STM1001L STMICROELECTRONICS [STMicroelectronics], STM1001L Datasheet - Page 4

• Manufacturer Part Number: STM1001L
• Description: Reset Circuit
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

STM1001
OPERATION
Reset Output
The STM1001 MICROPROCESSOR RESET
CIRCUIT asserts a reset signal to the MCU when-
ever V
RST is guaranteed valid down to V
70°C).
During power-up, once V
threshold an internal timer keeps RST low for the
reset time-out period, t
returns high.
If V
low. Each time RST is asserted, it stays low for at
least the reset time-out period. Any time V
below the reset threshold, the internal timer clears.
The reset timer starts when V
reset threshold. The active-low reset (RST) is an
open drain output.
Negative-Going V
The STM1001 is relatively immune to negative-go-
ing V
shows typical transient duration versus reset com-
parator overdrive (for which the STM1001 will
NOT generate a reset pulse). The graph was gen-
erated using a negative pulse applied to V
starting at 0.5V above the actual reset threshold
4/13
CC
CC
CC
drops below the reset threshold, RST goes
transients (glitches).
goes below the reset threshold (V
CC
Transients
rec
. After this interval, RST
CC
CC
exceeds the reset
Figure 11., page 7
returns above the
CC
= 1V (0° to
CC
RST
goes
CC
).
,
and ending below it by the magnitude indicated
(comparator overdrive). The graph indicates the
maximum pulse width a negative V
can have without causing a reset pulse. As the
magnitude of the transient increases (further be-
low the threshold), the maximum allowable pulse
width decreases. Any combination of duration and
overdrive which lies under the curve will NOT gen-
erate a reset signal. Typically, a V
goes 100mV below the reset threshold and lasts
20µs or less will not cause a reset pulse. A 0.1µF
bypass capacitor mounted as close as possible to
the V
Valid /RST Output Down to V
When V
er sinks current, but becomes an open circuit. In
most systems this is not a problem, as most MCUs
do not operate below 1V. However, in applications
where RST output must be valid down to 0V, a
pull-down resistor may be added to hold the RST
output low. This resistor must be large enough to
not load the RST output, and still be small enough
to pull the output to ground. A 100K
recommended.
CC
CC
pin provides additional transient immunity.
falls below 1V, the RST output no long-
CC
CC
= 0V
transient that
CC
resistor is
transient