Micropower, Ultra-Small, Single/Dual/Quad,
Single-Supply Comparators
MAX9021
1
2
3
4
5
—
—
—
—
—
—
—
—
—
—
—
—
PIN
MAX9022
—
4
—
—
8
1
2
3
5
6
7
—
—
—
—
—
—
MAX9024
—
11
—
—
4
1
2
3
5
6
7
8
9
10
12
13
14
Pin Description
NAME
IN+
VSS
IN-
OUT
VDD
OUTA
INA-
INA+
INB+
INB-
OUTB
OUTC
INC-
INC+
IND+
IND-
OUTD
FUNCTION
Comparator Noninverting Input
Negative Supply Voltage
Comparator Inverting Input
Comparator Output
Positive Supply Voltage. Bypass with a 0.1µF capacitor to GND.
Comparator A Output
Comparator A Inverting Input
Comparator A Noninverting Input
Comparator B Noninverting Input
Comparator B Inverting Input
Comparator B Output
Comparator C Output
Comparator C Inverting Input
Comparator C Noninverting Input
Comparator D Noninverting Input
Comparator D Inverting Input
Comparator D Output
Detailed Description
The MAX9021/MAX9022/MAX9024 are single/dual/
quad, low-cost, low-power comparators that consume
only 2.8µA and provide a propagation delay, tPD, typi-
cally 3µs. They have an operating-supply voltage from
2.5V to 5.5V when operating from a single supply and
from ±1.25V to ±2.75V when operating from dual power
supplies. Their common-mode input voltage range
extends from the negative supply to within 1.1V of the
positive supply. Internal hysteresis ensures clean out-
put switching, even with slow-moving input signals.
Applications Information
Adding Hysteresis
Hysteresis extends the comparator’s noise margin by
increasing the upper threshold and decreasing the
lower threshold. A voltage-divider from the compara-
tor’s output sets the trip voltage. Therefore, the trip volt-
age is related to the output voltage.
These comparators have 4mV 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) Find the trip points of the comparator using these for-
mulas:
VTH = VREF + ((VDD - VREF)R2) / (R1 + R2)
VTL = VREF(1 - (R2 / (R1 + R2))
where VTH is the threshold voltage at which the com-
parator switches its output from high to low as VIN
rises above the trip point. VTL is the threshold volt-
age at which the comparator switches its output from
low to high as VIN drops below the trip point.
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