STMicroelectronics M48T58-70MH1E 5.0v, 64 kbit (8 kb x 8) timekeeper sram Datasheet

M48T58
M48T58Y
5.0V, 64 Kbit (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
■
Frequency test output for real time clock
■
Automatic power-fail chip deselect and write
protection
■
Write protect voltages
28
1
PCDIP28 (PC)
Battery/Crystal
CAPHAT
(VPFD = power-fail deselect voltage):
– M48T58: VCC = 4.75 to 5.5V
4.5V ≤ VPFD ≤ 4.75V
– M48T58Y: VCC = 4.5 to 5.5V
SNAPHAT (SH)
Battery/Crystal
4.2V ≤ VPFD ≤ 4.5V
■
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 housing containing the battery and
crystal
■
Pin and function compatible with JEDEC
standard 8 Kb x8 SRAMs
■
RoHS compliant
– Lead-free second level interconnect
August 2007
28
1
SOH28 (MH)
Rev 5
1/31
www.st.com
1
Contents
M48T58, M48T58Y
Contents
1
Summary description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2
Operation modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3
Read mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4
Write mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5
Data retention mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6
Clock operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6.1
Reading the clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6.2
Setting the clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6.3
Stopping and starting the oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6.4
Calibrating the Clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.5
Battery low flag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
6.6
Century bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
6.7
VCC noise and negative going transients . . . . . . . . . . . . . . . . . . . . . . . . . 19
7
Maximum rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
8
DC and AC parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
9
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
10
Part numbering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
11
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
2/31
M48T58, M48T58Y
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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Operating and AC measurement conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Capacitance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
DC characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Power down/up AC characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Power down/up trip points DC characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
PCDIP28 – 28-pin plastic DIP, battery CAPHAT, package mechanical data . . . . . . . . . . . 24
SOH28 – 28-lead plastic small outline, 4-socket battery SNAPHAT, package mech. data 25
SH – 4-pin SNAPHAT housing for 48mAh battery & crystal, package mech. data. . . . . . . 26
SH – 4-pin SNAPHAT housing for 120mAh battery & crystal, package mech. data. . . . . . 27
Ordering information scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
SNAPHAT battery table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
3/31
List of figures
M48T58, M48T58Y
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.
4/31
Logic diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
DIP connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
SOIC connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Read mode AC waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Write enable controlled, write AC waveform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Chip enable controlled, write AC waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Crystal accuracy across temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Clock calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Supply voltage protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
AC measurement load circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Power down/up mode AC waveforms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
PCDIP28 – 28-pin plastic DIP, battery CAPHAT, package outline . . . . . . . . . . . . . . . . . . . 24
SOH28 – 28-lead plastic small outline, 4-socket battery SNAPHAT, package outline . . . . 25
SH – 4-pin SNAPHAT housing for 48mAh battery & crystal, package outline . . . . . . . . . . 26
SH – 4-pin SNAPHAT housing for 120mAh battery & crystal, package outline . . . . . . . . . 27
M48T58, M48T58Y
1
Summary description
Summary description
The M48T58/Y TIMEKEEPER® RAM is a 8Kb x 8 non-volatile static RAM and real time
clock. The monolithic chip is available in two special packages to provide a highly integrated
battery backed-up memory and real time clock solution.
The M48T58/Y is a non-volatile pin and function equivalent to any JEDEC standard 8Kb 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 M48T58/Y 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 “M4T28BR12SH” (see Table 17 on page 29).
Figure 1.
Logic diagram
VCC
13
8
A0-A12
DQ0-DQ7
W
E1
M48T58
M48T58Y
FT
E2
G
VSS
AI01374B
5/31
Summary description
Table 1.
M48T58, M48T58Y
Signal names
A0-A12
DQ0-DQ7
Figure 2.
Address Inputs
Data Inputs / Outputs
FT
Frequency Test Output (Open Drain)
E1
Chip Enable 1
E2
Chip Enable 2
G
Output Enable
W
WRITE Enable
VCC
Supply Voltage
VSS
Ground
DIP connections
FT
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
M48T58 22
8 M48T58Y 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
AI01375B
Figure 3.
