M48T35-70MH1 STMICROELECTRONICS [STMicroelectronics], M48T35-70MH1 Datasheet - Page 3

• Manufacturer Part Number: M48T35-70MH1
• Description: 256 Kbit 32Kb x8 TIMEKEEPER SRAM
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

Table 3. Operating Modes
Note: 1. X = V
Figure 3. Block Diagram
nection to a separate SNAPHAT housing contain-
ing 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/crys-
tal packages are shipped separately in plastic anti-
static tubes or in Tape & Reel form.
Deselect
Write
Read
Read
Deselect
Deselect
Mode
2. See Table 7 for details.
CRYSTAL
32,768 Hz
LITHIUM
IH
CELL
or V
IL
V
; V
SO
SO
4.75V to 5.5V
4.5V to 5.5V
to V
= Battery Back-up Switchover Voltage.
V
PFD
V
or
CC
SO
(1)
(min)
OSCILLATOR AND
VOLTAGE SENSE
CLOCK CHAIN
SWITCHING
CIRCUITRY
(2)
AND
V CC
V
V
V
V
E
X
X
IH
IL
IL
IL
POWER
V PFD
V
V
G
X
X
X
X
IH
IL
For the 28 lead SOIC, the battery/crystal package
(i.e.
BR12SH1".
As Figure 3 shows, the static memory array and
the quartz controlled clock oscillator of the
M48T35/35Y 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 ad-
dresses 7FF8h-7FFFh.
SNAPHAT)
V
V
V
W
X
X
X
IH
IH
IL
SRAM ARRAY
SRAM ARRAY
8 x 8 BiPORT
32,760 x 8
V SS
DQ0-DQ7
High Z
High Z
High Z
High Z
D
D
OUT
part
IN
number
M48T35, M48T35Y
Battery Back-up Mode
CMOS Standby
Standby
Power
Active
Active
Active
A0-A14
DQ0-DQ7
E
W
G
is
AI01623
"M4T28-
3/18