MAX6443 MAXIM [Maxim Integrated Products], MAX6443 Datasheet - Page 7

• Manufacturer Part Number: MAX6443
• Description: ?P Reset Circuits with Long Manual Reset Setup Period
• Manufacturer: MAXIM [Maxim Integrated Products]

To minimize data loss and speed system recovery,
many applications interrupt the processor or reset only
portions of the system before a processor hard reset is
asserted. The extended setup time of the MAX6443–
MAX6452 manual reset inputs allows the same push-
button (connected to both the processor interrupt and
the extended MR1 input, as shown in Figure 6) to con-
trol both the interrupt and hard reset functions. If the
pushbutton is closed for less than 6.72s, the processor
is only interrupted. If the system still does not respond
properly, the pushbutton (or two buttons for the dual
manual reset) can be closed for the full extended setup
period to hard reset the processor. If desired, connect
an LED to the RESET output to blink off (or on) for the
reset timeout period to signify when the pushbutton is
Figure 3. MAX6447/MAX6448/MAX6451/MAX6452 MR2
Assertion DebouncingTiming Diagram
Figure 5. Calculating the Monitored Threshold Voltages
RESET
MR2
V
MON_TH
R2
R1
COUNTER RESET
V
MON_TH
= 0.63 x (R1 + R2) / R2
t < 210ms
µP Reset Circuits with Long Manual Reset
Applications Information
_______________________________________________________________________________________
RSTIN
GND
MAX6449
MAX6451
Interrupt Before Reset
t = 210ms
RESET
V
CC
V
CC
closed long enough for a hard reset (the same LED
might be used as the front-panel power-on display).
The MAX6447/MAX6448/MAX6451/MAX6452 dual manu-
al resets are useful in applications in which both an
extended and immediate setup periods are needed.
Figure 7 illustrates the insertion and removal of a smart
card. MR1 monitors a front-panel pushbutton. When
closed for 6.72s, RESET one-shot pulses low for 140ms
min. Because MR1 is internally pulled to V
50kΩ resistor, the front-panel switch can be connected to
Figure 4. MAX6447/MAX6448/MAX6451/MAX6452 MR2
Deassertion Debouncing Timing Diagram
Figure 6. Interrupt Before Reset Application Circuit
RESET
MR2
+3.3V
V
GND
POSITIVE EDGE
CC
TIMEOUT PERIOD
MAX6443
210ms
Smart Card Insertion/Removal
RESET
MR1
Setup Period
LED
DEBOUNCING PERIOD
ASSERTED
NO RESET
OUTPUT
210ms
PUSHBUTTON SWITCH:
CLOSE FOR < 4.48s
FOR SYSTEM INTERRUPT;
CLOSE FOR > 6.72s FOR
SYSTEM RESET
RESET
NMI
V
µ
CC
CC
P
through a
7