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10
Maxim Integrated
Micropower, Single-Supply, UCSP/SOT23
Comparator + Precision Reference ICs
MAX9038–MAX9043/
MAX9050–MAX9053
Detailed Description
The MAX9038–MAX9043 and MAX9050–MAX9053 feature
single/dual, low-power, low-voltage comparators 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 refer-
ence, (MAX9038/MAX9039/MAX9040/MAX9041/MAX9050/
MAX9051 consume only 40A of supply current, while
the dual comparators with reference (MAX9042/
MAX9043/MAX9052/MAX9053) consume only 55A 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 curvature-
correction 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 lim-
its. Input bias current is typically 1.0pA if the input volt-
age 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 exponentially as the input volt-
age exceeds the supply rails.
Comparator Output Stage Circuitry
The comparators in these devices contain a unique
output stage capable of rail-to-rail operation with loads
up to 8mA. Many comparators consume orders-of-mag-
nitude more current during switching than during
steady-state operation. However, with this family of com-
parators, 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 switching frequency approaches 1MHz.
This characteristic reduces the need for power-supply
filter capacitors to reduce glitches created by compara-
tor switching currents. Another advantage realized in
high-speed, battery-powered applications is a substan-
tial increase in battery life. The MAX9038 is an open-
drain 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 resis-
tors using positive feedback (Figure 1). Use the follow-
ing procedure to calculate resistor values:
1) Calculate the trip points of the comparator using
these formulas:
and
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:
VV
R
RR
TL
REF
=
+
1
2
12
VV
R
RR
TH
REF
CC
REF
=+
()
+
2
12
MAX9038–MAX9043
MAX9050–MAX9053
OUT
IN+
IN-
R2
R1
VIN
VREF
VCC
VEE
VCC
Figure 1. Additional Hysteresis
VV
V
R
RR
HYS
TH
TL
CC
=
+
2
12