SOIC connections
FT
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
M48T58Y
8
21
9
20
10
19
11
18
12
17
13
16
14
15
AI01376B
6/31
VCC
W
E2
A8
A9
A11
G
A10
E1
DQ7
DQ6
DQ5
DQ4
DQ3
M48T58, M48T58Y
Figure 4.
Summary description
Block diagram
FT
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
E2
VPFD
W
G
VSS
AI01377C
7/31
Operation modes
2
M48T58, M48T58Y
Operation modes
As Figure 4 on page 7 shows, the static memory array and the quartz controlled clock
oscillator of the M48T58/Y 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 century, year, month, date, day, hour, minute, and second in 24 hour
BCD format (except for the century). 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 M48T58/Y 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 M48T58/Y 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 23 for details.
Note:
8/31
X = VIH or VIL; VSO = Battery Back-up Switchover Voltage.
M48T58, M48T58Y
3
Read mode
Read mode
The M48T58/Y 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 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 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.
9/31
Read mode
M48T58, M48T58Y
Table 3.
Read mode AC characteristics
M48T58/Y
Parameter(1)
Symbol
Unit
Min
Max
tAVAV
READ Cycle Time
tAVQV
Address Valid to Output Valid
70
ns
tE1LQV
Chip Enable 1 Low to Output Valid
70
ns
tE2HQV
Chip Enable 2 High to Output Valid
70
ns
tGLQV
Output Enable Low to Output Valid
35
ns
tE1LQX(2)
tE2HQX(2)
tGLQX(2)
tE1HQZ(2)
tE2LQZ(2)
tGHQZ(2)
Chip Enable 1 Low to Output Transition
tAXQX
Address Transition to Output Transition
70
ns
5
ns
Chip Enable 2 High to Output Transition
5
ns
Output Enable Low to Output Transition
5
ns
Chip Enable 1 High to Output Hi-Z
25
ns
Chip Enable 2 Low to Output Hi-Z
25
ns
Output Enable High to Output Hi-Z
25
ns
10
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).
2. CL = 5pF.
10/31
M48T58, M48T58Y
4
Write mode
Write mode
The M48T58/Y is in the WRITE Mode whenever W and E1 are low and E2 is high. 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; although, 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.
Figure 6.
Write enable controlled, write AC waveform
tAVAV
A0-A12
VALID
tAVWH
tWHAX
tAVE1L
E1
tAVE2H
E2
tWLWH
tAVWL
W
tWHQX
tWLQZ
tWHDX
DQ0-DQ7
DATA INPUT
tDVWH
AI00963
11/31
Write mode
Figure 7.
M48T58, M48T58Y
Chip enable controlled, write AC waveforms
tAVAV
VALID
A0-A12
tAVE1H
tAVE1L
tE1LE1H
tE1HAX
E1
tAVE2L
tAVE2H
tE2HE2L
tE2LAX
E2
tAVWL
W
tE1HDX
tE2LDX
DQ0-DQ7
DATA INPUT
tDVE1H
tDVE2L
12/31
AI00964B
M48T58, M48T58Y
Table 4.
Symbol
Write mode
Write mode AC characteristics
M48T58/Y
Parameter(1)
Unit
Min
Max
tAVAV
WRITE Cycle Time
70
ns
tAVWL
Address Valid to WRITE Enable Low
0
ns
tAVE1L
Address Valid to Chip Enable 1 Low
0
ns
tAVE2H
Address Valid to Chip Enable 2 High
0
ns
tWLWH
WRITE Enable Pulse Width
50
ns
tE1LE1H
Chip Enable 1 Low to Chip Enable 1 High
55
ns
tE2HE2L
Chip Enable 2 High to Chip Enable 2 Low
55
ns
tWHAX
WRITE Enable High to Address Transition
0
ns
tE1HAX
Chip Enable 1 High to Address Transition
0
ns
tE2LAX
Chip Enable 2 Low to Address Transition
0
ns
tDVWH
Input Valid to WRITE Enable High
30
ns
tDVE1H
Input Valid to Chip Enable 1 High
30
ns
tDVE2L
Input Valid to Chip Enable 2 Low
30
ns
tWHDX
WRITE Enable High to Input Transition
5
ns
tE1HDX
Chip Enable 1 High to Input Transition
5
ns
tE2LDX
Chip Enable 2 Low to Input Transition
5
ns
tWLQZ(2)(3)
Write Enable Low to Output Hi-Z
25
ns
tAVWH
Address Valid to WRITE Enable High
60
ns
tAVE1H
Address Valid to Chip Enable 1 High
60
ns
tAVE2L
Address Valid to Chip Enable 2 Low
60
ns
WRITE Enable High to Output Transition
5
ns
tWHQX(2)(3)
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. CL = 5pF.
