Low-Voltage, High-Accuracy, Quad-Voltage
µP Supervisory Circuit in SOT Package
nal bandgap reference/comparator voltage. Adjustable
threshold options bypass the internal resistor networks
and connect directly to one of the comparator inputs (an
external resistor-divider network is required for threshold
matching). The MAX6710Q provides a separate unmoni-
tored power-supply input (V
CC
) and three adjustable volt-
age inputs.
Each of the internal comparators has a typical hystere-
sis of 0.3% with respect to its reset threshold. This built-
in hysteresis improves the monitor’s immunity to
ambient noise without significantly reducing threshold
accuracy when an input sits at its specified reset volt-
age. The MAX6710 is also designed to ignore short IN_
transients. See
Typical Operating Characteristics
for a
glitch immunity graph.
MAX6710
IN_
V
TH_
V
TH_
RESET
90%
10%
t
RD
t
RP
Figure 2.
RESET
Output Timing Diagram
Applications Information
Reset Output
The MAX6710
RESET
output asserts low when any
monitored IN_ voltage drops below its specified reset
threshold and remains low for the reset timeout period
(140ms minimum) after all inputs exceed their thresh-
olds (Figure 2). The output is open drain with a weak
internal pullup to the monitored IN2 or V
CC
supply
(10µA typ). For many applications no external pullup
resistor is required to interface with other logic devices.
An external pullup resistor to any voltage from 0 to 5.5V
can overdrive the internal pullup if interfacing to differ-
ent logic-supply voltages (Figure 3). Internal circuitry
prevents reverse current flow from the external pullup
voltage to IN2.
The MAX6710 is normally powered from the monitored
IN2 supply when all input voltages are above their
specified thresholds. When any supply drops below its
threshold, the reset output is asserted and guaranteed
to remain low while either IN1 or IN2 is above 1.0V.
IN2 = +3.3V
+5V
100kΩ
IN2
V
CC
RESET
RESET
MAX6710
GND
GND
Figure 3. Interfacing to Different Logic-Supply Voltage
V
INTH
Adjustable Thresholds
The MAX6710 offers several monitor options with
adjustable reset thresholds. The threshold voltage at
each adjustable IN_ input is typically 0.62V. To monitor a
voltage >0.62V, connect a resistor-divider network to the
circuit as shown in Figure 4.
V
INTH
= 0.62V x (R1 + R2) / R2
R1
R2
V
REF
= 0.62V
or, solved in terms of R1:
R1 = R2 ((V
INTH
/ 0.62V) - 1)
R1 = R2
V
INTH
(
0.62V - 1
)
Figure 4. Setting the Auxiliary Monitor
6
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