STM708 STMicroelectronics, STM708 Datasheet - Page 12

• Manufacturer Part Number: STM708
• Description: 5V Supervisor
• Manufacturer: STMicroelectronics

Specifications of STM708

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

Operation
3.4
3.5
3.6
12/33
Watchdog output (STM705/706/813L)
When V
not yet timed out. However, unlike the reset output, WDO goes high as soon as V
exceeds the reset threshold. WDO may be used to generate a reset pulse by connecting it
to the MR input.
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
or the microprocessor 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 STM703/704/818 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
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
will be large enough to not load the output under operating conditions, but still
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
drops below the reset threshold, WDO will go low even if the watchdog timer has
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 10520 Rev 9
STMXXX
STM705, STM706, STM707, STM708, STM813L
RST
CC
input to the STM705/706/707/708/ 813L
SS
CC
and PFO left unconnected.
R1
= 0 V
PFI
Figure
), the power-fail
10).
CC
AI08835