MAX821LUS-T Maxim Integrated, MAX821LUS-T Datasheet - Page 6

• Manufacturer Part Number: MAX821LUS-T
• Description: Supervisory Circuits
• Manufacturer: Maxim Integrated
• Series: MAX821, MAX821L, MAX821M, MAX821P, MAX821R, MAX821S, MAX821T, MAX821U, MAX822, MAX822L, MAX822M, MAX822R, MAX822S, MAX822Tr

Specifications of MAX821LUS-T

• Number Of Voltages Monitored: 1
• Monitored Voltage: 3 V to 5 V
• Undervoltage Threshold: 4.56 V
• Overvoltage Threshold: 4.7 V
• Output Type: Active Low, Push-Pull
• Manual Reset: Not Resettable
• Watchdog: No Watchdog
• Battery Backup Switching: No Backup
• Power-up Reset Delay (typ): 200 ms
• Supply Voltage - Max: 5.5 V
• Maximum Operating Temperature: + 125 C
• Package / Case: SOT-143
• Chip Enable Signals: No
• Maximum Power Dissipation: 320 mW
• Minimum Operating Temperature: - 40 C
• Power Fail Detection: No
• Supply Current (typ): 7 uA
• Supply Voltage - Min: 1 V

When V
no longer sinks current—it becomes an open circuit.
Therefore, high-impedance CMOS logic inputs con-
nected to the RESET output can drift to undetermined
voltages. This presents no problem in most applica-
tions, since most µP and other circuitry is inoperative
with V
RESET output must be valid down to 0V, adding a pull-
down resistor to the RESET pin will cause any stray
leakage currents to flow to ground, holding RESET low
(Figure 2a). R1’s value is not critical; 100kΩ is large
enough not to load RESET, and small enough to pull
RESET to ground.
A 100kΩ pull-up resistor to V
for the MAX822 if RESET is required to remain valid for
V
µPs with bidirectional reset pins (such as the Motorola
68HC11 series) can contend with the MAX821 reset
output. For example, if the MAX821 RESET output is
asserted high and the µP wants to pull it low, indetermi-
nate logic levels may result. To correct such cases,
connect a 4.7kΩ resistor between the MAX821 RESET
output and the µP reset I/O (Figure 3). Buffer the reset
output to other system components.
TRANSISTOR COUNT: 492
4-Pin µP Voltage Monitors with Pin-Selectable
Power-On Reset Timeout Delay
6
___________________Chip Information
CC
_______________________________________________________________________________________
< 1V (Figure 2b).
CC
CC
below 1V. However, in applications where the
falls below 1V, the MAX821 RESET output
Ensuring a Valid
Bidirectional Reset Pins
Interfacing to µPs with
CC
Down to V
is also recommended
RESET Output
CC
= 0V
Figure 2. RESET/ RESET Valid to V
Figure 3. Interfacing to µPs with Bidirectional Reset I/O
a)
MAX821
GND
V
CC
MAX821
RESET
GND
V
V
CC
CC
RESET
4.7k
R1
RESET
CC
BUFFER
GND
b)
V
µP
CC
= Ground Circuit
MAX822
GND
V
V
CC
CC
BUFFERED RESET
TO OTHER SYSTEM
COMPONENTS
RESET
R1