Detailed Description
The MAX9038–MAX9043 and MAX9050–MAX9053
feature single/dual, low-power, low-voltage compara-
tors and a precision voltage reference. They operate
from a single 2.5V to 5.5V (MAX903_/MAX904_) or
2.7V to 5.5V (MAX905_) supply. The single compa
rators with reference, (MAX9038/MAX9039/MAX9040/
MAX9041/MAX9050/MAX9051 consume only 40μA of
supply current, while the dual comparators with reference
(MAX9042/MAX9043/MAX9052/MAX9053) consume
only 55μA of supply current. Their common-mode input
range extends 0.25V beyond each rail. Internal hysteresis
ensures clean output switching, even with slow-moving
input signals.
The output stage employs a unique design that minimizes
supply current surges while switching, virtually eliminating
the supply glitches typical of many other comparators.
Large internal output drivers allow rail-to-rail output swing
that can sink and source up to 8mA of current.
The precision reference uses a proprietary curvaturecorrec-
tion circuit and laser-trimmed thin-film resistors, resulting in
a temperature coefficient of less than 30ppm/°C over the
extended temperature range and initial accuracy of 0.4% (A
grade). The reference output voltage is set to 1.23V in the
MAX9038/MAX9039, 2.048V in the MAX9040–MAX9043,
and to 2.500V in the MAX9050–MAX9053.
Comparator Input Stage Circuitry
The devices’ input common-mode range extends from
(VEE - 0.25V) to (VCC + 0.25V). These comparators may
operate at any differential input voltage within these limits.
Input bias current is typically 1.0pA if the input voltage is
between the supply rails. Comparator inputs are protected
from overvoltage by internal body diodes connected to the
supply rails. As the input voltage exceeds the supply rails,
these body diodes become forward biased and begin to
conduct. Consequently, bias currents increase exponen-
tially as the input voltage exceeds the supply rails.
Comparator Output Stage Circuitry
The comparators in these devices contain a unique out-
put stage capable of rail-to-rail operation with loads up to
8mA. 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. The Typical Operating Characteristics
graph Supply Current vs. Switching Frequency shows
the minimal supply current increase as the output switch-
ing frequency approaches 1MHz. This characteristic
reduces the need for power-supply filter capacitors to
reduce glitches created by comparator switching cur-
rents. Another advantage realized in high-speed, battery-
powered applications is a substantial increase in battery
life. The MAX9038 is an opendrain output comparator
that can be used in logic-level translation or many other
applications where voltage level translation is important.
Applications Information
Additional Hysteresis
These comparators have ±3mV internal hysteresis.
Additional hysteresis can be generated with two resistors
using positive feedback (Figure 1). Use the following pro-
cedure to calculate resistor values:
1) Calculate the trip points of the comparator using
these formulas:
CC REF
TH REF
V V R2
VV R1 R2
−
= +
+
TL REF
R2
VV 1
R1 R2
= −
+
VTH is the threshold voltage at which the comparator
switches its output from high to low as VIN rises
above the trip point. VTL is the threshold voltage at
which the comparator switches its output from low to
high as VIN drops below the trip point.
2) The hysteresis band will be:
3) In this example, let VCC = 5V and VREF = 2.5V:
HYS TH TL CC
R2
V VVV
R1 R2
=−=
+
Figure 1. Additional Hysteresis
MAX9038–MAX9043
MAX9050–MAX9053
OUT
IN+
IN-
R2
R1
VIN
VREF
VCC
VEE
VCC
MAX9038–MAX9043/
MAX9050–MAX9053
Micropower, Single-Supply, UCSP/SOT23
Comparator + Precision Reference ICs
www.maximintegrated.com Maxim Integrated
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