260°C (total thermal
budget not to exceed 245°C for greater than 30 seconds).
Caution:
Negative undershoots below –0.3V are not allowed on any pin while in the Battery Back-up
mode.
Caution:
Do NOT wave solder SOIC to avoid damaging SNAPHAT sockets.
19/30
DC and AC parameters
M48T08, M48T08Y, M48T18
DC and AC parameters
This section summarizes the operating and measurement conditions, as well as the DC and
AC characteristics of the device. The parameters in the following DC and AC Characteristic
tables are derived from tests performed under the Measurement Conditions listed in the
relevant tables. Designers should check that the operating conditions in their projects match
the measurement conditions when using the quoted parameters.
Table 7.
Operating and AC measurement conditions
Parameter
M48T08
M48T18/T08Y
Unit
4.75 to 5.5
4.5 to 5.5
V
0 to 70
0 to 70
°C
Load Capacitance (CL)
100
100
pF
Input Rise and Fall Times
≤5
≤5
ns
0 to 3
0 to 3
V
1.5
1.5
V
Supply Voltage (VCC)
Ambient Operating Temperature (TA)
Input Pulse Voltages
Input and Output Timing Ref. Voltages
Note:
Output Hi-Z is defined as the point where data is no longer driven.
Figure 11. AC testing load circuit
5V
1.8kΩ
DEVICE
UNDER
TEST
OUT
1kΩ
CL includes JIG capacitance
Table 8.
CIO(3)
AI01019
Capacitance
Parameter(1)(2)
Symbol
CIN
CL = 100pF
Min
Max
Unit
Input Capacitance
10
pF
Input / Output Capacitance
10
pF
1. Effective capacitance measured with power supply at 5V; sampled only, not 100% tested.
2. At 25°C, f = 1MHz.
3. Outputs deselected.
20/30
M48T08, M48T08Y, M48T18
Table 9.
DC and AC parameters
DC characteristics
Symbol
M48T08/M48T18/T08Y
Test condition(1)
Parameter
Unit
Min
ILI
ILO(2)
ICC
ICC1
(3)
ICC2(3)
Max
0V ≤ VIN ≤ VCC
±1
µA
0V ≤ VOUT ≤ VCC
±1
µA
Outputs open
80
mA
Supply Current (Standby) TTL
E1 = VIH, E2 = VIL
3
mA
Supply Current (Standby) CMOS
E1 = VCC – 0.2V,
E2 = VSS + 0.2V
3
mA
Input Leakage Current
Output Leakage Current
Supply Current
VIL
Input Low Voltage
–0.3
0.8
V
VIH
Input High Voltage
2.2
VCC + 0.3
V
0.4
V
0.4
V
VOL
VOH
Output Low Voltage
Output Low Voltage (INT)
IOL = 2.1mA
(4)(4)
IOL = 0.5mA
Output High Voltage
IOH = –1mA
2.4
V
1. Valid for Ambient Operating Temperature: TA = 0 to 70°C; VCC = 4.75 to 5.5V or 4.5 to 5.5V (except where noted).
2. Outputs deselected.
3. Measured with Control Bits set as follows: R = '1'; W, ST, FT = '0.'
4. The INT pin is open drain.
Figure 12. Power down/up mode AC waveforms
VCC
VPFD (max)
VPFD (min)
VSO
tF
tDR
tR
tFB
tPD
tRB
tPFX
tPFH
INT
trec
INPUTS
RECOGNIZED
DON'T CARE
NOTE
RECOGNIZED
HIGH-Z
OUTPUTS
VALID
(PER CONTROL INPUT)
VALID
(PER CONTROL INPUT)
AI00566
Note:
Inputs may or may not be recognized at this time. Caution should be taken to keep E1 high
or E2 low as VCC rises past VPFD (min). Some systems may perform inadvertent WRITE
cycles after VCC rises above VPFD (min) but before normal system operations begin. Even
though a power on reset is being applied to the processor, a reset condition may not occur
until after the system clock is running.
21/30
DC and AC parameters
Table 10.
Symbol
M48T08, M48T08Y, M48T18
Power down/up AC characteristics
Parameter(1)
Min
Max
Unit
tPD
E1 or W at VIH or E2 at VIL before Power
Down
0
µs
tF(2)
VPFD (max) to VPFD (min) VCC Fall Time
300
µs
tFB(3)
VPFD (min) to VSS VCC Fall Time
10
µs
tR
VPFD (min) to VPFD (max) VCC Rise Time
0
µs
tRB
VSS to VPFD (min) VCC Rise Time
1
µs
trec
E1 or W at VIH or E2 at VIL before Power Up
1
ms
tPFX
INT Low to Auto Deselect
10
tPFH
VPFD (max) to INT High
40
µs
120
µs
1. Valid for Ambient Operating Temperature: TA = 0 to 70°C; VCC = 4.75 to 5.5V or 4.5 to 5.5V (except where
noted).