3. If E1 goes low or E2 high simultaneously with W going low, the outputs remain in the high impedance
state.
13/31
Data retention mode
5
M48T58, M48T58Y
Data retention mode
With valid VCC applied, the M48T58/Y 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:
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 M48T58/Y 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.
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
M48T58/Y for an accumulated period of at least 7 years when VCC is less than VSO. 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.
14/31
M48T58, M48T58Y
6
Clock operations
6.1
Reading the clock
Clock operations
Updates to the TIMEKEEPER® registers (see Table 5) 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, D6 in the Control Register 1FF8h.
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.'
6.2
Setting the clock
Bit D7 of the Control register (1FF8h) 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 (see 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 bits marked as '0' in
Table 5 on page 16 must be written to '0' to allow for normal TIMEKEEPER and RAM
operation. After the WRITE Bit is reset, the next clock update will occur within one second.
See the Application Note AN923 “TIMEKEEPER Rolling Into the 21st Century” for
information on Century Rollover.
6.3
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 is the MSB of the seconds register. Setting it to a '1' stops the
oscillator. The M48T58/Y is shipped from STMicroelectronics with the STOP Bit set to a '1.'
When reset to a '0,' the M48T58/Y oscillator starts within 1 second.
15/31
Clock operations
Table 5.
M48T58, M48T58Y
Register map
Data
Function/Range
Address
D7
D6
1FFFh
D5
D4
D3
10 Years
1FFEh
0
0
1FFDh
BLE
BL
1FFCh
0
FT
1FFBh
0
0
1FFAh
0
1FF9h
ST
1FF8h
W
0
10 M
10 Date
CEB
CB
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
Century/Day
0-1/1-7
Hours
Hours
00-23
Minutes
Minutes
00-59
Seconds
Seconds
00-59
0
Day
Calibration
Control
Keys:
S = SIGN Bit
FT = FREQUENCY TEST Bit
R = READ Bit
W = WRITE Bit
ST = STOP Bit
0 = Must be set to '0'
BLE = Battery Low Enable Bit
BL = Battery Low Bit (Read only)
CEB = Century Enable Bit
CB = Century Bit
Note:
When CEB is set to '1,' CB will toggle from '0' to '1' or from '1' to '0' at the turn of the century
(dependent upon the initial value set).
When CEB is set to '0,' CB will not toggle. The WRITE Bit does not need to be set to write to
CEB.
6.4
Calibrating the Clock
The M48T58/Y is driven by a quartz-controlled oscillator with a nominal frequency of 32,768
Hz. 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 M48T58/Y improves to better than +1/–2 ppm at 25°C.
The oscillation rate of any crystal changes with temperature (see Figure 8 on page 18).
Most clock chips compensate for crystal frequency and temperature shift error with
cumbersome “trim” capacitors. The M48T58/Y 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 18. The number of times pulses
are blanked (subtracted, negative calibration) or split (added, positive calibration) depends
upon the value loaded into the five calibration bits 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 (D4-D0) in the Control Register
1FF8h. These bits can be set to represent any value between 0 and 31 in binary form. Bit
16/31
M48T58, M48T58Y
Clock operations
D5 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 32,768 Hz, 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 M48T58/Y 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 some test equipment. When the Frequency Test (FT) Bit (D6 in the Day Register) is set to
a '1,' and D7 of the Seconds Register is a '0' (Oscillator Running), The Frequency Test (Pin
1) will toggle at 512Hz. 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.
The Frequency Test pin is an open drain output which requires a pull-up resistor for proper
operation. A 500-10kΩ resistor is recommended in order to control the rise time.
For more information on calibration, see Application Note AN934, “TIMEKEEPER®
Calibration.”
17/31
Clock operations
Figure 8.
