MAX6461–MAX6466
Applications Information
Interfacing to Different Logic Voltage
Components
The MAX6463 and MAX6466’s active-low, open-drain out-
put versions can be used to interface with a different logic
voltage than V
CC
, as shown in Figure 1. This output struc-
ture sinks current when OUT is asserted. Connect a
pullup resistor from OUT to any supply from 0 to 6V.
Select a resistor value large enough to allow a valid logic
low (see the Electrical Characteristics) and small enough
to register a logic high while supplying all input current
and leakage paths connected to the OUT pin.
Hysteresis
The MAX6461–MAX6466 feature internal hysteresis that
creates two trip points: one for rising supply voltage
and one for falling supply voltage. The hysteresis pre-
vents the output from oscillating (chattering) when V
CC
is near the voltage threshold.
Transients Immunity
These devices are relatively immune to short-duration
and falling V
CC
transients (glitches). The Typical
Operating Characteristics show the Maximum Transient
Duration vs. Threshold Overdrive graph, for which OUT
is not asserted. The graph shows the maximum pulse
width that a falling V
CC
transient typically might have
before the devices are asserted. As the amplitude of
the transient increases, the maximum allowable pulse
width decreases.
Ensuring Valid Output Down to 0V
When V
CC
falls below 1V, the MAX6461/MAX6464 out-
put sinking capability is reduced. Therefore, high-
impedance CMOS logic inputs connected to OUT can
drift to undetermined voltages. This presents no prob-
lem in most applications, because most circuitry is
inoperative when V
CC
is below 1V. In applications
where OUT must be valid down to ground, add a pull-
down resistor to ground so any stray leakage currents
flow to ground, holding OUT low. Select a resistor large
enough not to load OUT and small enough to pull OUT
to ground. For most applications, 100kΩ does not load
OUT and pulls OUT to ground.
Ultra-Low-Power Voltage Detectors and
µP Supervisory Circuits
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