STM1404ARMBQ6F STMICROELECTRONICS [STMicroelectronics], STM1404ARMBQ6F Datasheet - Page 16

• Manufacturer Part Number: STM1404ARMBQ6F
• Description: 3 V FIPS-140 security supervisor with battery switchover
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

Operation
3.5
16/36
Figure 9.
Negative-going V
The STM1404 devices are relatively immune to negative-going V
Figure 23 on page 22
+ 0.3 V and ending below the reset threshold by the magnitude indicated (comparator
overdrive). The graph indicates the maximum pulse width a negative V
without causing a reset pulse. As the magnitude of the transient increases (further below the
threshold), the maximum allowable pulse width decreases. Any combination of duration and
overdrive which lies under the curve will NOT generate a reset signal. Typically, a V
transient that goes 100 mV below the reset threshold and lasts 40 µs or less will not cause a
reset pulse. A 0.1 µF bypass capacitor mounted as close as possible to the V
provides additional transient immunity (see
In addition to transients that are caused by normal SRAM operation, power cycling can
generate negative voltage spikes on V
one volt. These negative spikes can cause data corruption in the SRAM while in battery
backup mode. To protect from these voltage spikes, STMicroelectronics recommends
connecting a schottky diode from V
Schottky diode 1N5817 is recommended for through hole and MBRS120T3 is
recommended for surface mount.
Figure 10. Supply voltage protection
PFO
V CC
V RST
V SW (2.4V)
RST
Power-fail comparator waveform
PFO follows PFI
was generated using a negative pulse applied to V
CC
V CC
transients and undershoot
0.1μF
CC
CC
to V
that drive it to values below V
SS
Figure
(cathode connected to V
10).
V CC
V SS
DEVICE
AI02169
CC
PFO follows PFI
transients (glitches).
trec
CC
CC
SS
CC
AI08861a
transient can have
, anode to V
by as much as
, starting at V
CC
pin
STM1404
CC
SS
).
RST