ADM811LART-REEL-7 AD [Analog Devices], ADM811LART-REEL-7 Datasheet - Page 5

• Manufacturer Part Number: ADM811LART-REEL-7
• Description: Microprocessors Supervisory Circuit in 4-Lead SOT-143
• Manufacturer: AD [Analog Devices]

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CIRCUIT INFORMATION
RESET THRESHOLDS
The reset output provides a RESET (for the ADM811) or a
RESET (for the ADM812) output to the microprocessor when-
ever the V
threshold is dependant on whether a L, M, T, S or R suffix is
used. Please refer to Table I.
Parts in bold type are ex-stock, please contact factory for availability.
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 inter-
ruption occurs, the reset output is similarly activated and re-
mains active for 240 ms (typical) after the supply recovers. 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 re-
mains valid (low) with V
microprocessor is held in a stable shutdown condition as the
supply falls and also ensures that no spurious activity can occur
via the P as it powers up.
MANUAL RESET
The ADM811/ADM812 is 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 may pickup noise).
The Manual Reset input is guaranteed to ignore logically valid
inputs which are faster than 100 ns and accept inputs longer in
duration than 10 s.
CC
Model
ADM811LART
ADM811MART
ADM811TART
ADM811-3TART
ADM811SART
ADM811RART
ADM812LART
ADM812MART
ADM812TART
ADM812SART
ADM812RART
input is below the reset threshold. The actual reset
Table I. Reset Threshold Options
CC
CC
as low as 1 V. This ensures that the
rises above the reset threshold, an
RESET
Threshold
4.63 V
4.38 V
3.08 V
3.08 V
2.93 V
2.63 V
4.63 V
4.38 V
3.08 V
2.93 V
2.63 V
–5–
GLITCH IMMUNITY
The ADM811/ADM812 contain internal filtering circuitry
providing glitch immunity from fast transient glitches on the
power supply line.
INTERFACING TO OTHER DEVICES
Output
The ADM811/ADM812 series is designed to integrate with
as many devices as possible. One feature of the ADM811/
ADM812 is the reset output, which is directly proportional to
V
enables the part to be used in both 3 V and 5 V or any nominal
voltage within the minimum and maximum specifications for V
THE BENEFITS OF A VERY ACCURATE RESET
THRESHOLD
Because the ADM811/ADM812 series can operate effectively
even when there are large degradations of the supply voltages,
the possibility of a malfunction during a power failure is greatly
reduced. Another advantage of the ADM811/ADM812 series is
its very accurate internal voltage reference circuit. Combined,
these benefits produce an exceptionally reliable Microprocessor
Supervisory Circuit.
ENSURING A VALID RESET OUTPUT DOWN TO
V
When V
current. Therefore, a high impedance CMOS logic input con-
nected to RESET may drift to undetermined logic levels. To
eliminate this problem a 100 k resistor should be connected
from RESET to ground.
CC
CC
= 0 V
(this is guaranteed only while V
Figure 9. Ensuring a Valid RESET Output Down to
V
RESET
CC
V
CC
CC
= 0 V
V
t
falls below 0.8 V, ADM811s RESET no longer sinks
1
REF
= RESET TIME = 240ms TYPICAL
Figure 8. Power Fail RESET Timing
= RESET VOLTAGE THRESHOLD
V
REF
t
1
ADM811
GND
V
V
V
CC
CC
REF
RESET
ADM811/ADM812
CC
V
REF
is greater than 1 V). This
t
1
V
REF
CC
.