STM818L/M STMicroelectronics, STM818L/M Datasheet - Page 14

• Manufacturer Part Number: STM818L/M
• Description: 5V Supervisor
• Manufacturer: STMicroelectronics

Specifications of STM818L/M

• Operating Temperature: –40 °C to +85 °C (industrial grade)

Operation
2.4
Note:
Note:
14/43
Backup battery switchover
In the event of a power failure, it may be necessary to preserve the contents of external
SRAM through V
automatically switch the SRAM to the backup supply when V
When the battery is first connected without V
immediately provide backup battery voltage on V
switchover operate as described below. This mode allows a battery to be attached during
manufacturing but not used until after the system has been activated for the first time. As a
result, no battery power is consumed by the device during storage and shipment. For the
STM81x devices, the battery freshness seal can be initiated again by following the
procedure outlined in
V
Whenever V
100
be powered by V
battery life.
Assuming V
before V
external SRAMs. When V
point. V
The backup battery may be removed while V
decoupled (0.1 µF typ), without danger of triggering a reset.
Table 4.
OUT
to V
switch. V
OUT
OUT
E
V
V
PFO
WDI
RST
RST
V
CC
PFI
MR
OUT
CON
BAT
E
CC
is connected to V
BAT
CC
gets too close to the 2.0 V minimum required to reliably retain data in most
I/O status in battery backup
.
falls below the switchover voltage, V
SO
> 2.0 V, switchover at V
OUT
CC
is the lesser of V
for as long as possible before switching over thereby maximizing the
. With a backup battery installed with voltage V
Section
Connected to V
Disconnected from V
Disabled
Logic low
High impedance
Logic high
Watchdog timer is disabled
Disabled
Logic low
Logic high
Connected to V
CC
recovers, hysteresis is used to avoid oscillation around the V
CC
Doc ID 10522 Rev 10
2.12. If the backup battery is not used, connect both V
through a 3
BAT
OUT
BAT
SO
and V
through internal switch
OUT
ensures that battery backup mode is entered
STM690A/692A/703/704/802/805/817/818/819
CC
CC
RST
PMOS power switch.
is valid, assuming V
power applied, the device does not
OUT
. Choosing the lesser allows the device to
SO
. Only after V
, V
OUT
CC
is connected to V
falls.
CC
BAT
BAT
exceeds V
, the devices
is adequately
BAT
RST
through a
BAT
will the
and
SO