STM708T/S/R STMicroelectronics, STM708T/S/R Datasheet - Page 12

• Manufacturer Part Number: STM708T/S/R
• Description: 3V Supervisor
• Manufacturer: STMicroelectronics

Specifications of STM708T/S/R

• Stm706/708 T: 3.00 V ≤ VRST≤ 3.15 V S
• Operating Temperature: –40 °C to 85 °C (industrial grade)

Operation
3.5
3.6
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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
the V
V
processor drops below the minimum operating voltage.
If the comparator is unused, PFI should be connected to V
PFO may be connected to MR on the STM70x so that a low voltage on PFI will generate
a reset output.
Ensuring a valid reset output down to V
When V
becomes essentially an open circuit. If a high value pulldown resistor is added to the RST
pin, the output will be held low during this condition. A resistor value of approximately
100 k will be large enough to not load the output under operating conditions, but still
sufficient to pull RST to ground during this low voltage condition (see
Figure 10. Reset output valid to ground circuit
PFI
Figure
several milliseconds before the regulated V
RST
CC
CC
regulator. The voltage divider can be set up such that the voltage at PFI falls below
comparator). If PFI is less than the power-fail threshold (V
falls below 1 V, the state of the RST output can no longer be guaranteed, and
9) to either the unregulated DC input (if it is available) or the regulated output of
Doc ID 10518 Rev 11
STM70x
RST
CC
STM706T/S/R, STM706P, STM708T/S/R
input to the STM70x or the micro-
SS
R1
CC
and PFO left unconnected.
= 0 V
PFI
Figure
), the power-fail
10).
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