STM704T/S/R STMicroelectronics, STM704T/S/R Datasheet - Page 15

• Manufacturer Part Number: STM704T/S/R
• Description: 3V Supervisor
• Manufacturer: STMicroelectronics

Specifications of STM704T/S/R

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

STM690, STM704, STM795, STM802, STM804, STM805, STM806
2.4
Note:
Note:
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 battery backup 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. If the
backup battery is not used, connect both V
This family of supervisors does not always connect V
V
V
to have a higher voltage than V
Assuming that 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.
CC
BAT
. V
Vccsw
E
V
V
PFO
RST
RST
WDI
(whichever is lower). This is done to allow the backup battery (e.g., a 3.6 V lithium cell)
V
Pin
PFI
MR
OUT
CON
BAT
E
BAT
CC
OUT
OUT
connects to V
is connected to V
gets too close to the 2.0 V minimum required to reliably retain data in most
I/O status in battery backup
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
Logic high (STM795)
BAT
OUT
> 2.0 V, switchover at V
. With a backup battery installed with voltage V
OUT
CC
recovers, hysteresis is used to avoid oscillation around the V
(through a 100
OUT
BAT
CC
Doc ID 10519 Rev 9
CC
through a 3
through internal switch
.
OUT
BAT
SO
CC
CC
ensures that battery backup mode is entered
switch) when V
and V
PMOS power switch.
is valid, assuming V
power applied, the device does not
OUT
Status
. Only after V
OUT
BAT
to V
to V
CC
OUT
CC
CC
.
falls.
is below V
when V
CC
BAT
BAT
exceeds V
, the devices
is adequately
BAT
SW
is greater than
(2.4 V) or
RST
Operation
will the
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SO