3 V, Voltage Monitoring
Microprocessor Supervisory Circuits
ADM706P/ADM706R/ADM706S/ADM706T, ADM708R/ADM708S/ADM708T
FEATURES
Precision supply voltage monitor
2.63 V (ADM706P, ADM706R, ADM708R)
2.93 V (ADM706S, ADM708S)
3.08 V (ADM706T, ADM708T)
100 μA quiescent current
200 ms reset pulse width
Debounced manual reset input (MR)
Independent watchdog timer
1.6 second timeout (ADM706x)
Reset output
Active high (ADM706P)
Active low (ADM706R, ADM706S, ADM706T)
Both active high and active low (ADM708R, ADM708S,
ADM708T)
Voltage monitor for power-fail or low battery warning
Guaranteed RESET valid with V
CC
= 1 V
Superior upgrade for MAX706P/R/S/T, MAX708R/S/T
WATCHDOG
INPUT (WDI)
FUNCTIONAL BLOCK DIAGRAMS
WATCHDOG
TRANSITION
DETECTOR
V
CC
70μA
MR
V
CC
V
REF
*
POWER-FAIL
INPUT (PFI)
1.25V
WATCHDOG
TIMER
WATCHDOG
OUTPUT (WDO)
RESET AND
WATCHDOG
TIMEBASE
RESET
GENERATOR
RESET,
(P = RESET)
ADM706P/ADM706R/
ADM706S/ADM706T
POWER-FAIL
OUTPUT (PFO)
06435-001
* VOLTAGE REFERENCE = 2.63V (P/R), 2.93V (S), 3.08V (T)
Figure 1. ADM706P/ADM706R/ADM706S/ADM706T
V
CC
70μA
MR
RESET
GENERATOR
V
REF
*
POWER-FAIL
INPUT (PFI)
1.25V
* VOLTAGE REFERENCE = 2.63V (R), 2.93V (S), 3.08V (T)
RESET
RESET
APPLICATIONS
Microprocessor systems
Computers
Controllers
Intelligent instruments
Critical microprocessor monitoring
Battery-operated systems
Portable instruments
V
CC
ADM708R/ADM708S/
ADM708T
06435-002
POWER-FAIL
OUTPUT (PFO)
Figure 2. ADM708R/ADM708S/ADM708T
GENERAL DESCRIPTION
The ADM706P/ADM706R/ADM706S/ADM706T and the
ADM708R/ADM708S/ADM708T microprocessor supervisory
circuits are suitable for monitoring either 3 V or 3.3 V power
supplies.
The ADM706P/ADM706R/ADM706S/ADM706T provide
power-supply monitoring circuitry that generate a reset output
during power-up, power-down, and brownout conditions. The
reset output remains operational with V
CC
as low as 1 V.
Independent watchdog monitoring circuitry is also provided.
This is activated if the watchdog input has not been toggled
within 1.6 seconds.
In addition, there is a 1.25 V threshold detector for power-fail
warning, low battery detection, or to monitor an additional power
supply. An active low debounced MR input is also included.
The ADM706R, ADM706S, and ADM706T are identical except
for the reset threshold monitor levels, which are 2.63 V, 2.93 V, and
3.08 V, respectively. The ADM706P is identical to the ADM706R in
that the reset threshold is 2.63 V. It differs only in that it has an
active high reset output.
The ADM708R/ADM708S/ADM708T provide similar functio-
nality as the ADM706R/ADM706S/ADM706T and only differ
in that a watchdog timer function is not available. Instead, an
active high reset output (RESET) is provided in addition to the
active low (RESET) output.
All parts are available in narrow 8-lead PDIP and 8-lead SOIC
packages.
Rev. C
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