Detailed Description
The MAX9117/MAX9118 feature an on-board 1.252V
±1.75% reference, yet draw an ultra-low supply current
of 600nA. The MAX9119/MAX9120 (without reference)
consume just 350nA of supply current. All four devices
are guaranteed to operate down to +1.6V. Their com-
mon-mode input voltage range extends 200mV
beyond-the-rails. Internal hysteresis ensures clean out-
put switching, even with slow-moving input signals.
Large internal output drivers allow rail-to-rail output
swing with up to ±5mA loads.
The output stage employs a unique design that mini-
mizes supply-current surges while switching, virtually
eliminating the supply glitches typical of many other
comparators. The MAX9117/MAX9119 have a push-pull
output stage that sinks as well as sources current. The
MAX9118/MAX9120 have an open-drain output stage
that can be pulled beyond V
CC
to an absolute maxi-
mum of 6V above V
EE
. These open-drain versions are
ideal for implementing wire-OR output logic functions.
Input Stage Circuitry
The input common-mode voltage range extends from
V
EE
- 0.2V to V
CC
+ 0.2V. These comparators operate
at any differential input voltage within these limits. Input
bias current is typically ±0.15nA if the input voltage is
between the supply rails. Comparator inputs are pro-
tected from overvoltage by internal ESD protection
diodes connected to the supply rails. As the input volt-
age exceeds the supply rails, these ESD protection
diodes become forward biased and begin to conduct.
Output Stage Circuitry
The MAX9117–MAX9120 contain a unique break-
before-make output stage capable of rail-to-rail opera-
tion with up to ±5mA loads. Many comparators
consume orders of magnitude more current during
switching than during steady-state operation. However,
with this family of comparators, the supply-current
change during an output transition is extremely small.
In the Typical Operating Characteristics, the Supply
Current vs. Output Transition Frequency graphs show
the minimal supply-current increase as the output
switching frequency approaches 1kHz. This character-
istic reduces the need for power-supply filter capaci-
tors to reduce glitches created by comparator
switching currents. In battery-powered applications,
this characteristic results in a substantial increase in
battery life.