M48T58, M48T58Y
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
6.5
Battery low flag
The M48T58/Y automatically performs periodic battery voltage monitoring upon power-up.
The Battery Low flag (BL), Bit D6 of the flags Register 1FFDh, will be asserted high if the
internal or SNAPHAT® battery is found to be less than approximately 2.5V and the Battery
Low Enable (BLE) Bit has been previously set to '1.' The BL flag will remain active until
completion of battery replacement and subsequent battery low monitoring tests.
If a battery low is generated during a power-up sequence, this indicates that the battery
voltage is below 2.5V (approximately), which may be insufficient to maintain data integrity.
Data should be considered suspect and verified as correct. A fresh battery should be
installed.
The SNAPHAT top may be replaced while VCC is applied to the device.
18/31
M48T58, M48T58Y
Clock operations
Note:
This will cause the clock to lose time during the interval the SNAPHAT battery/crystal top is
disconnected.
Note:
Battery monitoring is a useful technique only when performed periodically. The M48T58/Y
only monitors the battery when a nominal VCC is applied to the device. Thus applications
which require extensive durations in the battery back-up mode should be powered-up
periodically (at least once every few months) in order for this technique to be beneficial.
Additionally, if a battery low is indicated, data integrity should be verified upon power-up via
a checksum or other technique.
6.6
Century bit
Bit D5 and D4 of Clock Register 1FFCh contain the CENTURY ENABLE Bit (CEB) and the
CENTURY Bit (CB). Setting CEB to a '1' will cause CB to toggle, either from a '0' to '1' or
from '1' to '0' at the turn of the century (depending upon its initial state). If CEB is set to a '0,'
CB will not toggle.
Note:
The WRITE Bit must be set in order to write to the CENTURY Bit.
6.7
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 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
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
19/31
Maximum rating
7
M48T58, M48T58Y
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
Ambient Operating Temperature
Storage Temperature (VCC Off, Oscillator Off)
Lead Solder Temperature for 10 seconds
Value
Unit
0 to 70
°C
–40 to 85
°C
260
°C
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.
20/31
M48T58, M48T58Y
8
DC and AC parameters
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 Table 7.
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
M48T58
M48T58Y
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 measurement load circuit
5V
1.9kΩ
DEVICE
UNDER
TEST
OUT
1kΩ
CL = 100pF or 5pF
CL includes JIG capacitance
Table 8.
Capacitance
Symbol
Parameter(1)(2)
CIN
COUT
AI01030
(3)
Min
Max
Unit
Input Capacitance
10
pF
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.
21/31
DC and AC parameters
Table 9.
M48T58, M48T58Y
DC characteristics
Symbol
M48T58
Test condition(1)
Parameter
Unit
Min
ILI
ILO(2)
Input Leakage Current
Output Leakage Current
M48T58Y
Max
Min
Max
0V ≤ VIN ≤ VCC
±1
±1
µA
0V ≤ VOUT ≤ VCC
±1
±1
µA
Outputs open
50
50
mA
ICC
Supply Current
ICC1
Supply Current (Standby)
TTL
E1 = VIH
E2 = VIO
3
3
mA
ICC2
Supply Current (Standby)
CMOS
E1 = VCC – 0.2V
E2 = VSS + 0.2V
3
3
mA
VIL
Input Low Voltage
–0.3
0.8
–0.3
0.8
V
VIH
Input High Voltage
2.2
VCC + 0.3
2.2
VCC + 0.3
V
VOL
VOH
Output Low Voltage
Output Low Voltage
(FT)(3)
Output High Voltage
IOL = 2.1mA
0.4
0.4
IOL = 10mA
0.4
0.4
IOH = –1mA
2.4
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. The FT pin is Open Drain.
Figure 12. Power down/up mode AC waveforms
VCC
VPFD (max)
VPFD (min)
VSO
tF
tR
tFB
INPUTS
tRB
tDR
tPD
RECOGNIZED
trec
DON'T CARE
RECOGNIZED
HIGH-Z
OUTPUTS
VALID
(PER CONTROL INPUT)
VALID
(PER CONTROL INPUT)
AI01168C
22/31
V
M48T58, M48T58Y
Table 10.
