MAX6324HUT44-T Maxim Integrated, MAX6324HUT44-T Datasheet - Page 9

• Manufacturer Part Number: MAX6324HUT44-T
• Description: Supervisory Circuits
• Manufacturer: Maxim Integrated
• Series: MAX6323, MAX6324r

Specifications of MAX6324HUT44-T

• Number Of Voltages Monitored: 1
• Monitored Voltage: 2.5 V, 3 V, 3.3 V, 5 V
• Undervoltage Threshold: 4.25 V
• Overvoltage Threshold: 4.5 V
• Output Type: Active Low, Open Drain
• Manual Reset: Resettable
• Watchdog: Watchdog
• Battery Backup Switching: No Backup
• Power-up Reset Delay (typ): 280 ms
• Supply Voltage - Max: 5.5 V
• Maximum Operating Temperature: + 125 C
• Mounting Style: SMD/SMT
• Package / Case: SOT-23
• Chip Enable Signals: No
• Maximum Power Dissipation: 696 mW
• Minimum Operating Temperature: - 40 C
• Power Fail Detection: No
• Supply Current (typ): 27 uA
• Supply Voltage - Min: 1.2 V

Since the RESET output on the MAX6324 is open-drain,
this device easily interfaces with µPs that have bidirec-
tional reset pins, such as the Motorola 68HC11.
Connecting the µP supervisor’s RESET output directly
to the microcontroller’s (µC’s) RESET pin with a single
pullup resistor allows either device to assert reset
(Figure 7).
Generally, the pullup resistor connected to the
MAX6324 will connect to the supply voltage that is
being monitored at the IC’s V
systems may use the open-drain output to level-shift
from the monitored supply to reset circuitry powered by
some other supply (Figure 8). Keep in mind that as the
MAX6324’s V
IC’s ability to sink current at RESET. Also, with any pull-
up resistor, RESET will be pulled high as V
toward 0. The voltage where this occurs depends on
the pullup resistor value and the voltage to which it is
connected.
To help the watchdog timer monitor software execution
more closely, set and reset the watchdog input at dif-
ferent points in the program, rather than “pulsing” the
watchdog input high-low-high or low-high-low. This
technique avoids a “stuck” loop in which the watchdog
Figure 6. RESET Valid to V
MAX6324 Open-Drain RESET Output
Watchdog Software Considerations
Allows Use with Multiple Supplies
CC
Bidirectional Reset Pins
decreases below
_______________________________________________________________________________________
Interfacing to µPs with
µP Supervisory Circuits with Windowed
MAX6323
(Min/Max) Watchdog and Manual Reset
CC
GND
V
V
CC
CC
= Ground Circuit
RESET
CC
pin. However, some
+
1.2V, so does the
R1
100k
CC
decays
time would continue to be reset within the loop, keeping
the watchdog from timing out.
Figure 9 shows an example of a flow diagram where
the I/O driving the watchdog input is set high at the
beginning of the program, set low at the beginning of
every subroutine or loop, then set high again when the
program returns to the beginning. If the program should
“hang” in any subroutine, the problem would be quickly
corrected, since the I/O is continually set low and the
watchdog time is allowed to time out, causing a reset or
interrupt to be issued.
Figure 7. Interfacing to µPs with Bidirectional Reset Pins
Figure 8. MAX6324 Open-Drain RESET Output Allows Use with
Multiple Supplies
V
CC
MAX6324
+3.3V
V
GND
CC
MAX6324
GND
V
CC
RESET
RESET
R
PULLUP
RESET
INPUT
RESET
INPUT
5V SYSTEM
+5.0V
GND
V
CC
GND
V
µP
CC
9