STM818L/M STMicroelectronics, STM818L/M Datasheet - Page 16

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

Specifications of STM818L/M

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

Operation
Figure 12. Chip-enable waveform
2.8
2.9
16/43
Power-fail input/output (NOT available on STM818)
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
of the V
below V
STM690A/692A/703/704/802/805/817/818/819 Supervisor or before the microprocessor
drops below the minimum operating voltage. This provides several milliseconds of advanced
warning that power is about to fail.
During battery backup, the power-fail comparator turns off and PFO goes (or remains) low
(see
When power returns, PFO is forced high (STM817/819 only), irrespective of V
WRITE protect time (t
PFO follows PFI. If the comparator is unused, PFI should be connected to V
unconnected. PFO may be connected to MR on the STM703/704/818 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.
E
RST
E
V
CC
CON
Figure
Figure 13
RST
CC
PFI
comparator). If PFI is less than the power-fail threshold (V
V
regulator. The voltage divider can be set up such that the voltage at PFI falls
several milliseconds before the regulated V
RST
12) to either the unregulated DC input (if it is available) or the regulated output
V
BAT
below and
X X
t rec
rec
CC
). At the end of this time, the power-fail comparator is enabled and
Figure
and V
Doc ID 10522 Rev 10
15µs
14). This occurs after V
BAT
pins to ground by placing 0.1 µF capacitors as close to
t rec
XX
STM690A/692A/703/704/802/805/817/818/819
CC
CC
input to the
drops below 2.4 V (or V
OUT
PFI
), the Power-Fail
to ground -
SS
PFI
and PFO left
for the
AI08803b
SO
).