2. VPFD (max) to VPFD (min) fall time of less than tF may result in deselection/write protection not occurring
until 200µs after VCC passes VPFD (min).
3. VPFD (min) to VSS fall time of less than tFB may cause corruption of RAM data.
Table 11.
Symbol
Power down/up trip points DC characteristics
Parameter(1)(2)
Min
Typ
Max
Unit
M48T08
4.5
4.6
4.75
V
M48T18/T08Y
4.2
4.3
4.5
V
VPFD
Power-fail Deselect Voltage
VSO
Battery Back-up Switchover Voltage
tDR
Expected Data Retention Time
3.0
10(3)
V
YEARS
1. All voltages referenced to VSS.
2. Valid for Ambient Operating Temperature: TA = 0 to 70°C; VCC = 4.75 to 5.5V or 4.5 to 5.5V (except
where noted).
3. At 55°C, VCC = 0V; tDR = 8.5 years (typ) at 70°C. Requires use of M4T32-BR12SH SNAPHAT® top when
using the SOH28 package.
22/30
M48T08, M48T08Y, M48T18
Package mechanical data
Package mechanical data
In order to meet environmental requirements, ST offers these devices in ECOPACK®
packages. These packages have a Lead-free second level interconnect. The category of
second Level Interconnect is marked on the package and on the inner box label, in
compliance with JEDEC Standard JESD97. The maximum ratings related to soldering
conditions are also marked on the inner box label. ECOPACK is an ST trademark.
ECOPACK specifications are available at: www.st.com.
Figure 13. PCDIP28 – 28-pin plastic DIP, battery CAPHAT, package outline
A2
A
A1
B1
B
L
C
e1
eA
e3
D
N
E
1
Note:
PCDIP
Drawing is not to scale.
Table 12.
PCDIP28 – 28-pin plastic DIP, battery CAPHAT, package mechanical data
mm
inches
Symb
Typ
Min
Max
A
8.89
A1
Typ
Min
Max
9.65
0.350
0.380
0.38
0.76
0.015
0.030
A2
8.38
8.89
0.330
0.350
B
0.38
0.53
0.015
0.021
B1
1.14
1.78
0.045
0.070
C
0.20
0.31
0.008
0.012
D
39.37
39.88
1.550
1.570
E
17.83
18.34
0.702
0.722
e1
2.29
2.79
0.090
0.110
e3
29.72
36.32
1.170
1.430
eA
15.24
16.00
0.600
0.630
L
3.05
3.81
0.120
0.150
N
28
28
23/30
Package mechanical data
M48T08, M48T08Y, M48T18
Figure 14. SOH28 – 28-lead plastic small outline, 4-socket battery SNAPHAT, package
outline
A2
A
C
B
eB
e
CP
D
N
E
H
A1
α
L
1
SOH-A
Note:
Drawing is not to scale.
Table 13.
SOH28 – 28-lead plastic SO, 4-socket battery SNAPHAT, package mech. data
mm
inches
Symb
Typ
Min
A
Typ
Min
3.05
Max
0.120
A1
0.05
0.36
0.002
0.014
A2
2.34
2.69
0.092
0.106
B
0.36
0.51
0.014
0.020
C
0.15
0.32
0.006
0.012
D
17.71
18.49
0.697
0.728
E
8.23
8.89
0.324
0.350
–
–
–
–
eB
3.20
3.61
0.126
0.142
H
11.51
12.70
0.453
0.500
L
0.41
1.27
0.016
0.050
a
0°
8°
0°
8°
N
28
e
CP
24/30
Max
1.27
0.050
28
0.10
0.004
M48T08, M48T08Y, M48T18
Package mechanical data
Figure 15. SH – 4-pin SNAPHAT housing for 48mAh battery & crystal, package outline
A1
A2
A3
A
eA
B
L
eB
D
E
SHTK-A
Note:
Drawing is not to scale.
Table 14.
