MAX9100/MAX9101
+1.0V Micropower SOT23 Comparators
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Open-Drain Output (MAX9101)
The MAX9101 has an open-drain output, which can be
pulled up to +6.0V above ground independent of the
supply voltage. This is typically used with an external
pullup resistor, facilitating interface between mixed logic
voltages. Alternatively, multiple open-drain comparator
outputs can be connected in a wired-OR configuration.
Applications Information
Low-Voltage Operation: V
CC
= 1V
The minimum operating voltage is +1.0V. At lower sup-
ply voltages, the input common-mode range remains
rail-to-rail, but the comparator’s output drive capability is
reduced and propagation delay increases (see the
Typical Operating Characteristics).
Internal Hysteresis
Hysteresis increases the comparators’ noise margin by
increasing the upper threshold and decreasing the
lower threshold (Figure 1). This hysteresis prevents the
comparator from providing multiple poles when driven
with a very-slow-changing signal.
Additional Hysteresis
These comparators have 1.0mV internal hysteresis.
Additional hysteresis can be generated with two resis-
tors using positive feedback (Figure 2). Use the follow-
ing procedure to calculate resistor values:
1) Calculate the trip points of the comparator using
these formulas:
and
V
TH
is the threshold voltage at which the comparator
switches its output from high to low as V
IN
rises
above the trip point. V
TL
is the threshold voltage at
which the comparator switches its output from low to
high as V
IN
drops below the trip point.
2) The hysteresis band will be:
V
HYS
= V
TH
- V
TL
= V
CC
3) In this example, let V
CC
= +5V and V
REF
= +2.5V:
and
4) Select R2. In this example, we will choose 1kΩ.
5) Select V
HYS
. In this example, we will choose 50mV.
6) Solve for R1:
where R1 ≈ 100kΩ, V
TH
= 2.525V, and V
TL
= 2.475V.
Board Layout and Bypassing
A power-supply bypass capacitor is not normally
required, but 100nF bypass capacitors can be used
when the supply impedance is high or when the supply
