ADM1232A
Rev. A | Page 6 of 8
CIRCUIT INFORMATION
PB RESET
Table 4. Strobe Timeout Settings
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 ADM1232A
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.
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
STROBE TIMEOUT PERIOD
STROBE
STROBE
PULSE WIDTH
00061-006
MICROPROCESSOR
GND TOLERANCE
RESET
STROBE
RESETPB RESET
I/O
ADM1232A
CC
V
CC
TD
00061-004
Figure 6.
STROBE
Parameters
V
CC
RESET
5V
4.5V (5% TRIP POINT)
RESET OUTPUT DELAY
HEN V
CC
IS FALLING
RESET OUTPUT DELAY
WHEN V
CC
IS RISING
5V
4.25V (10% TRIP POINT)
RESET
00061-007
Figure 4. Typical Push-Button Reset Application
RESET
RESET
PB RESET
V
IL
RESET ACTIVE
TIME
PB RESET
DELAY
PB RESET TIME
V
IH
00061-005
Figure 7. Reset Output Delay
TOLERANCE
The TOLERANCE input is used to determine the level V
CC
can vary below 5 V without the ADM1232A asserting a reset.
Connecting TOLERANCE to ground selects a −5% tolerance
level and causes the ADM1232A 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 and causes the ADM1232A to
generate a reset if V
CC
falls below 4.5 V. Check the parameters
for the V
CC
trip point in the Specifications section for more
information.
Figure 5.
PB RESET
STROBE TIMEOUT SELECTION
TD or time delay set is used to set the strobe timeout period.
The strobe timeout period is defined as being 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 6
Table 4
RESET AND RESET OUTPUTS
While RESET is capable of sourcing and sinking current,
RESET
is an open drain MOSFET which sinks current only.
Therefore, it is necessary to pull
RESET
output high.