DC and AC parameters
Power down/up AC characteristics
Parameter(1)
Symbol
Min
tPD
E1 or W at VIH or E2 at VIL before Power Down
tF(2)
VPFD (max) to VPFD (min) VCC Fall Time
tFB(3)
VPFD (min) to VSS VCC Fall Time
Max
Unit
0
µs
300
µs
M48T58
10
µs
M48T58Y
10
µs
tR
VPFD (min) to VPFD (max) VCC Rise Time
10
µs
tRB
VSS to VPFD (min) VCC Rise Time
1
µs
trec
VPFD (max) to Inputs Recognized
40
200
ms
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.
Power down/up trip points DC characteristics
Parameter(1)(2)
Symbol
Min
Typ
Max
Unit
M48T58
4.5
4.6
4.75
V
M48T58Y
4.2
4.35
4.5
V
VPFD
Power-fail Deselect Voltage
VSO
Battery Back-up Switchover Voltage
tDR(3)
Expected Data Retention Time
3.0
7
V
YEARS
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. All voltages referenced to VSS.
3. At 25°C, VCC = 0V.
23/31
Package mechanical data
9
M48T58, M48T58Y
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
24/31
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
M48T58, M48T58Y
Package mechanical data
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 small outline, 4-socket battery SNAPHAT, package
mech. data
mm
inches
Symb
Typ
Min
A
Max
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
1.27
0.050
28
0.10
0.004
25/31
Package mechanical data
M48T58, M48T58Y
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
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
26/31
Max
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
M48T58, M48T58Y
Package mechanical data
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
Max
Typ
Min
10.54
Max
0.415
A1
8.00
8.51
0.315
0.335
A2
7.24
8.00
0.285
0.315
A3
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
0.710
eB
3.20
3.61
0.126
0.142
L
2.03
2.29
0.080
0.090
27/31
Part numbering
10
M48T58, M48T58Y
Part numbering
Table 16.
Ordering information scheme
Example:
M48T
58
–70
MH
1
E
Device type
M48T
Supply voltage and write protect voltage
58(1) = VCC = 4.75 to 5.5V; VPFD = 4.5 to 4.75V
58Y = VCC = 4.5 to 5.5V; VPFD = 4.2 to 4.5V
Speed
–70 = 70ns
Package
PC = PCDIP28
MH(2) = SOH28
Temperature range
1 = 0 to 70°C
Shipping method
For SOH28:
blank = Tubes (Not for New Design - Use E)
E = Lead-free Package (ECOPACK), Tubes
F = Lead-free Package (ECOPACK), Tape & Reel
TR = Tape & Reel (Not for New Design - Use F)
For PCDIP28:
blank = Tubes
1. The M48T58 part is offered with the PCDIP28 (e.g., CAPHAT™) package only.
2. The SOIC package (SOH28) requires the SNAPHAT® battery package which is ordered separately under
the part number “M4TXX-BR12SH” in plastic tube or “M4TXX-BR12SHTR” in Tape & Reel form (see
Table 17).
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.
28/31
M48T58, M48T58Y
Table 17.
Part numbering
SNAPHAT battery table
Part Number
Description
Package
M4T28-BR12SH
Lithium Battery (48mAh) SNAPHAT
SH
M4T32-BR12SH
Lithium Battery (120mAh) SNAPHAT
SH
29/31
Revision history
11
M48T58, M48T58Y
Revision history
Table 18.
30/31
Document revision history
Date
Revision
Changes
Jul-1999
1.0
First Issue
27-Jul-2000
1.1
Century Bit and Battery Low Flag Paragraphs added; Power Down/Up
AC Characteristics Table and Waveforms changed (Table 10, Figure 12)
04-Jun-2001
2.0
Reformatted; temperature information added (Table 9, 3, 4, 10, 11)
31-Jul-2001
2.1
Formatting changes from recent document review findings
20-May-2002
2.2
Modify reflow time and temperature footnotes (Table 6)
01-Apr-2003
3.0
v2.2 template applied; test condition updated (Table 11)
17-Jul-2003
3.1
Update “Battery Low Flag” information
02-Apr-2004
4.0
Reformatted; update Lead-free packaging information (Table 6, 16)
30-Aug-2007
5.0
Reformatted; added lead-free second level interconnect information to
cover page and Section 9: Package mechanical data; updated Table 9.
M48T58, M48T58Y
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31/31