ADM812 Analog Devices, ADM812 Datasheet - Page 7
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ADM812
Manufacturer Part Number
ADM812
Description
Microprocessors Supervisory Circuit in 4-Lead SOT-143, Logic High RESET Output
Manufacturer
Analog Devices
Datasheet
1.ADM811.pdf
(12 pages)
Specifications of ADM812
# Of Monitored Voltages
1
Backup-battery Switch
No
Manual Reset Capability
Yes
Package
SOT
Reset Threshold Summary
6 Options--2.32 to 4.63V
Reset Output-stage
Active-High/Push-Pull
Min Reset Timeout (ms)
140
Watchdog Timer
No
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CIRCUIT INFORMATION
RESET THRESHOLDS
A reset output is provided to the microprocessor whenever the
V
depends on whether an L, M, T, S, R, or Z suffix is used (see
Table 4).
Table 4. Reset Threshold Options
Model
ADM811LART
ADM811MART
ADM811TART
ADM811-3TART
ADM811SART
ADM811RART
ADM811ZART
ADM812LART
ADM812MART
ADM812TART
ADM812SART
ADM812RART
ADM812ZART
RESET OUTPUT
On power-up and after V
internal timer holds the reset output active for 240 ms (typical).
This is intended as a power-on reset signal for the processor. It
allows time for both the power supply and the microprocessor
to stabilize after power-up. If a power supply brownout or
interruption occurs, the reset output is similarly activated and
remains active for 240 ms (typical) after the supply recovers.
CC
input is below the reset threshold. The actual reset threshold
CC
rises above the reset threshold, an
Reset Threshold (V)
4.63
4.38
3.08
3.08
2.93
2.63
2.32
4.63
4.38
3.08
2.93
2.63
2.32
Rev. F | Page 7 of 12
This allows time for the power supply and microprocessor to
stabilize.
The ADM811 provides an active low reset output ( RESET )
while the ADM812 provides an active high output (RESET).
During power-down of the ADM811, the RESET output
remains valid (low) with V
the microprocessor is held in a stable shutdown condition as
the supply falls and also ensures that no spurious activity can
occur via the microprocessor as it powers up.
MANUAL RESET
The ADM811/ADM812 are equipped with a manual reset
input. This input is designed to operate in a noisy environment
where unwanted glitches could be induced. These glitches could
be produced by the bouncing action of a switch contact, or where a
manual reset switch may be located some distance away from
the circuit (the cabling of which can pick up noise).
The manual reset input is guaranteed to ignore logically valid
inputs that are faster than 100 ns and to accept inputs longer in
duration than 10 μs.
GLITCH IMMUNITY
The ADM811/ADM812 contain internal filtering circuitry
providing glitch immunity from fast transient glitches on the
power supply line.
RESET
V
CC
t
V
1
REF
= RESET TIME = 250ms TYPICAL
V
= RESET VOLTAGE THRESHOLD
REF
Figure 10. Power Fall RESET Timing
t
1
V
REF
CC
as low as 1 V. This ensures that
V
ADM811/ADM812
REF
t
1
V
REF