SH – 4-pin SNAPHAT housing for 48mAh battery & crystal, package mech.
data
mm
inches
Symb
Typ
Min
A
Max
Typ
Min
9.78
Max
0.385
A1
6.73
7.24
0.265
0.285
A2
6.48
6.99
0.255
0.275
A3
0.38
0.015
B
0.46
0.56
0.018
0.022
D
21.21
21.84
0.835
0.860
E
14.22
14.99
0.560
0.590
eA
15.55
15.95
0.612
0.628
eB
3.20
3.61
0.126
0.142
L
2.03
2.29
0.080
0.090
25/30
Package mechanical data
M48T08, M48T08Y, M48T18
Figure 16. SH – 4-pin SNAPHAT housing for 120mAh battery & crystal, package
outline
A1
A2
A3
A
eA
B
L
eB
D
E
SHTK-A
Note:
Drawing is not to scale.
Table 15.
SH – 4-pin SNAPHAT housing for 120mAh battery & crystal, package mech
data.
mm
inches
Symb
Typ
Min
A
Typ
Min
10.54
Max
0.415
A1
8.00
8.51
0.315
.0335
A2
7.24
8.00
0.285
0.315
A3
26/30
Max
0.38
0.015
B
0.46
0.56
0.018
0.022
D
21.21
21.84
0.835
0.860
E
17.27
18.03
0.680
.0710
eA
15.55
15.95
0.612
0.628
eB
3.20
3.61
0.126
0.142
L
2.03
2.29
0.080
0.090
M48T08, M48T08Y, M48T18
Part numbering
Part numbering
Table 16.
Ordering information scheme
Example:
M48T
18
–100
PC
1
E
Device type
M48T
Supply Voltage and Write Protect Voltage
08(1) = VCC = 4.75 to 5.5V; VPFD = 4.5 to 4.75V
18/08Y = VCC = 4.5 to 5.5V; VPFD = 4.2 to 4.5V
Speed
–100 = 100ns
–150 = 150ns
–10 = 100ns (M48T08Y)
Package
PC(1) = PCDIP28
MH(2) = SOH28
Temperature Range
1 = 0 to 70°C
Shipping Method
For SOH28:
blank = Tubes (Not for New Design - Use E)
E = ECOPACK Package, Tubes
F = ECOPACK Package, Tape & Reel
TR = Tape & Reel (Not for New Design - Use F)
For PCDIP28:
blank = ECOPACK Package, Tubes
1. The M48T08/18 part is offered with the PCDIP28 (e.g., CAPHAT™) package only.
2. The SOIC package (SOH28) requires the SNAPHAT® battery/crystal package which is ordered separately
under the part number“M4TXX-BR12SH” in plastic tube or “M4TXX-BR12SHTR” in Tape & Reel form (see
Table 17). The M48T08Y part is offered in the SOH28 (SNAPHAT) package only.
Caution:
Do not place the SNAPHAT battery package “M4TXX-BR12SH” in conductive foam as it will
drain the lithium button-cell battery.
For other options, or for more information on any aspect of this device, please contact the
ST sales office nearest you.
27/30
Part numbering
M48T08, M48T08Y, M48T18
Table 17.
SNAPHAT battery table
Part Number
M4T28-BR12SH
M4T32-BR12SH
28/30
Description
Lithium Battery (48mAh) SNAPHAT
Lithium Battery (120mAh) SNAPHAT
Package
SH
SH
M48T08, M48T08Y, M48T18
Revision history
Revision history
Table 18.
Document revision history
Date
Revision
Changes
Dec-1999
1.0
First Issue
07-Feb-2000
2.0
From Preliminary Data to Data Sheet; Battery Low Flag paragraph
changed; 100ns speed class identifier changed (Table 3, 4)
11-Jul-2000
2.1
tFB changed (Table 10); Watchdog Timer paragraph changed
16-Jul-2001
3.0
Reformatted; SNAPHAT battery table added (Table 17); added
temp./voltage info. to tables (Table 8, 9, 3, 4, 10, 11).
01-Aug-2001
3.1
Reference to App. Note corrected in “Calibrating the Clock” section
21-Dec-2001
3.2
Changes to text in document to reflect addition of M48T08Y option
06-Mar-2002
3.3
Fix Ordering Information table and add to footnote (Table 16)
20-May-2002
3.4
Modify reflow time and temperature footnotes (Table 6)
29-Aug-2002
3.5
tDR specification temperature updated (Table 11)
28-Mar-2003
4.0
v2.2 template applied; updated test conditions (Table 10)
10-Dec-2003
5.0
Reformatted
30-Mar-2004
6.0
Reformatted; Lead-free (Pb-free) information package update (Table 6,
16)
13-Dec-2005
7.0
Updated template, Lead-free information, removed footnote (Table 9, 16)
04-Jul-2007
8.0
Reformatted; added lead-free second level interconnect information to
cover page and Section : Package mechanical data.
29/30
M48T08, M48T08Y, M48T18
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