M41T315Y*, M41T315V, M41T315W
4/24
SUMMARY DESCRIPTION
The M41T315Y/V/W RTC Supervisor is a combi-
nation of a CMOS TIMEKEEPER
and a nonvola-
tile memory supervisor. Power is constantly
monitored by the memory supervisor. In the event
of power instability or absence, an external battery
maintains the timekeeping operation and provides
power for a CMOS static RAM by switching on and
invoking write protection to prevent data corrup-
tion in the memory and RTC.
The clock keeps track of tenths/hundredths of sec-
onds, seconds, minutes, hours, day, date, month,
and year information. The last day of the month is
automatically adjusted for months with less than
31 days, including leap year correction.
The clock operates in one of two formats:
–
a 12-hour mode with an AM/PM indicator;
or
–
a 24-hour mode
The nonvolatile supervisor supplies all the neces-
sary support circuitry to convert a CMOS RAM to
a nonvolatile memory. The M41T315Y/V/W can
be interfaced with RAM without leaving gaps in
memory.
The M41T315Y/V/W is supplied in a 28-lead SOIC
SNAPHAT
package (which integrates both crys-
tal and battery in a single SNAPHAT top) or a-16
pin SOIC. The 28-pin, 330mil SOIC provides sock-
ets with gold plated contacts at both ends for direct
connection to a separate SNAPHAT housing con-
taining the battery and crystal. The unique design
allows the SNAPHAT battery/crystal 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 sur-
face-mounting. The SNAPHAT housing is also
keyed to prevent reverse insertion.
The 28-pin 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
“M4TXX-BR12SH”
17., page 22
).
Caution:
Do not place the SNAPHAT battery/crys-
tal top in conductive foam, as this will drain the lith-
ium button-cell battery.
(see
Table
Figure 3. Logic Diagram
Note: 1. For 16-pin SOIC only
Table 1. Signal Names
AI03902
D
Q
VCCI
M41T315Y
M41T315V
M41T315W
OE
VSS
CEI
WE
CEO
RST
VCCO
VBAT
XI
XO
(1)
(1)
(1)
XI-XO
32.768 kHz Crystal Connection
D
Data Input
Q
Data Output
RST
Reset Input
CEO
Chip Enable Output
CEI
Chip Enable Input
V
BAT
Battery Input
OE
Output Enable Input
WE
WRITE Enable Input
V
CCO
Switched Supply Voltage Output
V
CCI
Supply Voltage Input
V
SS
Ground
NC
Not Connected Internally
DU
Don’t Use