MAX802TMJA Maxim Integrated, MAX802TMJA Datasheet - Page 9

• Manufacturer Part Number: MAX802TMJA
• Description: Supervisory Circuits
• Manufacturer: Maxim Integrated
• Series: MAX690R, MAX690S, MAX690T, MAX704R, MAX704S, MAX704T, MAX802, MAX802R, MAX802S, MAX802T, MAX804, MAX804R, MAX804S, MAX804T, MAX805, MAX805R, MAX805S, MAX805T, MAX806, MAX806R, MAX806S, MAX806Tr

Specifications of MAX802TMJA

• Number Of Voltages Monitored: 1
• Monitored Voltage: 4.65 V
• Output Type: Active Low, Push-Pull
• Manual Reset: Not Resettable
• Watchdog: Watchdog
• Battery Backup Switching: Backup
• Supply Voltage - Max: 5.5 V
• Chip Enable Signals: No
• Maximum Power Dissipation: 727 mW
• Power Fail Detection: Yes
• Supply Current (typ): 350 uA
• Supply Voltage - Min: 1 V

Figure 3. Using a SuperCap as a Backup Power Source
Connecting an ordinary signal diode in series with R3,
as shown in Figure 4b, causes the lower trip point (V
to coincide with the trip point without hysteresis (V
so the entire hysteresis window occurs above V
This method provides additional noise margin without
compromising the accuracy of the power-fail threshold
when the monitored voltage is falling. It is useful for
accurately detecting when a voltage falls past a
threshold.
The current through R1 and R2 should be at least 1µA to
ensure that the 25nA (max over extended temperature
range) PFI input current does not shift the trip point. R3
should be larger than 10kΩ so it does not load down the
–
P
These µP supervisors can monitor either positive or
negative supplies using a resistor voltage divider to
PFI.
µP (Figure 5). Connecting
and MAX806 causes reset to assert when the
monitored supply goes out of tolerance. Reset remains
asserted as long as
after
µPs with bidirectional reset pins, such as the Motorola
68HC11 series, can contend with the MAX690_/
MAX704_/MAX802_/MAX806_
—
F
—
a
3.0V/3.3V Microprocessor Supervisory Circuits
O
–
3.0V OR 3.3V
–
P
–
Monitoring an Additional Power Supply
P
—
pin. Capacitor C1 adds additional noise rejection.
—
F
F
—
—
O
O
–
–
1N4148
0.47F
goes high.
can be used to generate an interrupt to the
( ) ARE FOR MAX804T/S/R, MAX805T/S/R ONLY
V
VBATT
with Bidirectional Reset Pins
CC
_______________________________________________________________________________________
–
P
—
F
—
MAX690T/S/R
MAX704T/S/R
MAX802T/S/R
MAX804T/S/R
MAX805T/S/R
MAX806T/S/R
O
–
holds
GND
–
P
—
F
—
O
–
–
R
–
—
M
Interfacing to µPs
to
—
(RESET)
E
—
RESET
R
–
V
S
–
M
—
OUT
—
low, and for 200ms
E
—
R
–
T
–
on the MAX704
output. If, for
TO STATIC
RAM
TO μP
TRIP
TRIP
L
),
)
.
b
example, the
wants to pull it low, indeterminate logic levels may
result. To correct this, connect a 4.7kΩ resistor
between the
Figure 6. Buffer the
components.
While issuing resets to the µP during power-up, power-
down, and brownout conditions, these supervisors are
relatively immune to short-duration negative-going V
transients (glitches). It is usually undesirable to reset
the µP when V
Figure 7 shows maximum transient duration vs. reset-
comparator overdrive, for which reset pulses are not
generated. The graph was produced using negative-
going V
the reset threshold by the magnitude indicated (reset
comparator overdrive). The graph shows the maximum
pulse width a negative-going V
typically have without causing a reset pulse to be
issued. As the amplitude of the transient increases
(i.e., goes farther below the reset threshold), the
maximum allowable pulse width decreases. Typically,
a V
threshold and lasts for 40µs or less will not cause a
reset pulse to be issued.
A 100nF bypass capacitor mounted close to the V
pin provides additional transient immunity.
+5V
CC
1N4148
3.0V OR
0.47F
transient that goes 100mV below the reset
CC
3.3V
pulses, starting at 3.3V and ending below
( ) ARE FOR MAX804T/S/R, MAX805T/S/R ONLY
–
R
—
–
R
CC
—
E
V
VBATT
—
Negative-Going V
E
CC
—
S
—
S
experiences only small glitches.
—
E
—
E
—
T
–
T
MAX690T/S/R
MAX704T/S/R
MAX802T/S/R
MAX804T/S/R
MAX805T/S/R
MAX806T/S/R
–
output and the µP reset I/O, as in
–
R
—
output is driven high and the µP
E
—
GND
S
—
E
—
T
–
(RESET)
output to other system
RESET
V
OUT
CC
CC
transient may
Transients
TO STATIC
RAM
TO μP
CC
CC
9