STM1403ARMQ6F STMICROELECTRONICS [STMicroelectronics], STM1403ARMQ6F Datasheet - Page 15

• Manufacturer Part Number: STM1403ARMQ6F
• Description: 3 V FIPS-140 security supervisor with battery switchover
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

STM1403
3.4
3.5
Table 3.
Power-fail input/output
The power-fail input (PFI) is compared to an internal reference voltage (independent from
the V
output (PFO) will go low. This function is intended for use as an undervoltage detector to
signal a failing power supply. Typically PFI is connected through an external voltage divider
(see
regulated output of the V
voltage at PFI falls below V
STM1403 or the microprocessor drops below the minimum operating voltage.
During battery backup, the power-fail comparator is turned off and PFO goes (or remains)
low (see
power returns, the power-fail comparator is enabled and PFO follows PFI. If the comparator
is unused, PFI should be connected to V
connected to MR so that a low voltage on PFI will generate a reset output.
Applications information
These supervisor circuits are not short-circuit protected. Shorting V
excluding power-up transients such as charging a decoupling capacitor - destroys the
device. Decouple both V
the device as possible.
Vccsw
Figure 4 on page
V
V
V
RST
PFO
V
RST
BLD
V
Pin
PFI
MR
OUT
REF
TPU
BAT
CC
Figure 9 on page
comparator). If PFI is less than the power-fail threshold (V
I/O status in battery backup
Connected to V
Disconnected from V
Disabled
Logic low
Disabled
Logic low
Connected to V
Logic high
Pulled to V
Logic high
Connected to V
9) to either the unregulated DC input (if it is available) or the
CC
CC
SS
16). This occurs after V
PFI
and V
regulator. The voltage divider can be set up such that the
below 2.4 V (V
OUT
BAT
BAT
several milliseconds before the regulated V
BAT
through internal switch
through an internal switch
OUT
pins to ground by placing 0.1 µF capacitors as close to
SS
SW
and PFO left unconnected. PFO may be
)
Status
CC
drops below V
OUT
PFI
SW
), the power-fail
(~2.4V). When
to ground -
CC
input to the
Operation
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