ADM1232
Rev. C | Page 6 of 12
CIRCUIT INFORMATION
PB RESET STROBE TIMEOUT SELECTION
The
PB RESET
input makes it possible to manually reset a
system using either a standard push-button switch or a logic
low input. An internal debounce circuit provides glitch
immunity when used with a switch, reducing the effects of
glitches on the line. The debounce circuit is guaranteed to cause
the ADM1232 to assert a reset if
PB RESET
is brought low for
more than 20 ms and is guaranteed to ignore low inputs of less
than 1 ms.
TD (time delay) set is used to set the strobe timeout period. The
strobe timeout period is the maximum time between high-to-
low transitions that
STROBE
accepts before a reset is asserted
(see ). The strobe timeout settings are listed in . Figure 8 Table 5
Table 5. Strobe Timeout Settings
Condition Min Typ Max Unit
TD = 0 V 62.5 150 250 ms
TD = Floating 250 600 1000 ms
TD = V
CC
500 1200 2000 ms
MICROPROCESSOR
GND TOLERANCE
RESET
STROBE
RESETPB RESET
I/O
ADM1232
V
CC
V
CC
TD
STROBE
PULSE WIDTH
STROBE TIMEOUT PERIOD
STROBE
07522-008
07522-0
RESET
06
Figure 8.
STROBE
Parameters
Figure 6. Typical Push-Button Reset Application
RESET
PB RESET
V
IL
RESET ACTIVE
TIME
PB RESET
DELAY
PB RESET TIME
V
IH
07
5V
V
CC
RESET
5V
4.5V (5% TRIP POINT)
RESET OUTPUT DELAY
HEN V
CC
IS FALLING
RESET OUTPUT DELAY
WHEN V
CC
IS RISINGW
4.25V (10% TRIP POINT)
RESET
07522-009
Figure 9. Reset Output Delay
07522-0
TOLERANCE
Figure 7.
PB RESET
The TOLERANCE input is used to determine the level at which
V
CC
can vary below 5 V without the ADM1232 asserting a reset.
Connecting TOLERANCE to GND selects a −5% tolerance level
and causes the ADM1232 to generate a reset if V
CC
falls below
4.75 V. If TOLERANCE is connected to V
CC
, a −10% tolerance
level is selected, which causes the ADM1232 to generate a reset
if V
CC
falls below 4.5 V. See the parameters for the V
CC
trip point
in the Specifications section for more information.
RESET AND RESET OUTPUTS
RESET is capable of sourcing and sinking current, whereas
RESET
is an open-drain MOSFET that sinks current only.
Therefore, it is necessary to pull this output high.
